Ecology of the vegetation of Veracruz - Gómez-Pompa 1973 by JPZ.

VEGETATION-AND VEG-ETATIONAL HISTORY OF NORTH ERN LATIN AMERICA PAPERS PRESENTED AS PART OF A SYM POSIUM, " VEGETATION AND VEGETAT IONAL HISTORY IN NORTH ERN LAT IN AMERICA", AT TH E AMERI CAN INSTIT UTE OF BIOLOGICAL SCIENCES MEETJN G,S. BLOOMINGTON, IN D. (U.S.A.), 1970

edited by

ALAN GRAHAM Departmelll of Biological Sciences, Ken/ State University, Kent, Oflio (U.S .A.)

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ELSEVIER SCIENTIFIC PUBLISHING COMPANY Amsterdam - London- New York

. 1973

Contents Preface . . . . . . . . . . . . . . . . . .

Chapter 1. The Vegetation of the Antilles RICHARD A. HOWARD Summary . . . . . . . . l ntroduct iOJl . . . . . . . Vegetation types in the Antilles Coastal formations . Lowland formations Montane forma tions Qrigins of the existing vegetation of the Antilles Relationships and distribution of the Antillean vegetation Disjunct distribution patterns in the Antilles . . . . . Distribut ion patterns wit hin the islands . . Long-distance 1elationships and disjunct distribution patterns Conclusions References . .

5 8 12 16 17

29 31 34 37 37

Chapter 2. A-Paleoclimatic Interpretat ion of the Eocene Floras of Southeastern

North America DAVID

D ILCHER

Summary . . . . . Introduction . . . Individual components of the fl ora Identification to modern taxa Evolution of the fossil taxa . Relation of range and ecological tolerance. Community structure . . . . . . . . . . . . Stability through time . . . . . . . . . Separation into equivalent modern communities Foliar physiognomy . . . . Leaf-margin analysis . . . . . . . . Leaf-size analysis . . . . . . . . . Interpretation of foliar physiognomy . Application to this nora Additional evidence Wood . . . . . . . Pollen . . . . . . . Paleoclimatic interpretations References . .

40 41 4t 42

43 44 44 45

46 48

50 53 54 55 55 55 56 57

Chapter 3. G eographical Relationships ofthe Flora of Mexican Dry Regions J. RZEDOWSKI Suillmary . Introduction

61 61

f X

CONTENTS

CONT ENTS

Relationships between diOcrent arid zones of Mexico Relationships with other arid zones of the world Relationships with zones of non-a rid climate . Conclusions References . . . . . . . . . . . : . â&#x20AC;˘ .

63 1;6'

70 71

Clrapter 4. Ecology of the Vegeta tion of Veracruz ARTURO G6MEZ-POMI'A

Summary . . . . Introduction . . . Physical condi lions Topography Climate Soils . Vegetation . . Forests Selvas . High sclvas . Low selvas . Grasslands . Arid or semi-arid vegetation Secondary vegetation References . . . . . . . . . . .

73 73 73 73 75 85

89 94 105 106 118

128 135

145 147

Chapter 5. The Phytogeography and Vegetation ofChiapas (Mexico)

149

149 150 154

155 155 158 161 163 164

Chapter 6. The Vegetation of Panama: a Review D UNCAN M. PORTER

Summary . Introduction Climate Soils Man Vegetation .

Vegetation maps . . . Koppen macroclima tes Holdridge Life Zones Human innucnccs . . . Darien forest types . _ . A summary of plant comnumiti<.,-s Incipient Forest . . . _ Early Secondary Forest Late Secondary Forest Liltoral Forest . . . . Thorn Forest _ . . . . Deciduous Seasonal Forest . Savanna .. . . . . _ . S<tltwatcr Swamp Forest . Saltwater Riparian Forest. Brackish Swamp Forest _ llrackish Riparian Forest Freshwater Marsh . . . Freshwater Swamp Forest Frcshw<tter Riparian Forest . Monsoon Forest . . . . Evergreen Seasonal Forest Premontane Rain Forest Cloud Forest Elfin Forest Acknowledgements ~ References . . . .

17 1

171 172 173 174 175

175 177 179

182 183 184 185 187 187 187

189 189 190 192

193 197

197 198 199 199 200

Chapter 7. Phytogeographic History of the Isthmus of Panama during the Past

DENNIS E. B REEDLOVE

Summary . . . . . . . Introduction . . . . . . Phytogeography of Chiapas . Vegetational formations ofChiapas Description of the formations . Optimum forma tions. . . . Seasonal format ions . . . . Wet-land forest formations . Treeless formations References . . . . . . . . . . .

167 167 169 170

170 171

12,000 Years (A History of Vegetation, Clima te, and Sea-level Change) ALEXANDRA S. B ARTLETT AN D ELSO S. BARGHOORN Summary . . . . . . . . . . Introduction . . . . . . . . . Northern South America . Southern Central America Panama . . . . . . . Geological history of Panama .. Pre-Quaternary history . . Late Quaternary and Recent history Physiography' and climate of Panama . Climate of the Canal Zone The present vegetation of Panama Preparation ofsamples . . . . Preparation techniques . Preservation of samples The pollen diagrams . . . . . Theoretical considerations The Gatun Basin diagrams The modern pollen rain . Climatic change in Panama . . . Identification and nomenclature of the fossil pollen .

203 204 .-

204

206 207 208

208 209

211 211

212 216 219

219 2 19 2 19

222 225 228

229

J. RZEDOWSK I

Gomez Pompa, A .. Hcrn{tndcz l';tllares, L. and Sousa S<inchcz. M., 1964. Estuclio fotoccologico de Ia cucnc:1 intcrmcdia del Rio Papaloapan. In: Comribtrciotres a/ Esttrclio Emlu~:ico de /a.1· Zonas Ctilido-ltrimeda., de Mt!xico- ln.rt. Nacl. llll'est. For., Mexico, Ptrbl. Esf'ec., 3, pp.37- 90. Gonzalez Quintero, L., 1968. Tipo.1· de Ve~:etaciun del Valle de Mt•zqtrital, H~:o. Departamento de l'rehistoria, lnstituto Nacional de Antropologia e l-listoria, Mexico, D.F., 49 pp. Graham, E. H., 1937. llotanical studies in the Uinta Basin of Utah and Colorado. Anu. Cam. Mus., 26: 1-432. Gray, A. und Hooker, J .D., 1880. The vegetution of the Rocky Mountain region, and a comparison with that of other parts of the world . Bull. U.S. Ceo/. Geogr. Snn•., 6:1 - 77. Johnston, I. M., 1924. Expedition of the Cali(ornia Acadeniy of Sciences to the Gulf of Califo rnia in 1921 - The botany (the vascula r plants). Proc. Calif Amd. Sci. 4 Ser., 12:95 1- 1218. Johnston, I. M., 1940. The fioristic significance of shrubs common to No rth and Sout h American deserts. J. A mold Arborctum,21 :356-363. · Krliger, 0., 1934. Die Gmmineenf/om im nordamerikanischen wul siidameriktmi:>c!Jen Tmdcengebiet. Thesis Phil. Fak. Friedrich Wilhelms-Univ., Berlin, 63 pp. LeSueur, H. , 1945. The ecology of the vegetation of Chihuahua, Mexico, north of parallel 28. Unil•. Texa.1· Pub/., 452 1: 92 pp. M<tdrigal Sanchez, X., 1967. Contribuci6n a l conocimiento de Ia ccologia de los bosqucs de oyamcl (Abies religiosa (H.B.K.) Schl. et Cham.) en cl Y<tlle de Mexico. lust. Nne/. l111·est. For., Mexico, Bo/. Tee., 18: 94 pp. Maysilles, J. H., 1954. Floral Relationships of the Pine Forests of West em Durttugo, Mexico. Thesis, Univ. M ich., Ann Arbor, Mich., 165 pp. M iranda, F., 1955. Forrnas de vida vegetalcs y cl problema de Ia dclimit<lcion de las zonas aridas de Mexico. In: Mesas Redout/as Sabre Problemas de las Zonas Aridasde Mexico. Ediciones Jnstituto Mexicano Recursos Naturales Renovables, Mexico, D.F., pp.85- 119. Morello, J., 1958. La provincia fitogeografica del monte. Opera Lilloana, 2:1-155. Ozenda, P., 1958. Flore du Saham Septemriona/ et Central. C.N. R.S., Paris, 486 pp. Preston, F. W., 1962. The canonical distribution of commonness and rarity. Ecology, 43: 185- 215; 410-431. Rzedowski, G. C. de, 1960. Notas sobre Ia nora y Ia vcgctacion del cstaclo de Sun Luis Potosi, 7. Vegetaci6n del Valle de San Luis Potosi. Acta Cieut. Potos., 4:5-11 8. Rzedowski, J., 1962. Contribucioncs a Ia fitogeografia floristica e hist6rica de Mexico, I. Algunas consideraciones acerca del clcmcnto endernico en Ia flora mexicana. Bol. Soc. Bot. Mex., 27 : 52-65. Rzedowski, J., 1966. Vegetaci6n del cstado de San Luis Potosi. Ac·ta Cient. Potos., 5:5-291. Rzcdowski, J. and MeVaugh, R., 1966. La vegetacion de Nueva Galicia. Coutrib. Uuil'. Mich. Herb., 9:1 - 123. Shreve, F., 1942. The desert vegetation of North America. Bot. Rev., 8:195- 246. Shreve, F., 1951. Vegetation of the Sonoran Desert. Cam.lust. Was/1., Pub/., 591: 1- 192. Smith, C. E., J r., 1965. Flora Tehuacan Valley. Fie/diana Bot., 4:107-143. Standley, P. C., 1916. Comparative notes o n the floras of New Mexico and Argentina. J. Wash. A cad. Sci., 6:236- 244. Wiggins, !. L., 1961. The o rigins and relationships of the land flora. In: The Biogeography of Baja Califomia and Adjacent Seas, 3. Terrestrial and Fresh-water Biotas. Syst. Zoo/., 9:148- 165. Wiggins, !. L., 1964. Flora of the So no ran Desert. In: F. Shreve and I. L. Wiggins, Vegetation ond Flora of the Sonoron Desert. Stanford Univ. Press. Stanford, Calif., pp.l89-1740.

! C!Japter4

Ecology of the Vegetation of Veracruz1 ARTURO G6MEZ-POMPA

Departmemo de Botdnica, lnstituto de Biologia,

Unil'crsida~/

Nacionul Autunoma de Mexico

Su01mary A summary is presented of recent studies and unpublished data from current investigations on the ecology and vegetation of Veracruz, Mexico. The types of plant communities are defi ned and their occurrence related to prevailing ecological facto rs such as cl imate (temperatu re, precipitation), altitude, soil types, and the effect of man on the natural vegetation. Introduction Veracruz IS the most varied of all the states of Mexico. This variat ion resulted out of its latitudinal extent, its complex topography and the variety of its soil types. The state of Veracruz is located on the Gulf of Mexico and extends from 17°10' to 22°20' N. It occu pies 62,820 sq. km being a strip of land approximately 800 km in length by 50- 150 km in width.

Physical conditions Topography

Veracruz is composed mainly of lowland areas; the altitude of most of the state is less than 300m (Fig.!). However, the state contai ns an important branch of the mountain system of central Mexico, which is a part of the Sierra Madre del Este and also·part of the Cintur6n Neovolcanico that crosses the country. These mountains are also very important because they include the highest peak in Mexico, Mt. Orizaba ' Flora de Veracruz, Contribution no.4. A joint program of the l nstituto de Biologia of the Universidad Nacional Aut6noma de Mexico and the Arnold Arboretum and Gray Herbarium of H arvard University, to prepare an ecological floristic study of the state of Veracruz, Mexico. (See Anales Ins/. Bioi. Univ. Nac. Auton Mex., 41, Ser. Bot., I: l -2). The author is indebted to .Bernice G. Schubert and Lorin I. Nevling for their valuable suggestions to the manuscript. N icolas Aguilera critically reviewed the part of the text concerned wit h soils. Margarita Soto made valuable comments on t he climate of Veracruz. This paper was partially supported by a grant from the National Science F oundation {GB-20267X).

A. G6MEZ-I'OMPA 98'

ECOLOGY OF THE VEG ETATION OF VERACRUZ 96'

(Citlaltcpetl), which reaches an altitude of 5,747 m. Another important mountain system is the Sierra de los Tuxtlas composed or a series of volcanic cones extending to ca. I,700 m in attitude. At the sout hern end of the state there are a few unexplored branches oft he Sierra Mad re del Sur which have an altitude of I ,000 m. The remainder of the state is more o r less flat with the exception of a small sierra located ncar the 21st parallel and reach ing 700 m.in altitude (Sierra de Tantima).

State of Veracruz Alt i metric mop

22'

(alti t udes above sea level)

Clima/e

{From U SAF nav i gation chart)

22'

20'

-/--!--

cotre de

(J\

-:0 -:0

-j-

20 '

b-:0

16'

--1-

(I'

1000

(I'

r 18'

300 500 1000 sca l e

100

200 KM

96'

Fig.l. Altitudinal map of Veracruz.

.94'

As a result of topographical variations a nd latit ude, climatic factors are rather variable in Veracruz and explain, in part, many of the distribu tion patterns of the vegetation types and of their component species. The climates of Veracruz have been st udied by Garcia ( 1970). H er system of climate classification is extremely useful from the biological point of view, because it takes into consideration those factors to which vegetation responds, such as amount o f rainfall during the dry season, and temperature variation between the coldest and warmest months. As f will use her work in climatic references to the vegetation types, a map of the climates is included (Fig.2). On the following pages I shall discuss some oft he climatic fac tors with special e~np h asis on their importance to vegetation d istribution. Temperature. This fac tor has an important effect on the vegetation in relation to its variation in an altitudinal gradient. Most of the state is warm with average temperatures of more than I8Â°C (Fig.3). T he average values as such do not mean much in understand ing species d istribution; th e temperature values that are more important arc the extremes, especially the minimu m extreme temperatures, because they serve as filters for the distribution of species. The most important factor to note is that there is only a small gradient in average monthly extreme minimum temperatures, which are lower at h igher latitudes. _Previously latitude has not been considered ecologically significant at lower altitudes in the tropics, but it seems that in the state of Veracruz it is of great importance. If we study the absol ute minimum temperatures the problem becomes clearer (Fig.4) : there are very low temperatures in the northern latitudes in comparison with the south, and the vegetatio n corresponds to this temperature gradient. The ranges of many species in Veracruz seem to be determined by winter temperatures, because other facto rs (mainly soils and precipitation) seem not to excede t he limits of tolerance of most of the species. This problem is also interesting because it opens the possibility of doing some experimen tal studies on the effect of low temperatures on populations of extreme tropical lowland species, in relation to the adaptation of other species to this same facto r. I have not yet found evidence of a direct relationship between the distribution of plant species and extreme high temperatures in Veracruz. High temperatures seem to be more closely related to dryness and are important for this reason.

ECOLOGY OF THE VEGETATION OF VERACRUZ

A. G6MEZ-POMPA 96'

h·cczing temperat ures (below O"C) a rc frequen t in the mountains and absent in the lowla nds (Fig.S) with the exception o r Tantoyuca in the northern portion of the sta te (Soto, 1969).

96'

St ate of Vera c ruz Types of c I i mote 22'

!S.§j

AwO

ffiillll

AW2

~A I (m)

g~:;~

~Aw l

~Am -ET H EFH mcwlo Cwlb

(ill)~:~~ El ~~\~;" lillHll t1f~<'~) ~\<;.))gr;~) [ill

22'

~:~~~ ~::~~~

20'

Rainfall. Rainfall is the most important ecol o g i ~.:a l factor allccting the vegetation of the state at any given altitude. There are two aspects to be considered : o ne is the total amount o f rainfall, and the other is its dislribulion t hroughou t the yea r. If we look at the patterns of lola! raii!fcdl ( Fig.6), it is evident that t here are great extremes : fro m less than 500 mm in the tem perate desert to more t han 4,000 mm on the lower slopes of the sierras. The ma in reason for such a distributi on is the di1ection of the humid trade winds of the northeast that change in direction and in ascent on contact with the special topography of the continen t. The consequent cooling produces heavy p recipitation on the windward side and scarce precipitation on th e other side. Th is is the cau~e of the upper deser ts and the lowland dry areas. The northern dry zone is produced by the Sierra de T a m aulipas; the semi-arid zone near the port of Veracr uz is produced by the Sierra de Chiconquiaco just below the 20th parallel ; a nd a semi-arid zone on its southwest side is produced by the Sierra-de los Tuxtlas. The other aspect of rainfall is the distribulion of rain throughout the year. ln most parts of the state there are two well-marked seasons: the rainy season and the dry season. In the middle of the rainy season there is a temporary decrease in precipi-

20'

18'

16'

sca 50

100

200KM

94'

Fig.2. The climates of Veracruz. (After Garcia, 1970.) Garcia, in her description used the Jist of symbols given on p. 77.

Hum id dinwte~i: A = hoi humid C = Iemperate E =cold A(C) or (A)C = hot temperale ETH = cold at high alii tudes EFH = very cold or wilh ice all the year, al high alii tudes m = summer rains with monsoon influence Am(f) =summer rains wilh monsoon influence, winter rains higher than 10.2 % Cf(m) = precipitation of the dries! mOnlh higher Ihan 40 mm, with the percentage of winter rains higher than 18% w = summer rains regime w0 = summer rains regime with P/Tiower than 43.2 w1 = summer rains regime with PIT between 43.2 and 55.3 w, = summer rains regime wilh P/Thigher Ihan 55.3 a= warm summer, with the average temperature of the warmest monlh above 22•c b = long and cool summer, with the average Iemperature of the warmest month above 22•c c = short and cool summer, with the average temperature of the warmest month lower than 22°C and less than four months with the average temperature above 1o•c Dry clima/es BW =very dry BS, = dry k = temperate with warm summer, average annual temperature between 12• and t s•c, temperature of the warmest m onth above I8°C k' = temperate with cool summer, average annual temperature between n• and t s •c, temperature of the wa nnest month lower than ts•c

.,.

A. G6MEZ-POM I' A

78 99'

96'

97 '

22"+

St ate of Verac r uz Ther mi c zones

Avera ge an n ual temperature (•C )

(ill]

very hot mor e tha n 26•

~ ~ ~

hot

IIllllll

sem i cold

•

s~m i

22'- 2!!' ho t

21"

CO l r.:c,..-<:cn 00< OcutQ O• 0 Btttcto o• 1 Boca Scxtt<OSIQ 0 18 COPwii'IU 020 Cd Alemdn

09 :! Pt1ttot, los

09> Rinclll'\o:Jo 096 Rrncon Poeheco

Oll

090 I 06 10 9 110

OIJI'tm;o, RUM:hO

0 31 :iron t il, Lo

18 ' - 22 '

h mp e ratt 12' - 18°

5'- 12' between - 2 ' a nd s•

very cold l e ss than - 2•

~O"C

~ ''"'·: <r<

0<0 Hrda 14jOi rl ldn 0 41 ~k90, [I 0'3 kylocro dl lo

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052

I. C

Noutl0

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G.JtrO!'ft 1' lOII\CIO

.....

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Son N.colo' SCfllfOQO dt to Ptfio

Sont!ll90

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112 So n bo~Uo, hlo dt 114 So!edud dt Ootllodo 117 Toncocl'lojlo

118 Ton1111a

0 5 0 JOIIrj)On 051 .H,Y, COIIOfllO

16 '

00. Polfr.or, El

087 Pdft.AQ 080 Poi'K)IIIlo 09 1 J\)1o Reo

021 CO\omotoopoll 0)0 CltCI..alctolapan

Qj!)

co ld o r

08 4 O: IUoolllo

Cotou..tl~t~

I ZI Tt ccluno 124 TtM(:oot

o>• Loudtopcn O>G l o-.o Fino 0 57 No~.,os

126 Teuchodcan

0>8 Mcntos. los 059 Mont.o Fabio Allonw~o OGO t.IOIO ~ UII'IOMS 061 M alo T.nohiO 063 N orliloet Cit kl Torte OOG rllt'IOI1U61l 070 Morwo S.. 012 tll)tzc•Of190 082 Otohllon

129 Tfototafpon 130 Tt<llu (.Oyatl Ill

1~7

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,.....

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09 3 Ororonnt

.. 0

IJO' t

19'

IB"

19"

16'

·-Isc o le

.,.,

f7•

100 96'

Fig.3. Thermic zones of Veracruz. (After Garcia, 1970.)

2.00Km .

97'

...

+ .,.

...

Fig.4. Minimum extreme temperatures measured from 1921 to 1910 in stations lower than 300 m ; there are two very distinct areas: in the northern portion with temperatures close to o• and in the south with temperatures around 1o•c.

A. GOMEZ-I'OMPA 98"

ECOLOGY OF H IE VEGETATION OF VERACRUZ

96" 97"

St ate of Veracruz

State of Veracruz

22" ~

Annua l ra i nfal l (mm)

Num ber o f d ays per year with frost

22"

20"

less t han 800

fZZ1

800-1000

1000-1200

1200-1500

1500-~0 00

2000-2500

2500-3000

EZ:8

3000-4000

more than 4000

-!-

-+ 18°

20"

-+ 0

Son A.TUXtla

18"

19"

18"

sca

17"

100 96°

18"

-1-

200KM ~4·

Fig. 5. Frosts in Veracruz. (After Soto, 1969.)

s c a 1t 50

tation (see F ig.l4) causing a few days of dry and warmer weather called "canicula" (Mosifio and Garcia, 1966). Its ecological importance has not yet been evaluated. From the ecological viewpoint the most important season is the dry season, which is also the colder season. T he amount of rain during the dry season varies greatly, and on this variation depends the type of vegetation in the region : evergreen,

97"

100

96"

200KM

95"

Fig.6. Rainfall in Veracruz. (After Garcia, 1970.)

r I

A. G6MEZ-POMPA

ECOLOGY O F TH E VEGETATI ON OF V ERACRUZ

35' Stat io n Ah.a liln

State of Veracruz P l uv iomet r ic regimen Ro i n1oll

symbo l s

r2g i m~ n

summor

le.ss t ha n 5 •1.

UTID

E§l

5-10.2 • /o

Feb M ar: Apr May Jun Jul.

~2~-

AUQ Scp Oct No,. Dec

-9

Coo tepee

9 .6

COrdoba

5.3

Coscomatepec

6.8

Cuaut o tolopan

• .6

Dob ladcro

Je ss than 18 •J.

20'

9 .9

Coot za coa lc o

Durango, Rancho

3.9

Isla l o bos

Jo loc ingo

7.7

Jaltipon

6.9

Mi sontlo

15.4

Mot z.orongo Nautlo

4.9 13 3

O ri za ba

OtatiU6n

4.9

O zuluomo

6.3

Pa nuco

4.8

Papontfa

18'

scc fc: 0

100

20 0 KM 95°

A~~t~~f

•l-4~

18 n3

~~J~

16J

_JZ9__ _

600

2610

1~.

9__

2'))0

10_ -

9.7

Perote

6.7

Po t r ero

5.4

Rinconada

4.0

Sn. Andres Tuxtl o

4.6

Sn. Juan Evangelist a

5.4

So ledad de Doblado

3.6

Tanto yuca

6.8

Tlocotalpan

5.6

Tux pan

8 .5

Venustiano Co.ron.za

5.6

Ve raCt:"UZ

3.0

....

. 6 . ..•9

_,3_ 12

__7_. 12

:!972

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!0_ . 17- 17_ -'~!...-

17 20 24 ------ . --- 25 '2'66

211

1 6~

28 6

22 e;e

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6 __ 2'~"

19, 1

Jll\32'

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18'

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9 16

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20 -~Q. . ._3_2_ 21_ J:n

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4 9'-

227

1617

8 7fi

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370

182 )

712

11? __1_8_ _ _29 ___15 1279

1148

I()?)

2658

.?.?. __I9l.__

1970

94'

Fig.7. Rainfall regimen in Veracruz. (After Garcia, 1970.)

· Fig.8. Distribution of dry days (above) in different stations of Veracruz. These figures can be compared with the figures of rainfall for each month (below).

A. G6MEZ-POMPA

ECOLOG Y OF THE VEGETATION OF VERACRUZ

semi-evergreen, or deciduous. The rain during thi s period is not brought by the trade wind s but by polar air masses (called "nortes") that bring rain, and in some areas, low temperatures. Garcia (1970) has made a classilication of these winter rains using the percentage of winter rains in relation to total rainfall (Fig.7). This value is of i;11portancc because there is a close relation between the total amount and the amount at the 98'

Stat e o f

Veracruz Number of

dry season. However, the value that is of direct interest is the total number of dry days throughout the year and the distribution or these days in each month (Fig..&). This value can be used t~ explain the presence of certain vegetation types in "wrong" places.

Fog. Another form of precipitation that is seldom taken into account is fog. In large areas in the mountains of Veracruz, fog is cha1acteristic, and the name "cloud forest" is appropriate for these areas. The average number of days wi th fog is a good measure and is indicated in Fig.9. It is evident that these areas have higher humidity and less illumination, two factors that can explain their characteri stic flora.

96'

22'

Snow. Snow rarely occurs in Veracruz except on the highest peaks. It has been reported from several stations in the mountains above 1,200 m alti tude. Even though snow is not regular in altitudes just above 1,200 m, its occasional presence may explain the absence or various species and genera in these localities. Among the most important staiions reported with snow (Soto, 1969) arc Atzalan, Jalacingo, Orizaba, and Perote.

days per

y e ar with f og

22'

Soils 20 '

-../.... I

18'

20'

-/_ I

16'

scale

100

96'

Fig.9.

200KM

94'

Number of days with fog in Veracruz. (After Soto, 1969.)

In contrast with the knowledge of climates, the so ils of Veracruz are very poorly known and a soil map of Veracruz is still needed. However, there are some isolated ~o i l studies helpful toward an understanding of the soil variation in the state. Soils are produced by the interaction of climate, organisms, rocks, and also by topography and time. W e know the climate ofVeracruz and we have also some information about the rocks, but we know very little about the action of organisms in soil formation. The great diversity of soils in Veracruz comes in part from the diversity of parent rock materials available, and as this is combined with a great diversity of climates, the result is a great number of different edaphic habitats. For example, basaltic lava flows can be found in very different.climates of Veracruz from t he very humid, warm lowlands of Catemaco where a tall evergreen selva develops, to the drier warm lowlands north of Martinez de Ia Torre where a lowland oak forest grows, to the temperate regions above Jalapa where pine forests are found in lava flows. In all three instances the parent rocks are very sim ilar, and the climate determines the difference in vegetation. The geology of Veracruz is well known and some distribution patterns of species in similar climates follow the geological patterns as will be discussed later. In any particular climate, the soils determine the changes in the distribution patterns of species and therefore of the vegetation types. I shall discuss what is known of Veracruz soils in relation to each of the vegetation types. The soils of Veracruz can be divided roughly into the following Great Groups: red and yellow lateritic soils, ando soils (yellow and brown), vertisols, lithosols (incl. regosols), calcimorphic, saline, alluvial, and swamp soils.

TABLE I ANALYSIS OF A SOIL PROFILE1 1N A PINE FOREST

Depth

Horizon

( Pinus har/ll'egii)

Colour

(em)

when dry

ON TH E SO UTHW ESTERN SLOPE OF T HE PICO DE OR IZAI3A IDENTI FIED AS AN ANDO SOIL (CRYANDEPT) •

Appar. density

Relat. density

Sand

Silt

Clay

(%)

(% )

(%)

Texwre

(1:2.5)

when wet

(3,740 M ALTITUDE); THE SOIL WAS

Total C.fo. Org. C/N C.E.C. AlloN (% ) mauer (mequiv.f phane ( %) (%) 100 g)

-- -~-------------·~ · ~

0-5

All

10YR 5/ 1 grey

IOYR 2/ 1 black

1.20

2.24

58.0

35.1

6.9

sandy loam

6.2

0.253

3.57

8.12

21.0

xxxx

5-15

Al2

!OYR S/1 grey

10YR 2/ 1 black

1.31

2.32

61.3

31.9

6.8

sandy loam

6.3

0.184

2.45

5.61

19.0

xxxxx

15-25

A12

lOYR 5/ 1 grey

IOYR 2/ 1 black

1.30

2.31

60.7

32.5

6.8

sandy loam

6.2

0.172

2.55

5.84 ·

19.1

xxxx

25-35

A13

lOYR S/ 1 grey

IOYR 2/ 1 black

1.22

2.22

57.3

36.3

6.4

sandy loam

6.2

0.226

3.06

7.01

25. 1

xxxx

35-45

Alb!

10YR 5/ 1 grey

10YR 2/ 1 black

1.23

2.25

63.6

27.7

8.7

sandy loam

6.2

0.203

2.74

6.26

22.3

xxxx

45-55

Alb!

IOYR S/ 1 · grey

I OYR 2/ 1 black

1.15

2.22

6 1.0

28.3

10.7

sandy loam

6.2

0.242

3.24

7.42

25.1

xxxx

55-65

Alb!

lOYR 5/ l grey

10YR 2/ 1 black

!.II

2.23

57.2

32.1

10.7

sandy loam

6.2

0.235

3.36

7.70

27.2

xxxx

65-15

A1b1

10YR 5/ l grey

IOYR 2/ 1 black

l.l 4

2.29

6.1.7

29.9

8.4

sandy loam

6.2

0.206

2.94

6.75

25.1

xxxx

75-85

A lb!

lOYR 5/ 1 grey

lOYR 2/ 1 black

1.04

2.27

54.4

36.1

9.5

sandy loam

6.2

0.177

2.72

6.24

23.3

xxxx

85-95

A l b2

IOYR S/ 1 grey

JOYR 2!1 black

1.1 3

2.25

57.4

33 .5

9 .1

sandy loam

6.3

0.156

2.45

5.61

~::!. .'2

xxxx

95- 105

Alb2

!OYR 5/ 1 grey

IOYR 2/1 black

1.18

2.36

55.6

35.7

8.7

sandy loam

6.3

0. 145

2.21

5.06

21 .8

xxxx

105- 11 5

A 1b2

IOYR5/ l grey

IOYR 2/ l ,black

1.1 8

2.40

55.6

37.7

6.7

sandy loam

6.3

0.127

1.98

4.52

23.5

xxxx

11 5-1 25

A l b2

JOY R 5/ 1 grey

lOYR 2/1 black

1.39

2.44

63.0

30.3

6.7

sandy loam

6.3

0.091

1.42

3.26

17.2

xxxx

125-135

A lb2

!OYR 5/l grey

IOYR 2.5/ 1 black

1.35

2.54

61.6

3 1.9

6.5

sandy loam

6.3

0.086

1.21

2.76

17.1

xxxX

JOYR 5/ 1 grey

!OYR 2.5/ 1 black

1.1 7

IOYR 5/ 1 grey

IOYR 2.5/ 1 black

1.18

?' Cl

0 3: 1;-l

0"" 3: ;

~ ·

135-145 145-155 155-165 165-175

A lb3 Al b3 Alb3

1.29

2.5Y 5/ 2 greyish brown

IOYR 3/ 1 very dark grey

1.30

185-195

!OYR 5/2 !OYR 7/2 light grey greyish brown

195-205

A l b4

IOYR 6/ 2 light grey

!OYR 7/2 IOYR 5/ 2 ligh t grey gt·eyish brown

!OYR4/ I dark g rey

38.7

8 .7

sandy loam

6.3

0.166

2.06

4.70

27.4-

XXxX

2.37

60.8

29.0

I 0.2

sandy loam

6.3

0. 171 2.32

5.30

27.2

xxxx

2.43

63.3

29.7

7.0

sandy loam

6.3

0. 136

1.69

3.86

23.3

xxxx

-n

:I:

1.40

2.49

2.52

57.1

59.8

36.1

44.7

4 .8

5.5

sandy loam

6.4

0.095 . 1.21

0.046 0.36

2. 78

0.83

18.8

I 1.2

xxxx

2) ~

xxxx

~ 0 z 0

-n

1.36

2.52

44.1

50.7

5.2

silty loam

6.3

O.Q35

0.25

0.49

·10

10.4

xxxx

< m

1.30

2.46

4 5.6

47.5

6.9

sandy lo am

6.4

0.087

0.88

2.02

17.5

xxxx

;;o

- - - -- ------- - 1After J o h nson

-< -l

IOYR 2.5/ 1 black

52.6

8 r Cl

!OYR 5/ 1 grey

175-185

2.35

~- ,

> (")

c:: N

(1970)

A. G6M EZ-POMPA

ECOLOGY OF T HE VEGETATION OF VERACRUZ

Red and ye/fow laterilic soils. These soils are fo und basically in the warm or semiwarm areas and have many variations. They arc characterized by their red or yellow color and the low con tent in silica compou~1ds in the upper horizons (A), which on the ot her hand, arc rich in sesq uioxides of aluminum and iron (Mohr a nd Van Ba ren, 1954; sec Table V).

leaching of salts fro m the surround ing mountains that accumulate in a closed wate rshed and, in thi s very dry region, prod uce a lw.lophytic envi ronment. As in ot her salt deserts, the vegetation is unique. T he othe r sal ine soils are those of the coastal areas, which also support a unique flo ra (sec f-"ig.34).

A11do soils (yellow and brown). The ando soils have been found mainly in cold areas of Veracruz (Johnson, 1970). They are fo und also in temperate regions of Veracruz and even in lowland areas as in the Los Tuxtlas region (Whiteside, 1960). These soils are derived from volcanic ash and are very rich, supporting a permanent agricultu re with two or three crops a year (Tables I and X). Planosols and vertisols. These soils, about which very little is known, are fou nd in restricted localities in the state on very flat topography. Some unique vegetation types develop in them, such as some palm stands and low selvas. In many cases these soils have a paler horizon that has been called pseudogley, caused by a high water table (glcysols). Many of them arc inundated in the rainy season and dry very drastically on the upper surface in the dry season (Fig.29,30). Âˇ Litlrosols (incl. regosols). These soils a re a complex group ; the only common factor among them is that there are no soil horizons developed, only the parent rock in different stages of decompo5ition. T he two most important rock soils are the volcanic and the limestone soils. The volcanic soils are distributed widely in the state. They sometimes sustain a very rich flora because of the many microenvironments pt ed uced among the rocks. The limestones are also fou nd in several localities and in different thermic regimen. The karstic topography of many limestone areas is caused by the high precipitation that dissolves the limestones irregularly giving them their characteri stic rough topography. The true soils are very thin and located between the rocks. They are rich in calcium compounds, which have an important influence on the floristic composition (Gomez-Pompa et al., I964b). The rock soils prod uce a drier environment locally because they have high drainage and poor water retention in comparison to deep soils in the same macroclimate. Calcimorphic soils. Calcimorphic soils are soils derived from calcareous rocks and are, therefo re, rich in calcium compounds. When the limestone is broken and decomposed, the soil developing has large amounts of calcium compounds. These salts and others accumulate in the upper horizons in soils of the dry regions. On the other hand, in time, calcimorphic soils of wet regions can evolve in different directions in relation to the climate (Aguilera, 1958). Saline soils. Saline soils are known from one locality on the border with the state of Puebla between Perote and Alchichica (see Fig.33). This soil is produced by the

Alluvial soils. These soils may be of very diverse origins, the only factor common to them being located nea r nowing water. They do not have well-defined horizons, and their other characteristics may vary wit h the climate or with the parent rock. These soils support a vegetation that di ffers remarkably from the vegetation of neighbouring areas in the same macroclimate. Swamp soils. Swampy soils in Veracruz are not very common and may be divided into two groups: the mangrove swamp soils (see Fig.37) and the inland swamp soils. On ly a few profiles have been studied in relation to vegetation studies (Vazquez, 1971 ).

Vegetatio n The vegetation of Veracruz is a result of the combination of all the environme ntal variables that have been discussed, in additi on to many ot hers of which we know very little, such as the paleobotanical history of the area, the effect of man on the vegetation, and the ani mal/plant interactions . By this I mean that the amount of available in formation permits some correlations be tween similar ecological requirements of species, thus allowi ng us to make a classification of the vegetation of the area. At the same time, the lack of information on many other ecological variables expla ins the absence of correlation and the inconsistencies which make such a classification seem very incomplete. I will restrict my di scussion to the primary vegetat ion, which is the vegetation that appears to be the most stable one in the area, where there are no signs of probable replacement by other vegetation types in the near fu ture. Many of these types are disappearing quite rapidly because of h uman activities, and secondary vt'getation is fast becoming the dominant vegetation in the ~t ate. The classification to be fo llowed is the one proposed by Miranda and Hernandez X. (1 963), with slight modifications to incorporate some intermed iate types found in the state. Some of the names will be in Spanis h only because translation of them can lead to errors (Gomez-Pompa, 1967). With in each type only the most characteristic species will be mentioned. A few quadrats that have been studied elm ing the ecological survey of the Gulf Coast region of Mexico (Anonymous, 1960- 1969; Gomez-Pompa et al., J964a) will be used to illustrate the structure of the vegetation and to typify it. T he data that will be incl uded are a synthesis of available material. The details for each region will be omitted as much as possible because these are, or will, be discussed in regional studies n ow in progress and planned to include the whole state.

A. G6M EZ-POMI>A 0

::; :0 I

cb :0

E <t

,..

~ fi' E <(

iii

,..

-E e-

w 1<(

w Q.

l :0

XXX X

";{

~ X

0 3- ;:"' ~ u u u

::> I

::>

<f)

,.. 0:

0 ...J

~==-==::oc-

~ 0 ;: 1-

r - ÂˇÂˇ - -

z<(

<f)

0 ...J

E <(

ECOLOGY OF THE VEG ETATION OF VERACRUZ

Since vegetation is the-resu lt or the com bi ned acti on of nu merous environme ntal factors on the s pecies available in an area, there arc numerous very different correlation patterns. The most obvi ous one is t h e tempera t ure/vegetation relationship in the mountai n zonat io n, but we should not be misled by t his as oth er facto rs such as fog and rainfall also change with altitude, and it i ~ no t easy to separate them. Therefo re, it is necessary to emphasize t hat each vegetation type has to be treated separately and st udied independe ntly. There arc some vegetation types found only in a ce rtain restricted cli mate, and o thers fou nd in a wide va riety of climates. There are ty pes of vegetation restricted to certain soil types wh ile others live in many difl'ercnt soil types. An attempt to show some of the correla tions of vegetation types with climate that I recognize for Veracruz is illustrated in Fig. I0. As there is some confusion in co nnection with the hiera rchical arrangeme nt of vegetation and the terminology used by di fTercnt a uthors, I will use only the term "vegetat ion type" for a group of wild plants ph ysiognomically recognizable as a unit, and more or less stable (primary in our sense). Within each vegetation type, several comm unities or associations exist, and l define them as grottps of plants in a restricted area having si milar ecological require ments and a similar macroclimate. The problems and theoretical discussions that are the basis of this poi nt of v iew have been di ~cus sed elsewhet e (Gomez-Po mpa, 1966, 1967). In recent time there have been s_eve ral studies related to the vegetation of Veracruz prepared by the ecological survey p rogram of the lowlands of the Gulf of M exico undertaken by the "Comision de Dioscorea s of t he National Institute o f Forestry Research o f Mexico" (Anonymo us, 1960-1969 ; Gomez-Po mpa et al. , 1964a). I n addition to the data gathered-a nd still being med, the Comision has produced, directly or ind irectly, several papers including data on the vegetation of Veracruz (GomezPompa et al., 1964b; Gomez-Po mpa, 1966; Pen nington and Sarukh!m, 1968 ; Sousa, 1968; Toledo, 1969; Chiang, 1970; Leon and Gomez-Po mpa, 1970 ; Cuanalo and Aguilar, 1970). Another project that has promoted several recent studies of vegeta tion is the Flora of Veracruz program (Gomez-P ompa and Nevling, 1970) of wh ich the work presented in th is paper is a part. Several o ther vegetation papers have been produced as a part of th is program (So to, 1969; Lot, 197 1; Vazquez, 1971; Ramos, 1971). Additional studies related to the vegetation of Veracruz which should be mentioned are the general paper on the classificat ion o f t he vegetation of Mexico by Miranda and Hernandez X. (1963) in which Veracruz is ment ioned in their treatment of the types. T he work of M iranda and Sharp ( 1950) o n the clo ud forests includes a description of many sites in Vetacr uz. A paper by Williams ( 1939) on the t rees of the southern portion of the state is also important. A fe w additional papers were consulted ; t hey will be mentioned in the description of the types related to them. In order to help explain the physical rela tionships among the different vegetation types, a series of diagramma tic vege tation profiles will be presented from different geographic regions of the state.

....

TABLE II KEY FOR THE VEGETATION TYPES OF VERACRUZ

-------,---

Vegetation dominated by trees (woody plants of more than 4 min height) B.

A very dense tree community with several dominant tree species; frequen tly with severalty pes of climbing plants (Selva)

Dominant trees without spines D.

Evergreen E.

Dominant trees of more than 30 m of height

(4) High e11ergreeu selra

EE. Dominant trees Jess than 30m of height (usually less than 10m)

(7) L ow evergreen selra

DD . Trees with deciduous leaves F.

s: rn

Trees higher than 15m G.

t;'l

Trees of more than 25 m

{ 5) High semi·e1·ergreen sell-a

GO. Trees shorter . .

{6) lvfedium semi·e1·ergreen seh•a

FF. Trees lower than 15 m H.

? 0·

More than 75% of the trees have deciduous leaves.

3 :!:; ~

(9) Lo"· deciduous selra

H H . Less than 50% of the trees have deciduous leaves

(8) Loll' Sl!llli·e1·ergreeu seha

CC. Many dominant trees with spines .

( 10) Loll' thom selra

BB. A more open tree community, with few dominant tree species (usually one or two) and few climbing plants (forest) I. Trees branched

J. More than 50% of the trees deciduous . . . . . . . . . • . . . . ( 3) Deciduous forest

JJ. More than 75% of the trees evergreen K.

Land tree con1numitics

L. With broad leaves

• . . . . . . . . (2) Broad-leaved f01·est

LL. Wit h needle or scale leaves -'1

Needle leaved .

( l) Need/e-/ea1·ed forest

MM. Scale leaves . .

{I) Scaltt-leaved forest

KK. Swamp tree communities

( 19) Mangrove forests

II. Unbranched . . .

I II) Palm ;·tands

AA. Vegetation dominated by shrubs or herbaceous pla nts N.

Land communities

In coastal regions with marine influence . . ( 2 1) Coastal dune., 1·egetation m

00. Not in coastal regions P.

Mainly dominated by herbaceous plants

In lowland warm areas . . . . . ( 12) Sa1·anna

-< 0

QQ. In upland temperate and cold areas

"l1

-1

In saline soils . . . . .

( 14) Saline gr·as.rland

RR. Not in saline soils

S. In cold areas above 4,000 m . . . . . . . . {20) Paramo 1·egewtiou SS. In temperate areas below 4,000 m . . . . . . . ( 13) Temperate grassland

PP. Not dominated by·grasses T.

Great ab'undance of plants with rosette leaves. . . . . . . ( 15) Nolina·Heclrtia-Agaredesert

TT. Abundance of thorn shrubs {16) Thorn scrub

:I:

m <

2l ~

0 "l1

< rn

"' "'c

()

NN. Communities partially or totally in water part of the year or all the year . . . . . . . . . ( 17,18) Swamp 11egetolion t)'J)es or (22) Aquatic 11egetation types 10

A. G6MEZ-POMPA

Fon'!lts The term fores t incl udes those vegetati on types that arc arborea l and whose dominant species arc few, frequently only one or two. These occu r mainly in the temperate a nd cool mountain regions where the humidity is enough to sustain a tree com munity. In these regions the low winter temperat tJres are the most important ecological fll ter responsible fo r the poor diversity of tree species in contrast with the selvas in the lowlands. Forests in the lowlands arc found only in areas in which some extreme edaphic conditions have become important limit ing factors; the most widespread tree communi ties in these lowla nds are the seh·as.

(I ) Needle-/eared forests and scale-/em·ed foresrs. In compariso n wi th other states of Mexico, t he pine forests of Veracruz are relatively poor and limited in extent, but almost all the main climatic subtypes recognized (Gomez-Pompa, 1965) are present in the state. The highest and coolest pine forest in the state is the one formed by Pinus hart· IVegii growing within the li mits of the paramo vegetation in t l~e highest mountains, at an altitude of between 3,000-4,000 m or more (Balls, 1939; Johnson, 1970). The flora of this forest is not well known and the only reliable ecological info rmation available is that produced by Johnson. The climate of these communities is unknown beca t;se there is no meteorological sta tion at this altitude, but by extrapolation from other mou ntai ns at the same latitude, the average mean temperatu re must be in the range of 4-11 <c. A soil profi le known at this altitude may be..seen in Table I. Some of the common plan ts reported (Johnson, I 970) fro m the area are the following: Dominant species Pinus lrart wegii Lind!. Other species Abies t•e/igiosa (HBK.) Schlecht. et Cham. Alchemil/a vulcanica Schlecht. e t Cham. Arenaria bryoides Willd. Arenaria serpens H BK. Castilleja sp. Cerastium orithales Schlecht. Ceraslium vulcanicum Schlecht. Cnicusjorul/ensis HBK. Eryngium proteafiorum Delar. Ha/enia nudicaulis Mart. et Gal.

Halenia paucijlora Hems!. Lupinus elegans HBK. Lupinus moll/anus H BK. Lupinus vagina/lis Cham. et Schlecht. Oxylobusarbutifolius(HB K.) A. Gray Pentstemon gemianoides (HBK .) D on Pitws montezumae Lam b. Potentilia richardii Lchm. Stenanthium frigidum K unth Stipa ichu (Ruiz et Pav.) Kunth

In the more protected areas in the higher altitudes near the tree line, a forest of Abies religiosa can be found. This fo rest has been reported from the Mt. Orizaba (Johnson, 1970) and a similar one probably exists in the Cofre de Perote. There are no data

ECOLOG Y OF T HE VEGETA TlON OF VERACRUZ

available on the floristic compositio n of these forests, but we may expect them to be not very diiTcrcnt from neighbouri ng p ine forests. At lower altitudes, between 2,000 a nd 3,000 m, there are pine forests in several areas of the slate. T hese tempera te pine forests are the most common type in Mexico, and most of our species of pi ne have been descri bed from them. In these areas t he pine forests arc mixed with oak forests forming local ecological mosaics possibly due to local humidity gradien ts, soil type, or human activities. The cl imate in these areas is mainly temperate and humid (C) and may contain different subtypes. Some climatic data from a station located in this vegetation are shown in Fig. II.

Latitude 18•43' Longitude 97"19' Altit u de 1500.00m A C U LTZ ING O Aver age annual t empera t ure 17.4•c To t al annual romfoll 723.7mm

700

E ~

'E .5

5c 0

" "..:>

::'"'

!0 c

200

:;:

100

Fig. II. Climatograph of a station in a pine forest region.

The soils of these pine forests are n ot known. I have fou nd only one soi l profile description from forests of Pinus pseudostrobus above Or izaba and it probably corresponds to an ando-sol. T his forest is interesting becau~e it is located within the limits of a warmer vegetation, and many species of the lowlands come to form a part of it. The following species have been reported from this community (Chiang, 1970) :

A. G6MEZ-POM!> A

ECOLOGY OF THE VEGETATION OP VERACRUZ

Domhuuu :,pecie.v

Pinus pscudost robus Lind!. Other species Alnus ar;:uta (SchlcchL) Spach. A nmdinella deppeana Nccs Calea integrijiJ/ia (DC.) Hems!. Caleamanicata (Schlecht.) Bent h. ct Hook. Calea urtidfolia (Mill.) DC. Crnsea ca/oceplwla DC. Diphysa f/oribwrda Pcyr. Eupawrium asclrenbomiamm1 Schauer. Eupatorium morifoliwn Mill. Gnap/w/ium braclryplemm DC. Quer·cus ctmdicam· Nee Quercus xa/apcnsis Humb. La;:ascea lrelianthifo/ia HBK. Lantana lrhpida H BK.

LitJpia hypo/cia Briq. Lit.wa glaucescen,· H13K. Pam tlresi.1· .rerrulata (Sw.) Mcz Pteridium aquilimn11 (L.) Kuhn Rapanea myricoides (Schlecht.) Ltmdell Rubn>· adenotriclws Cham. ct Schlecht. Saurctuiu pedrmculata Hook. Senecio gmndifo /ius Less. Senecio ,,·draJ]ireri Schultz Bip. Smilax .rpi11osaMill. So/anumtorvum Sw. Temstroemia syll'atica Schlecht. ct Cham. Vemonia deppeana Less.

Several pine fo rests have develo ped on the lava beds above Jalapa. The largest seems which the follo wing species are found:

w be one of Pinus teocote in

Dominant species

Pinus teocote Cham. ct Schlecht.

Pinus pseudostrobus Lind!. Othe1· species

A;:m·e xaltl/u:nsis Roezl. Arenaria /ycopodiodes Willd. Bacdwri>' COI((erta H 0 K. Biden.l"triplinen•ia HI3K. Castilleja longibracteata Mart. et G al. Cheilmrthes microphy/la Sw. Comus disci/lora DC. Comusexcelsa HBK. Holenia bre••icomis(HBK .) Don

Lytlrmm ocinifoliwn (DC.) Koehne Ma/axis soulei L. 0. Williams Monoc/wetum jloribundum (Schlecht.) Naud. Oxa/i.> comicu/ota L. Oxalis decaphylla HBK. Quercu.l' caucliams Nee Rumex acetosel/a L. Relbwriw11 hypoca111ium Hems!.

Fig.l 2. Forest of Pinus cembroides in the region of Perote (Veracruz) with No/ina fXII'I'if/om. (Photo C. Ranios.)

TEZIUTLAN - TLAPACOYAN - NAUTLA

A large area of temperate pine forest is found near Huayacocotla on the border of the state of H idalgo; this is dominated by Pinus teocote, and the fo llowing species have been found in it: Domina/11 species Pinus rudis End!.

Pinns teocote Schlecht. et Cham. Other species

Alchemil/a pectiuara HBK. A/mrs arguta (Schlecht.) Spach. Arbutus glandulosa Mart. et Gal. Ascyrum hypericoides Linn. Baccharis conferta HBK. Brunella vulgaris Greene Chimaphi/a maculata (L.) Pursh. Cor11us disci/lora DC. Comus excelsa HBK. Erythraea macra11tha Hook. et Arn. Galium UIICinu/atum DC.

Leucothoe mexicana (Hems!.) Swall. Lophosoria quadripimwta (Gmel.) C. Chri. Pinguicula cauda/a Schlecht. Pteridium aquilimrm (L.) Kuhn Quercus casta11ea Nee Quercus candicans Nee Quercus crassifolia Humb. Quercus mexicana Humb. Ranuncu/us dichotomus Moe. et Sesse Spilanthes americana (L.f.) Hier. Temstroemia sy/vatica Schlecht. et Cham.

LIOUIDAMBAR FOREST

HICH $ (MI ·EYERG RUN

tilLVA

OAK FOREST

MAifCitOv.E S WA M P

Fig.I3. Vegetation profile Teziutlan- Naulla showing the boundaries of the forest of Pinus strobus var.

chiapensis.

A. G6M EZ-POM PA

ECOLOGY OF T HE VEGET ATION OF VERACRUZ

In the contact zone between the subhumid temperate and the temperate arid vegetation, on t he border wit h the state of Pucbla ncar Perote (Ramos, 1971), sma ll populations of Pinus cembroides a re found at 2,500 m (Fig. l2). The floristic composition of this community will be discussed also wit h the arid vegetation because its fl oristic composition is similar to other types, except in the more protected areas in which this species grows with Quercus micropily/a and Sophora secwuliflora which have similar

Dominant species PinuJ strobus L. var. chiapensis M:trtincz Other species Bro.l"inwm a/icastrum Sw. Humpeu ilrtcgerrima Schlecht. Bnmcllia mexicmw Standi. Quercus exec/sa Licbm. Cymhea costaricensis (Kuhn) Domin Sauvagesia erecta L. Ncp!telea mexicana (Schlechi. ct Cham.) Tryon

Jn the T uxtlas region on the eastern slopes of the volcano Santa Marta, a forest of

Loti t ude Long itude Al t it ude · PUENTE

Pinus oocarpa is found at an altitude as low as 500 m, mixing at this altitude with some

19'56' 97'12' 510.00m

species from the lowlands and some from the deciduous fo rest above, such as the fo llowing:

HENR IQUEZ

Domi11a11t JiJecies

Average annual t em perature 22.9°C Total annual rainfall 2266.5 mm

Piuus oocarpa Schiede Otlrer species 700 600

Alibcrtia ed1tlis (L. Rich.) A. Rich. Bulbostylispapillosa Kukcnth. Byrsonima crassifolia (L.) DC. Clethra macrophylla Mart. et Gal. Crotonnit e11s Sw. Croton repens Schlecht. Leucothoe mexico11o (Hems!.) Swall.

Liquidambar macmplryllo Ocrst. Mosquitoxylonjamaicense Krug. et Urban Myrica cerifera L. Paspa/um pectinatum Nccs Pa.<palum plicatulum Michx. .Saurauia serrata DC. Zamia loddigesii Miq .

T his forest grows in red lateritic soils with low organic content. It also grows at higher altitudes on the same volcano, but no floristic study has yet been undertaken. Other species of pine that have been found in Veracruz are: Pinus ayacalwite Ehrenberg Pi11us leioplrylla Schlecht. et Cham.

M A

Fig.J4. Climatograph of a station very close to the area where Pilws strobus var. chiapensis occurs.

ecological requirements. This community grows on very thin calcimorphic soils. Also in this area small patches of a Scale-leaf Forest dominated by Juniperus deppeana are found living also in this transitional region. In t he region of Tlapacoyan a forest of Pinus strobus var. chiapensis develops in a very restricted area at a n altitude of 500 m (Fig.13). T his species grows in the contact area of the high selvas with the deciduou~ forests having a mixture of species from those vegetation types. The climate of the region can be extrapolated from the data of the nearest town (Fig.14). The species that have been reported from this forest (Miranda and Sharp, 1950) are the following:

Piuus montezumoe Lamb. Pinus paflila Schlecht. et Cham.

(2) Broad-leal'ed forests. These forests a re found ma inly in the temperate regions of the state, although a few are found in the warm lowlands. The most important are the oak forests which have an enormous ecological diversity. More than forty species are known to occur in Veracruz, many-·of them important components of many forests. Other types of broad-leaved forests have been reported from the state, but m ost of t hem are SJllall and may be lumped with other vegetation types. The oak forests of Veracruz may be divided into two main climatic groups: the· temperate and the warm. T he temperate oak forests are to be found in the same general area as the pine forests in this climate, forming a vegetational mosaic. T he two forests share a great number of species and, in some cases, may be treated better as pine-oak forests rather tha n as separate, distinct types. The evergreen oak forests of higher altitudes have not been studied from the ecological point of view. The oak forests from the warm areas are better known, and a more integrated scheme can be presented. These forests occupy large parts of the lowla·nd areas in the

100

A. G6MEZ-I'OM PA

ECOLOGY Or: TH E VEGETATIO N OF VERACRUZ

siHtc, and as a group may be considered a relict vegetation type. In recent geological ti mes, during the last glacial ion, the temperature decreased and certain groups of plants from the temperate mountainous regions invaded parts of the lowlands and mixed with more tropical taxa. During these times many taxa probably were eliminated by the lower temperatu res, pr ovid ing ecological niches that were then occupied by tempera te elemen ts such as Quercus, Piuus, Podocarpus, Myrica, and Cletlrra. When the area warmed, many of these groups retreated to the cooler mountains or died in the competition with better ada pted tropical groups that returned or spread from their restricted areas (warmer protected places). Bu t some of the temperate elemen ts found niches where tropical species did not thrive, such as drier places and poorly drained soils. Here the temperate plants have survived up to now. There is no direct evidence that thi s is true, and the whole idea is derived from indirect evidence of distribution patterns (Miranda, 1959 ; Gomez-Pompa, 1966; Toledo, 1969, and others) as discussed elsewhere in this paper. The oak forests of the lowland areas in Veracruz are found in very different cl imates, from drier areas in the northern part of the state to very wet po.rtions of the south. In the region of Poza Rica, a fores t of Quercus oleoides is found on Java flows. This fores t is up to 25m tal l and has a rich herbaceous flora. The following species have been found in this area :

.-i M

'li

<'I I

C"!

101

Dominant species Quercus oleo ides Cham. et Schlecht. Other species Alcltomea latifolia Sw. Byrsonima cra.nifalia (L.) DC. Dendropanax arboreus (L.) Decnc et Planch. Ficus maxima P. Mill.

Sapium/atcrijforum Hems!. Tapirira macrophylla Lundell ZinOII'iewia htlegerrima Turcz.

In the Misantla region (Gomez-Pom pa, 1966) several quadrats were studied under different soil conditions. The soil analysis for an oak forest in this region is in Table III. Sovonno ot C r-r~CMtio cujctc w ith Curatetlo

americana

"'"' c!,c!, "'

c!,

G-

"' "'

Sem i-deciduous sel ves

Selva of Glnoria ttudlfloro

Ook t ore

stot

Oucrcvs

otcoidcs

Selvo o( rerminollo amDzonlo

l torestof Ook ISelvaofiSelvo of Trrml. Broslmumwith Quercus ,olio nio

E 0

.-..

. ;!2

..,.. .."'

>,0 ... ...

o.,

-o

Ac/lros

olcoidts omazo.

Fig. l5. Vegetation profile from Los Naranjos, Veracruz- Temazcal, Oaxaca. The tropical lowland oak forests grow side by side with other vegetation types. Each one occupies a different soil type. (After G6mez-P ompa et al., l964b).

Âˇ

A. G6MEZ-POMPA

102

ECOLOGY OF THE VEG ETATION OF VERACRUZ

103

Another tropica l oak forest is fE*Ifld- in the area of sout hern Veracruz on the bo rder with the sta te o f Oaxaca. This forest grows in red and yellow lateritic so ils with high clay content a nd poor internal drainage. As the to pography is undulating, there is a micro topographical factor giving a catena of soil and vegetation, from t he upper parts covered ma inly by oak forests to the lower parts covered by different selvas (Fig. l 5). The following species have been fou nd in this fo rest : Dominant species Quercus oleoitb Cham. ct Schlecht. Otltcr species Byrsonima crmwfoHa (L.) DC. Cocco/oba borbadcnsis Jacq. Conostegia xalapensis(Donpl.) D. Don Cnratclla americana L. Genipa cantlo H 0 K .

Ptcridimn aqui/imm1 (L.) Ku hn Quercus spp. Waltlteria brel'ipesTurcz. Xylosmaf/exuosum (H BK.) Hcmsl. Zuekmia guidonia (Sw.) B ritton ct Milsp.

(3) Deciduous forests. The deciduous fo rests occur in Veracruz only in the temperate Latitude 19' 9' Longitude 95'57' Altitude 1344.00m HUATUSCO Average annual t emperature 15.7Â°C Total annual rainfall 1745.0mm

Fig.17. A Liquidambar macrophyl/a forest in Huatusco, Veracruz.

F ig. 16. Climatograph of a station located within the region of the Liquidambar-Quercus deciduous forests.

and more h umid areas of the mountai ns. One of the most in teresting ecological characteristics of these areas is the frequency of fogs. For this reason they have been called "cloud forests". I n Fig. l6 a select ion of climatic data from a station located in the deciduo us forest region is given. Such forests are usually found a t altitudes between I ,000 and 2,000 m (Fig.l7). In the Sierra de Chiconquiaco, so uth of Misantla, the deciduous forests are dominated mainly by Liquidambar macrophylla mixed with several species of Quercus. These fo rests develop in yellowish soils derived from volcanic rocks. The fl ora is very rich, and there seem to be no sharp differences in the vegetation patterns in this zone. The variatio n in floristic composition is a gradual one following topographic and humidity gradients (Gomez-Po mpa, 1966). This fo rest may be very tall, up to 40 m in height. One of its interesting characteristics, in contrast to other deciduous forests in northern latitudes, is that many species here remain evergreen. The name refers to the dominant species, which have deciduous leaves.

104

A. G6M EZ-PO MPA

ECOL OGY OF THE VEGET ATION OF VERAC RUZ

Other .1pecies

l n this sierr.a the fo llowing species have been no ted:

Al/itroa mexiccma D. E. Stone Carpinuscarolinimw Walt. Eur:eniamexicmw Stcud . Guarea cltidton C. DC. lngalatibmctettiCt Harms 0/medie//a betsdtlericma (Go cpp.) Locscncr Palicuurea galeottiana M arL Phoebe gent lei (Lund .) Stan di. ct Stcycrm. Pithccellobium ••ulctmortntt Sta ndi. ct Steycnn.

Domina/11 .\7Jecie.\·

Liquidombor mocruphylla Oerst.

Querc·us ajfiui>· Schwidw. Other species

Ardisia hyaliua Lundell Be/aria gltmca Hum b. ct Bon pl. Bn mellia mexicana Sta ndi. Caln Jtnmthes karll'inskyana Berg. Carpinus caroliniana Walt. Centradenia sa/ici[olia Brandeg. Cestrum endlicheri Miers Cestrum fasciculattmt(Schlccht.) M iers Clethra macrophyl/a Mart. el Gal. Cleyera .rermlata C hoisy Coccocypselum hirsulum Bartl. Conostegia Mborea (Schlecht.) Schauer Cyatheaful••a (Mart. el Gal.) F ee Deppen purpusii Standi. Diospyros riojae G6mez-Pompa Eugenia tnmcif/ora (Schlecht. ct Cham.) Berg. Fagus mexictma Martinez Heliconia bihai L. Heliconia sc/riedeana Klotzsch et Gkc. flex ••omitoria A it. Juglans pyriformis liebm. Klugia aznrea Sch lecht. Loasa triph)•lla Fuss. Lycopodium cenmum L. Magnolia scltiedeana Schlecht. Marsdenia macrophylla (Humb. et Bonpl.) Fourn.

105

Meliosma alba (Schlech t.) Walp. Nephelea mexicmta !Schlecht. et Ch;un.) Tryon Oreopcmax /iebnwmti M arclw I Peperomia deppeana Sch lecht. et Cham. Peperomia glabella (Sw.) A. Die tr. Peperomia obuwfolia (L.) A. Dietr. Perrottetia longistylis Rose Persea cinera.1·cens Blake Phoebe acuminatissima Lu nd . Podocmpas matuclai Lund. Pnmus tetradenia Koehne Quercusocolet((o/ia Licbm. Riclwrclia scabra L. Rondeletia cttpitellata Hems!. Sah•ia amarissima Ort. Sambucus mexicana Pres! Saurauia ••illosa DC. Solanumlanrifaliwu M iII. Temstroemia sylwt!ica Schlecht. ct C ham. Tetmnema mexicammt Bent h. Tillandsia po/yswchya L. Toumefortia petiolaris DC. Trium[elfa dumetorw11 Schlec ht. Verbena carolina L. Viburmwttiliaefolium (Ocrst.) Hems!. Xylosma jfexuosum ( I-I BK.) Hems I. Weinmmmia pinna/a L.

Pmmts brachybotrya Zucc. Quercuscm-rttgata I l ook. Quercnr pilcwius T rcl. . Sluaneasp. Tulau11w mexictuw (DC.) Don Tricftilia g/abra L. T11111in ia alL pcmiculata Vent. Xylomw quicltense Don. Smi th

A very intriguing questio n concerns the decid uo us character of many of the component species of the forests beca use in these lat itudes the winter is not severe eno ugh to explain t hc_"adva ntage" of the decid uous habit. Al so the humidity is high all year, so a d ry season is not a selective factor. It may be that the deciduous habit is a relict characteristic retained only beca use there has not been strong competition with other tree species. Perha ps the explanation is to be fo und in the winter temperatures, which, although not very low, might explain the absence of t he more tropical tree species very sensitive to tempera ture. On the other hand, the very high humidity and poor light might explain the lack of success o f ot her temperate elements from the forests above. In the Cerro de San Cristobal near Orizaba at an altitude of approximately 1,200 m (Mira nda and Sharp, 1950) a deciduous fo rest of Engelhardia mexicana was found in the central part of the steep nor-t heastern slopes where very deep soils occur. The followi ng species were reported : Dominant opecie>· Eugelltardia mexicana Stan di. Other opecies

In the area near 1-Iuatusco, a decid uous forest was sam pled and a quadrat made {Chiang, 1970) to show its structure. Other species fou nd in th is forest are:

Cletltra quercifolia Lind!. Comus florida L . Deppea grandi/fora Schlecht. Ho/fmannia orizabettsis Standi.

Dominant species

Liquidambm· ntacr·opltylla Oerst. Ostrya virginiana (Mill.) Willd. Rondeletia bourgaei Standi. Senecio grandifolius Less.

Liquidambar macropltyl/a Oerst.

Se/ms

Other species Dussia mexicana (Standi.) Harms Psycho!ria ar. tricltoloma Mart. et Gal. Quercus spp.

Styrax glabrescens Ben t h. Twpinia insignis ( H BK.) T u lasne Zamhoxylum kellermanii P. Wilson

Another important zone of decid uous forest was descri bed by Sousa in the Sierra de los T uxtlas (Sousa, 1968) where he found the following species : Dominant species Liquidambar macrophylla Oerst. Quercus skinneriBenth.

Ulmus mexicana Uebm. Meliosma alba (Schlech t.) Wa lp.

.~ .

In contrast with the forests, the selvas are tree communities which are composed and dominated by several species of trees. There are several vegetation types included in this category which a re m ainly determined by the distribution and total amount of rainfalL Sel vas are the characteristic vegetation types of the tropical lowlands of the world. They have been called rain fo rests and tropical fo rests, but neither of these terms seems to be adequate (Gomez-Ponipa, 1965). The classification of the selvas uses two principal parameters: the height of the communities and the percentage of deciduous tree species.

'! 106

A. GOMEZ-POM PA

Higli seh•as

These are 25 or more m tall and arc fo und in areas wit hout a pronounced dry season and with a total precipitation of more than ca. 2,000 mm. ( 4) High e1·ergreen seh•as. This is the tallest vegetation type in Veracruz, where it grows in the more humid, wa rm areas of the state with precipitation from 2,5005,000 mm or more per year and with few if any dry months. One of its characteristics is that 80% or more of the component species are evergreen, or at least they do not foll ow a definite pattern of leaf fall at one time. This vegetation type is the one known as "tropical rain forest", "rain forest", "wet tropical fores t", "evergreen tropical forest" or combinations of these names. In Veracruz this type of vegetation is found at the lowland flatlands at the base of the mountains a nd at the so uthern end of the state. Jn the Sierra de los T uxtlas it occupies a great portion of the slope at altitudes below 7()0 m. Some meteorological stations are situated in the area where these selvas used to grow, and data from them can be seen in Fig. IS.

These sclvas grow in different types of soils, but most commonly in deep yellow lateritic soi ls (Table V) wit h good drainage. [n the Sierra de los Tuxtlas area they also occur on brown soils derived from volcanic ash and even .on lava beds with soil underneath. In the sout hern portion of the state (Leon C. and Gomez-Pompa, 1970) such communities form a vegetation mosaic with other vegetation types because of soil differences produced by microtopography. There arc many kinds of communities within the vegetation type in these areas, where a small soil difference gives rise t o a differen t combination of speci~s, both in quality and qua ntity, as ca!1 be seen in two quadrats made a few meters apart at different soil levels (Tables IV, VI). Some species characterizing this type are the following: Dominant species Dialium guiwtense'(Aubl.) Sandwich Terminalia amazonia (Gmcll.) Excll. Calophyl!um brasilieme Cam b. Other ;pecies (continued on p. 108) Andira inermis H UK. Brosimum alicnstrum Sv.'. B

l atit ude

18 ° 19'

Lo ngitude

94'25'

Alt i tude

14 m

107

ECOLOGY OF THE VEG ETATfON OF VERACRUZ

Latitude Long itude Altitude COYAM

16'26' 95'00' 340 m E

Ave ra ge annu al temperatu re 23.4°C To t al annual rai nfa ll 44 39.8 mm

CO ATZ ACO AL COS Ave ra ge on nuol t emperature 25.3 °C Tot a l ann ua l ra infall 272 6 .2mm

e.. ~

3 l:'

'E ~

c 0

·:;

2:>

·a.

:5c 0

·;:;

1'0.

"'l:'"

2:>

::;:

Fig.18. Climatographs of stations located within the region of the high evergreen selvas. A. Coatzacoalcos station; B. Coyame station.

3 0

~ ~

E ~

.sc .2

2:>

.... 2

!0c

""'l:' ">

" ~

2:>

:5c 0

::;:

lOS

A. GOMEZ-POM PA

Cephaelis tvmentos11 (A ubi.) Yah! Cupania demata DC. Cymbopetalum baillonii Fries Cymbopetalum penduliflomm (Dtmal) llaill. Cynometmretusa Hr. et Rose Deudropwwx arboretl.l' (L.) Dccnc. et Phmch. Genipa americana L. Guarea chiclwn C. DC. Gum·eatonduzii C. DC. Gnotlerio amplifolia Triana et Planch. flirt ella mcemosa Lam. Jacamtia dolidwula (Donn. Sm.) Woods. Licania hypoleuca Bent h. Licaria peckii (Johnst.) Kostcrm. Matayba oppositifolia (Rich.) Brill on Mortoniodendron sp. Ormosia ist/unensis Standi. Podocmpus grwtemalensis Standi. var. pinetomm (Bart.) Buchh. et Gray

Po.\·oqueria latifolia (Rudge) Rocm. et Schult.

ECOLOGY OF THE VEGETATiON OF VERACRUZ

Pouteria campeclriana (HilK.) B:tehni l'.l'eudo/media oxyphyllaria Donn. Smith Rinorea guatcmalensis (Wats.) Bartl. 1/heedia edu/i.1· (Seem.) Triana ct Planch. Salacia belizen.l'i.1· Standi. Saprwrtlws all'.Jwmi/is Miranda Scheelea liebmmmii Bccc. Simarouba glauca DC. Sloauea tuerckheimii Donn. Smith Sphaeropleris myosuroides (Liebm.) Tryon Stdm!ia apetala (J acq .) Karst Stercn/iamexicana R. Hr. Swietenia macmphylla King Tapirim macrophylla Lundell Trichi/ia hirta L. Trophis mexicamtm (Ucbm.) Bur. Tu11Jinia an·.pcmiculata Vent. Vochysia hondurensi.1· Sprague Xylopia/rlllescenl· A ubi. Zue/ania guidonia (Sw.) Britton et Milsp.

TABLE IV QUADRAT

Domi-

Of HIGH EVERGREEN SELVA OF

Name

IIliilCC

Terminafia 1/1/laZOIIia

Number Freofindi- quency t•iclua/s (%)

JN THE COATZACOALCOS REGION

Maxi- A''erage mum height height {111)

Coverage {m')

Ba.m/ area (cnn

(111)

Termina/ia amazonia

40.0

29.00

15, 11 6.10

582,698.0

Tapirira macrophylla

30.0

(Caobilla) Brosimum terrabanum (Ojochillo)

14.89

1,383.55

23,341.5

20.0

14.20

981.55

14,521.5

Podocmyms guatemalensis

25.0

(Palo de Campana) Jnga sp. (Palo Tinto)

18.33

1,250.51

11,499.0

25.0

25.00

565.45

11,1 82.0

Cupania dell/ala

Hirtella racemosa

(Suchi Amarillo) 2

5 80

12.0

8.94

1,287.60

8,787.5

15.0

8.31

910.55

6,750.5

(Tres Lornos) (Icaco Verde) 8

Dialium guianense

15.0

11.17

742.0 5

5,284.0

(Paque) Guarea sp. (Palo Bejuco)

10.0

7.07

686.80

5,023.0

Sapranthus humilis

15.0

10.80

400.40

4,630.5

23,324.56

673,717.5

Other species (25) Total 1

450

After Leon and Gomez-Pompa (1970).

::: 't

.Q I

I~ iE

>rl

109

110

A. G6MEZ-POMPA

ECOLOGY OF THE VEGETATION OF VERACRUZ

T ABLE VI QUADRAT' OF A I·IIGII EVEHG RHN SI:LVA OF

Dia/ium guianense

The fo llowing species characterize these sclvas: GROWING IN A MORE II UMID SOIL THAN

TilE ONE IN TABLE IV

----· Domilwnce

Name

Nrunber ofindi••iduals

Frel}ftCIICY

(%)

Dominalll species

Maxi- Average mum height height (m )

Coverage

Basal area

(m')

(em')

Bemou/lia/lammea Oliver Bro.rimum a/icasrrum Sw.

Ficrutecolmensis(Licbm.) Miq. Pseudo/media oxyplryllaria Donn. Smith

(III) Dillliwn guianense

Orher species

25.5

7,902.50

124,863.0

28.4

3,392.80

111,911.0

(Paquc) 2

Tcnninalia amazonia

(Suchi Amarillo) Triclri/ia sp. (Caobilla)

25.0

2,136.20

32,713.0

Guatteria amplifolia

15.5

1,040.60

10,617.0

(Palo Calabaza)

Guarea chic/ron

8.3

1,428.30

8,702.5

(Palo de Bejuco) Licania sp. (Mierda de Nino)

25.0

1,258. 10

6,360.5

Dendropanax arboreu.1·

9.4

946.25

6,170.5

(Carne de Pescado) Cupania an·. dentata DC (Palo Colorado)

13.3

646.95

5,140.0

Clusiasp.?

25.0

565.45

3,589.0

10.5

467.20

2,789.0

19,784.35

312,855.0

(Ciempie) 10

Cupania dentala DC (Tres Lemos) Other species (18) Total

200

Ill

• After Leon and Gomez-Pompa (1970).

Three species on this list that need further discussion are Podocarpus guatema/ensis, Quercus oleoides, and Sphaeropteris myosuroides. They seem to be out of place in this type because, with the exception of Sphaeropteris, they have not been found growing in these seivas in any other areas in Veracruz or even in Mexico. I cannot find any environmental explanation for this coincidence. The only possible explanation is that they are relicts of the old community that seems to have grown in these areas in the recent geological past when the .area was cooler. The first two taxa are also found in edaphic communities, such as savannas and oak forest, and even in the lowland pine forests of British Honduras (Lundell, 1937). This lends support to the idea that a cooler and/or drier climate was predominant in this area during the last glaciation. The other area of extensive tall evergreen selvas is found in the lowland5 of the region of the Sierra de los Tuxtlas, where several surveys of the vegetation communities have been made (Anonymous, 1965 ; Sousa, 1968).

Albizzia purpusii Br. et Rose Alchomea/atifolia Sw. Annona muricara L. Annona purpurea Moe. et Sessc ex DunaJ Annona retiwlatt1 L. Andim ga/eollimra Standi. Astrocaryummexicamrm Liebm. Bacrris bacu/ifera Karw. ex Mart. Bactris co/rune Watts Bursera simarubn (Sw.) Sarg. Ceiba pentaudra (L.) Gacrtn. Clramaedorea a/temaus Wend!. Clramaedorea emesti-augr/Sii (H. Wend!.) Oerst. Chamaedorealindeuiana Wend!. Clramaedorea oblongata Mart. Clwmaedorea tepejilote L iebm. Crataeva /apia L. Dendropanax arboreus (L.) Dccne. et Planch. Dus.ria mexic(//ra (Standi.) Harms Ficus insipida Willd. Guarea bijuga C. DC. Gum·ea glabra Vahl Hampea nutricia Fryxcll Lcnchocarpus crrrclllus Lundell Lonc/wcmpus guaremalensis Ben th.

Louclrocarpus stmlarosmms Donn. Sm. Ma/met1depresm (Baill.) Fries Mortoniodendron grwtcma/ense Standi. ct Stcycrm.

Omwsia istlunensis Slandl. Picranmia 0111itlesma L. PiCI'amnia terramera Turcz. Pimenra dioica L. Pithece/lobium arboreum (L.) U rban Plertrantlrodendron mexicomm1 (Gray) L.O. WilIiams

Poulseuia armata (Miq.) Standi. Psychorria spp. Pterocorp11s hayesii Hems!. Quararibeafimebtis (La Llave) Standi. Reiulumlria gracilis (H. W.) Burrett Robinsone/la miraudae G6mez-Pompa Sapiumnitidum (Monach.) Lundell Sloaueasp. Terrorchidium r·otundatum Standi. Thouinia paucidentata Radlk. Trichi/ia brevif/ora Blake et Standi. Trichi/ia tomemosa HBK. Vatairea lundellii (Standi.) Killip ex Record Vochysia hondurensis Sprague

Relicts of these selvas can be found in many other areas, but in most cases the original vegetation has been destroyed, and it is difficult to reconstruct the original selvas. Chiang (1 970) reconstructed the primary selva in the Cordoba region; he mentions the following species : Dominant species Tenninalia amazonia (Gmell.) Exell. Other species Astronium graveolens Jacq. Castilla elastica Cerv. Miconia argentea (Sw.) DC. Stemmadenia donne/1-smithii (Rose) Woods.

Tabebuia rosea (Bert.) DC. Zam!toxylum belizense Lund. Zuelania guidonia (Sw .) Brit!on et Milsp.

One of the most striking things about these communities is that they tend to form floristic units locally that can be distinguished rather easily by a person well acquainted with an area. These groupings may be used to extrapolate soil conditions

La titu de Long i tude Alt itude

18'54' 96'56' 927 OOm

Lot otude 20' 27' LOngo tude 97'19' A l to tudc 29800m

CORDOBA

PAPANTLA

DE OLAR T E

Average annual temperature 24 o•c Total annual r ain f a ll 1169.9mm

Average an nua l temperatur e 20.4°C Total an nu a l ra in to II • 2199 .1 mm

30 30

600

500

e .5c 2

'ii

5c 200

."'.\

.,~

300

.,c

;:;

400

·-·--._.·.. . . ._

20-

700

600

"r" 400

300

·a. fQ

5 200

100

" .,E"'

.I 5 100

Latitude Long itude Altitude

20' 4' 97'3' 151.00m

MART I NEZ DE LA TORRE Average annual temperature 24.0 111 C Tota l o nnu al roinfa ll 1743.4mm

A M

A Latitude Longi!ude Altitude

19"56'

96'50' 410.00m

M I SANT L A Average annu al temp erature 22.7 •c Tot al onnuol r a i nfall 2275.Qmm

700

600

500

'E .5 c

.!? 2

E' £

5c 0

.,E

.,E"'

::;:

Fig.l9. Climatographs of stations located within the region of the high semi-evergreen selvas. A. Cordoba statio n; B. Martinez de Ia Torre station; C. Papantla de Olartestation; D. Misantla station.

114

A. G6MEZ-P0 Ml'A

ECOLOGY OF Til E VEGETAT IO N OF VERACR UZ

115

TA BLE VI! QUADRAT' 1'1\0M A II lull SF-'IHVUtG it HN SELVA IN T HE CO ROO IIA REGION, G KOWING ON LIM E~.,.ON E liiLL~

Domi-

Name

IWJ/Ct:

Ficu.,· recolutensi.v

Number ofimliritlua/s

Fretj/ICIIC)'

(%)

-------r - 5

(Higuera) 2

Brm"in111111 alicMtrum

Acltras zapota

--·-~--

40.00

2,260.80

203,409.0

32.50

3,533.45

53,961.5

30.00

2,5 13.60

36,050. 5

32.50

2,575.30

26,725.5

35.00

1,570.00

26,896.5

35.00

1,570.00

19,256.0

20.00

2,421.90

11 ,1 18.0

35.00

62.80

10,1 12.0

30.00

645.50

7, 197.0

30.00

141.35

(Chicozapot e)

Cedrt:la odorata (Cedro)

Cocco/oba sp.

Croton uiteus

(Coma1illo Macho) (Vcntosidad )

Bemoullia flwnmea (Piatanillo)

9 10

Sapi11111 lateriflomm (Mameicillo) Lancltocarpus sp. (Sangre de Tore) O ther species (13)

- ------·1

( m')

Ba.ml area (em')

(Mu1ato) 4

Co l'eragc

(Ojochc)

Bursera simamba

--- ---·-

Maxi- Average mum height lteigltt ( m) ( m)

3,896.5

Achra.1· zaJwla L. Ampe/ocem lwtllei {Sta ndi.) Stand i. AspidoS{Jerma mt•galumrpun Mucll. A rg. A.stronium gra1'eolens Jacq. Bemuulliaflammea Oliver Bumlwx e/lipticum HI3K . Bunclrosia/anceolata T urcz. Bursera .liiiWmba (Sw.) Sarg. Cttpparis baducc/1 L. Cedre/a odomllt L. Cordia alliodura (Ruiz ct Pavon) Cham . Cupania dentata DC. Dioscuretlmexictma Guill. Exostema mexicamm1 A. Gray Exothea copalillo (Schlecht.) Rad lk. Ficus cuoki Standi. Ficus tecoluteusis (Licbm.) Miq. Guettardt1clliptica Sw.

llrx wndensataT urcz . lngasput'ia H UK.

Mirwulact"!tix mvnoim ( Hems!.) Sharp l\'1;-riormpa bijitrc/t Liebm. M)"roxylun bal>tlllll/111 (L.) H arms Nt•t·tandm sanguittea Rottb. l'errottctialoagistyli>·Rose Platymisfium yuC{Ifanwa Sta ndi. Protiwn copal (Schlecht. ct Cham .) Engl. Robinsonella mirattdae G omez-Pomp a Sopiwnl/llenflorum Hems!. Sickingia rlwdoclada (Stan d i.) Standi. Stcmmadenia donne/1-smit!tii (Rose) Woods. Tric!tilialtavanettsis Jacq . Tricltilia hirta L. Urera baccifcra (L.) Gaud. Vatairealt~ndellii(Sta nd l .) Killip ex Record

TAl3L E VI II QUADRAT OF A III GH SEMI-EVEKGR HN SELVA OF Brosinlltlll (1/iCII.I"Irlllll IS T HE I'OZA KICA REGION; THIS SELVA GROWS ON SOIL DE RI VED FROM CALCAREOUS 1\0 CKS

- - - - - - - - - - -·- -- --

Domintmce

Name

Number Frcofindi- quency 1•idua/s (%)

M a.ri- A rerage fteigltt mum fteigftt (111)

Co l'erage

(ni')

Basal area (em' )

(ttt)

·------

After Chiang (1970).

Brosimwn a/icastrtm1

60"

27.0

24.0

250,615.0

3,510.50

30.0

29.5

2 18,626.0

5,102.70

2 1.0

15.8

7,873.0

192.00

27.0

6,442.0

125.60

140

12.5

6.5

4,82 1.0

770.50

19.0

3,361.0

70.60

6.0

5.8

562.0

112.80

6.0

229.0

50.00

(Oj ite)

within the same area (Cuanalo and Aguilera, 1970). What cannot be done is lo extrapo late fro m one region to another (Gomez-Pompa, 1966).

Mirandaceltis monoica (Pi pin)

Castilla elastica (Hulc)

{5) High semi-erergreen selvas. This vegetation type also.a rises in humid a reas bul may be found in areas with rainfall as low as 1800 mm and with a few dry months, as may be seen in Fig. l 9. The data come from meteorological stations within the ranges of distributio n of this vegetation type. High semi-evergreen selvas may be characterized by the considerable po rtion of the tree species (up to 40 %) which have leaves deciduo us in the dry season. It is also found in areas with the &ame climate as the evergreen rain forest, but on special soil conditions , such as well-draine d rocky so ils. A good example of this last situation, presented by Chiang (1970), was found in the limestone hills of the Cordoba region where the quadra t ofTable VII was surveyed. The floristic compositio n reported for this selva is the following: Dominant species Brosimum a/icastrwn Sw.

Zuelaaia guidouia ( N ogalillo)

Guarea clliclwn (Hoja Blanca)

Pitftecellobium insigne

(Chalahuite de Espina) 7

Tabemaemolllana alba

(Coj6n de G a te) 8

lresine nigra

(13agacillo) 9 10

Alc/wmea latifolia (Pa lo Blanco) Piper aff. misantleuse (Cordoncillo Chico) Other species (45) Total

6.0

179.0

31.40

5.5

179.0

31.40

492,887.0

9,997.50

410

116

A. GOM EZ-POMPA

NAOLINCO

MISANTLA

ECOLOGY OF TH E VEGETATION OF VERACRUZ

COLIPA

Pimcuta 1/ioica L.

Pleumntlwdellllron mexiclllwm (A. Gray) L. Protium copal (Sch lecht. ct Cham.) Engl. Pithecellobium arboreum (L.) Urban Sapindus saponaria L. Sapium/ateriflomm Hcmsl.

117

Scltei•lea /iebmwmii Bccc. Sll'ietenia macrophylla King Trh-hilia hirta L. Trophis racemo.m (L.) U rban Urem caracasana(Jacq.) Griscb. Zuc/auia guido11ia (Sw .) Bri tto n c t Millsp.

Most of the soils in this region are derived fro m calcareous rocks which adds another element o f selection for the flo ra, and m a_kes it q uite uniform. This vegetation type has been considered t he northern limit of the rain fo rest in America (Rzedowsk i, 1963). I t seems that several of the species I ha t compose it are tolerant. to occasional low temperatures. This allows them to colonize some protected habitats in the extreme tropical conditions. One fact favorin g this hypothesis is that many of the species are also·fo und on t he Pacific Coa st in simila r cond ition s where they are tolerant to the extremes of t he tro pical climate. They are a lso found _in protected areas such as canyons and near river banks (Gentry, I 942, I 946) as far nor th as Sonora . Some of these species are: " 'Go;

"'G" ~tM\'IYI~•tlro

~( ,. q¥ (1(;1(( N

M0NfA.Nl ~(IY4

~h ....

O u :; tOf l\f

Fig.20. Vegetation pro fil e in centnil Veracruz (Naolinco-Colipa) on the Sierra of Chiconquiaco.

A very similar gro up o f species has been reported from limestone hills in Oaxaca (Gomez-Pompa et al. , 1964b). Apparently the limestone and rapid drainage combine to have a highly selective action on the available species. This vegetation type could have been fo und in alrthe lowland areas with welldrained soils, from the Misantla region up to Tuxpan and even north of T uxpan along the river banks. M ost of these selvas have been d estroyed by man but there are a great number o f patches remaining that give a fairly good id ea of their original structure (Table VIII ; Fig.20). Among the species known from these selvas, the fo llowing are characteristic: Dominant species Brosimum alicaslrllm Sw. 0 I her species Achras zapata L. Bumclia persimilis H emsl. Bw·sera simamba (Sw.) Sarg. Carpodiptera ameliae Lund. Castilla elastica Cerv. Ceibapentandra (L.) G aertn. Chamaedorea lunata Licbm. Ch/orophora tit1ctoria (L.) Gaud. Cupania denlata DC. Dendropanax arboreus (L.) D ecnc. et Planch.

Diospyros digyna Jacq. Enallagma lat1/olia (Mill.) Sma ll Ficus iusipida Willd . Guazuma ulmifolia Lam. Iiemaudia sonora L. Mastichodendron capiri (A. D C.) Cron. var. tempisque (Pitt.) Cron. Mirandace/tis monoica (Hems I.} Sharp Misanteca capita/a Cham. ct Schlech t. Phoebe mexicana M eissn.

Brosimum alicastmm Sw. Urera carac(lsana (Jacq.) Griscb. Chloroplwra tinctoria (L.} Gau d.

Guozuma u/mifo/ia Lam. Sapindus saponoria L. Trichilia hirta L Trophis racemosa (L.) U rb.

These selvas of the extreme northern tropics may have occu pied a much wider distribution in the colder geological past, and the commu nities that today seem to be disjunct were part of the same genetic stock. Very interesting experiments may be designed to evaluate the degree of population differentiation in some of the common species from the Pacific and Gu lf coasts. Th is is especially interesting, because it seems that the species of the Pacific have a wider soil tolera nce than those of the Gulf. A n example of this is Brosimum a/icastrum that grows in different substrata in N ueva Galicia (Rzedowski and McVaugh, 1966) and is not restricted t o limest~ne s as it is in northern Veracruz and San Luis Potosi. I n the lower part of the mountains in very wet regions, the Liquidambar fores ts and the lowland high selvas come in contact, and a different and very interesti ng semi-evergreen selva develops, with flo ri stic elements from both sides. This is a very tall vegetation that may reach more than 40 m in height. This selva is not well known and d escriptions are scarce. The mixture of high humid ity and moderate low temperatures creates a unique etlVironmen t, and many genera and species are known in Veracruz only fr om such selvas. Because of t he abundance of species of the fam ily Lauraceae, it has been called Selva of Lauraceae (Gomez-Pompa; 1966), and it is shown in the profile in Fig.20,2l as high montane semi-evergreen selva. Some of the species known fro m this kind of selva are: Alchomea latifo/ia Sw. Beilschmiedia anay (Blake) Kosterm. Beilschmiedia mexicatla (Mez.) Kosterm. Calato/a laevigata Standi. Ceratozamia mexicana Dron gn.

Nephelea mexicana (Sc hlech t. et Cham.) Tryon Dalea e/ata Hook. et Arn. Dussia mexicana (Standi.) H arms Ficus lapathifolia (Liebm.) Miq. Hampea integerrima Schlecht.

118

A. G6 M EZ-I'O MI'A

Licaria !IC:Ckii (Johns!.) Kostcnu. Miconia rrincn•ia (Sw.) Don Mirmulacelri:l" moJIOfca ( Hems!.) Sharp Nec/mulm salicijiJ/ia 1-1 B K. Ocoretl ••eraguensi.1· (Mcissn.) Mcz Pe1·5ea schiedeaJUt Nccs

!'ilea pube.1cens Licbm. Piper sancl/1111 (Miq .) Schlecht. J'ou/senia armaltt (Miq .) Standi.

Que.r.c.J.Js t:tuTuJ:ala I look.

Q11Crcu.1· aiL 11racili11r Mull . Quen·u.1· .l"kinneri !lentiL Saurauialaevigata Trian;1 cl Planch.

Sp/wemplc'ris hurricla (Licbm.) Tryon Tapiriram(•xicmw M Hrchand

Trimeztlnl/lrlinicemis (Jacq.) Herb. Virola guotemaleusis (Hconsl.) Warb. Ulmus mexil'illlfl Licbm.

VOLCANO OF SAN MARTIN, LOS TUXTLAS , VER.

1500

soo-·- --

LIOUIOIIMBAR FOREST

ECOLOGY OFTI·I E VEGETATIO N OF VERAC RUZ

119

munity is dete r mined by such factors a s : water availability, strong winds, and soils. It is probable thai other facto rs incl ud ing a nimals and fi re may also play an impo rtant role. Because of this, the trigger factor may not always be the same. The fl oristic composition of this grou p may a lso vary greatly.

(7) Low el'ergreen selra. T his type of selva is found in a very restricted locality at the top of the volcano of San Martin (Fig.2J ), and probably grows on Santa Marla as well. It is a small, very dense· forest wit h many epiphytes, mosses, and lichens, from which another name fo r this vegetation, "mossy forest", is derived . It is. also known by the na me "cHin fo rest" o r "elfin wood land". These selvas pose an important problem because, even though they grow in a very humid habitat with good deep soils and abundant light that could prod uce a tall forest o r selva, they produce this low selva. There have been several important studies made in Puert o R ico on a similar vegetation type (Howard et at., 1968), but until now without a definite solu tion. For a long time wind has been considered the explanation for t his se lva, but t here is no evidence avai lable that t his is true ( Bayn ton, 1968). However, the q uestion remains open, if periodic cyclon ic disturbances , not necessarily record ed, struck the tops of these mou ntains mo re strongly than the adjacent lands- one strong wind every 20 yearswould this be enough to keep the selva short. In our region in Veracruz, -ihis seems clearly to be the case, as mentioned by Sousa (1968) in his observations after a cyclonic d istu r bance struck the a rea. Another ecological factor not considered normally is the low light intensity throughout the year in this type. Genecological studies seem to be needed to help solve the problem. The only locality known in Veracruz for this vegetation type is the top of the San Martin volcano; from this area Sousa (1968) mentions the follow ing species:

40~~

Clusia salt•inii Donn. Smith £1/eautlws capiratus (P. et E.) Reichcnb. f. Gaultheria nit ida Bent h. llcxsp. Lirseasp. Mouninasp. Myrica cerifera L.

In this group a heterogeneous a rray of vegetatio n types occur~. The . height of t l1e types to be considered here do not exceed an average of 10m. The stature of any com-

(8) LoiV semi-el'ergreen selvas. In drier a reas (ca. 1,400-!,800 mm rainfall), or in more humid areas with poor soils and with drainage problems, these selvas can be found (Fig.22). They are very large in extent because many of them give very poor agricultural yields and are used o nly fo r certain crops, such as pineapple and some grasses that can maintain only a few cattle. In some of these areas there is a strong suspicion that t his vegetation type may be of secondary o rigin, bu t t here is not sufficient evidence. T his type is strongly related to the tropical lowland oak forest and to the savannas, and varieties of it are often f ound together forming a complex mixture of types called "selvas sabaneras". Floristically they are also closely related to these, and it seems that in several cases one type ca n give rise to the other, given certain human practice& (slash-burn agriculture).

Fig.2 1. Vegetation profile oft he San Martin volcano (Los Tuxtlas).

{6) Medium semi-evergreen selras. T his vegetation type is about 15-25 m tall. Up lo

or more of its species have deciduous leaves. [t grows in different climates but is found mainly in drier areas than the p receding types (in places with 1,400 mm or more rainfa ll and with a · pro nounced dry season). They are also found very frequently in drier areas but along the river banks. Tt is d ifficult to characterize t his type of selva flo ristically because it is intermediate , being composed of the drier tolerant species of the ta ll selva~, the more humid represen tatives of the low selvas, in addition to a few species of its own.

Low seh>as

Orcopanax xalapense (H BK.) Decnc. et l'lanch . Policourea galeolriana Marl. Rapauea jurgemenii Mez Saw·auia villosa D C. Senecio arborescens Stcetz Vibumummonranum Lundell

rA--·---------------------Lot• tude Longitude Altitude RODRIGUEZ

19'39" 95°25' 148m

ECOLOGY OF THE V EGETATION OF VERACRUZ

CLARA

Average annual temperature 26.3°C Total annual rainfall 14353 mm 30

E "c

·-·"'.--·--.....

~ E

"·\

700

··-

Ave rage annual t ern perature 25.6°C Total annual rointoll 1401.5 mm

6oo"E

500

~ :;:;

4QO

.'l

8E "'"'~ ">

a 300 10 r--

:hr; ..

......r·

~-.~.-~ . -:::~:.•-:;p:-1 . -. •..., •.., , J

200

F M A M J

,~,,i.

j·

600

500

.'::

400

2 "ii

300

~ a

..g

200

N D O

B Latitude Longitude Altitude

"E E c ·;;

""'c ">

100

r:~·

. 1: :l

A S 0

700

:liJ-q_

I :

: ' ' ' /i'm l,il!

3"'c 0

p;;;

·•

L otitude 2o•n· Longi t ude_ 96'46' A l titude 8.00m

NA U T L A

.........

121

100

17'47' 95°11' 39.00m

JASOND BE L LACO

Average annual temperature . 25.7°C Total annual r ain fall 15B5.2mm

A few of the tree species may be deciduous, but most are evergreen. This vegetat ion type is also very widespread in other tropical regions of Mexico a nd in tropical America under differe nt names; it is designated as a special type of savanna or savanna-like vegetation (savanna woodland, cerrado, selva sabanera) a nd in most cases there is no explanation for its occurrence. T his problem also remains open. The follo wing species are characteristic :

E "c

"a E

c ·;; 0

.'::

Acrocomia mexicana Karw. Byrsonima crassifolia (L.) DC. Curatella americana L.

Psidium guajava L . Crescentia cujete L. Coccoloba barbadensis Jacq.

·;;

, :c a

""'c

Fig.22. Climatograph of a station in the region of the low semi-evergreen selvas. A. Rodriguez Clara station; B. Bellaeo station; C. Nautlastation.

(9) Low deciduous selvas. In the dry warm lowlands this vegetation type seems to be the most widely established one. It is found in regions with Jess than 1,500 mm precipitation and with a pronounced dry season that may last more than six months (Fig.23). It may be up to I 0 m taU but is usually shorter. During the dry season most of the trees remain leafless and very few plants remain active (Janzen, 1970; Fig.24). The structure of the selva sampled n ear Puente Nacional can be seen in Fig.25. This community grows in soils that are derived from limestone and are of dark color, but the same vegetation type is found on other substrata.

Latitude Long1tude Altitude SOLEDAD

19 ' 3· 96'25'

ECOLOGY OF TH E VEGETATION OF VERACRUZ

77m

123

DE DOBLADO

Average annua l tern perature .25.4 oc Total annual r ainfall 943.8mm

700

600 5 c 0

500

!l (l

400

" L

.."'

300

~ >

200

:?.> L

c 0 ::;:

5 100 0

lvl

N 0

Latitude Longitude Altitude

1 8 ' 53' 96'17' 1B00m

CAPULIN ES Average annual temperature 25.8'C Total annual rainfall 1366.1 mm

700

2 ~

" E

.§

·z

.?-

;;

·o.

Fig.24. The low deciduous selvas have a great number of xerophytic plants, such as Acanthocereus , Agave, Nopalea that can be seen in this photo.

The floristic composition of these selvas is quite different from that of other vegetation types. The following species are characteristic:

·;:;

Dominant species

!?"'

:?.>

;;

" >

::;:

Cordia dodecandra D C. Crescentia alata HBK. Emerolobium cyclocarpum (Jacq.) Griseb.

Piscidia piscipula (L.) Sarg. Tabebuia chrysant!Ja (Jacq.) Nicholson Tabebuia rosea (Bert.) DC. Other species

Fig.23. Climatograph of a station in the region of the low deciduous selvas. A. Soledad de D oblado station; B. Capulines sta tion.

Acacia comigera (L.) Willd. Acaciafarnesiana (L.) Willd. Acanthocereus pentagonus (L.) Britton et Rose Aeschynomene compacta Rose

Agavesp. Bunchosia bioce/lata Schlecht. Bromelia pinguin L. Bw·sera bipinnata Engl.

I 124

Loti tu de

22'14' 9 7"51 ' 12.00m

Long it ude Alti t ud e?

A. G6MEZ-I'OMPA

T AM P I C 0 , TAM P 5.

JALAPA~VERACRUZ

Avcr·a~e

an nual tem pera ture 2 4 .3'C Tot al onnuol rain f all 1079.9 mm

/·-·-·,.

~ ~ ~

l:> ~

,.,

"·\

/./

700

500

E .§

500

c 0 ·.;:;

:;:

400

" ~

2' 300

01 0

200

::t:

5 100 llQ UIOAM8MI· OAK f0R£SI

GRASSLAND

lOW DECIDUOUS SElVA

COASfAL V (GUATION

0 F

Fig. 25. Vegetation profile of the region between Ja lapa and Vcra~ruz City.

Bm·sera }itgaroides (H BK.) Engl. Bursera simamba (Sw.) Sarg. Byrsouima crassifolia (L.) DC . Casearia nitida (L.) Jacq. ·celtis iguanaea (Jacq.) Sarg. Cltloroplwra tiuctoria (L.) Gaud. Citlwrexylum ellipticnm Sesse et M oe. Comoc/adia engleriana Loes. -cordia pring/ei Robinson Coutarea hexaudra (Jacq.) Schum. Cratael'a /apia L. Croto11 g/andrtfosepalus Millsp. Croton puncta/us Jacq . Cupania macrophyl/a A. Rich. Cumtella americana L. Dalbergia g/abra (M ill.) Standi. Dap/mopsis brevijo/ia Nevi. Dioon edule Lind!. Erythroxylon m·eo/atum L. Eugenia liebmannii Standi. Ficus cotinifo/ia HBK. Ficus maxima P. Mill. Ficus obtusifo/ia HBK. Guettarda elliptica Sw. Haematoxylum brasi/etto Ka rst.

Hamelia patens Jacq. Jatrophapseudocurcas Muell. Arg. Luehea speciosa Will d. Mabavem e-cmcis Standi. Nopalea dejecta Salm-Dyck Okeuia hypogaea Schlecht. ct Cham. Opulllia pubemla Pfeiff. Parmentiera edulis DC. Phyllantlws grandifo/ius L. Phyllam/ws nobilis (L. .f) M uell. Arg. Pithecellobim11 calostachys Standi. Pithecellobium erythrocarpum Standi. Plumeria acutifolic! Poir. Randia acufeata L. Ran(/ia albonervia Brandeg. Sabalmexicana Mart. Sageretia efegans (HBK.) Brongn. Salvia coccinea J uss. Sapium sp. Tamonea curassavica Pers. Tlrouinidium decandrum (H. et B.) Radlk. Trichi/ia havanensis Jacq. Trichilia parvifo/ia C. DC. Zanthoxylumfagara (L.) Sarg. Zuelania guidonia (Sw.) Britton ct Millsp.

2 2 ' 3' 99'11' 22.00m

Lotitcde Longitude A ltitude PANUCO

Average OI1Tlual tempera tu re 23.8'C Total an nual rainf a ll 915.5mm

. . . . -·--·-·

;·

E ~

.::

l" ~

E ~

,.,

"·

'-..._

"""·

E .§ c 0

.8 Cl ·v

"....

c 0

::;:

{10) Low thorn seh·as. This vegetation type is found in the driest regions oflowland areas where precipitation is under 1,000 mm and where the dry season is long and Fig.26. Climatographs of stations in the region of the low thorn selvas in northern Veracruz. A. Tampico station; B. Panuco statio n.

126

1\. G6MEZ-I 'OM PA

ECOLOGY OF TilE VEGETATION OF VERACRU Z

127

pronounced (Fig.26). T hese regions a lso have the lowest winter temperatu res in the lowlands. The co mbined efrcct o f these highly select ive litctors gives rise to the very character istic flora, which is a combination of floristic clements from the more h umid a reas in the sout h and the Tamaulip as desert s in the north. T he soi ls of th is northern area are very dark in color and a rc clayey, b ut otherwise no t well known. Among the species fo und r mention the following that arc fl o ristically characteristic of this vegetatio n type: Abulilon /rique/rum A. Rich. Acacia collstricta Dent h. Acacia lcxew;is T. ct G. Aclw /ocw1111S 11ig ricans Triana Boerlwl'iu erec/a L. Cordia alba (J acq.) Rocm . ct Schult. Cordia boissieri DC. Coursetia axil/uris Coull. ct Rose Cltloropltom tincloria (L.) Gaud. Cillwrexyltmt berlmulieri Robins. Cro/OnnilemÂˇ Sw. Erylltroxyloll areolatwn L. Eugenia licblltattttii Standi. Guazuttw tdmifo/ia Lam.

Jacqui11i11 axil/oris Ocr st. MalfJigftia flllllicifo/ia L. Mimosapigm L. Morrisonio ttmericano L . Nopalea cocltenil/ifcra (L.) Salm-Dyck Parkimonia aculcula L. Pltyllallllws micrandms Mucll. Arg. Plumbago sp. Pilltecel/obiwll sp. Randiasp. Solannmlanceifolitmt Jacq. Scltoepjia scltreberi Gmel. Tric!tilia parl'i/olia C. DC. Zyzyp!tussottorettsisS . Wats.

(I 1) Palm slands. This vegetation type is rat her widesp read in the humid and subhu mid lowlands, where two principal kinds may be distinguis hed: the Schee/ea palm stands and the Saba/ palm stands. Physiognomically these may be distinguis hed easily by t he pinnate leaves of the fi rst gen us and the fan-shape d leaves of the second. The Scheelea /iebmmmii palm stands have been considered an anthropo genic vegetatio n type, since th is plant is protected and conserved during the usual destruction of the vegetatio n as it is used for many purposes, such as ho use construct ion, firewood, and food. As this palm is a principal compone nt of other vegetatio n types such as the tall evergreen, the semi-evergreen and the medium semi-evergreen selvas, the destructio n of such selvas favors the spread of this palm, which forms dense secondary communi ties d iflicult for any other trees to compete. Even thoug h most of the palm stands in t he state are of this origin, there are several places in which this palm is domi nant, where no direct evidence links the palm stands with luunan activities. These- primary palm stands are fo und in soils that are inundated during a large part of the rainy season (Fig.27); they are composed floristically of many species with similar ecology. Some of the t ree species that character ize this type of vegetatio n are: Albizzia purpusii Br. et Rose Bunchosia lanceo/ata Turcz. Cit!tarexylum hexangulare Greenm. Cupania dentala DC. Pleurantltodendron mexicanum (A. G ray) L.

Sapi11dus saponaria L. Sclteelea liebmanii Becc. Stemmadenia galeolliana (A. Rich.) Miers Tropltis racemosa (L.) U rban

T he other palm stands, d ominated by Saba! mexicana, is a controversial one. It grows in drier areas with a d rastic dry season, on fiat clayey soils (planosol s) along the coast.

Fig.27. The palm stands of Sc!tee/ea liebmattnii a re very abundant in soils that have a high water table, like this one in the region of Tesechoacan.

f n these area~ fire s are very common during the dry season, and it seems that the presence of this palm is favored by fi re {Fig.28). On the other hand, there a re a reas where the palm is dominant and fi1e seem s no t to be as importan t. Addition al work should be d o ne in the field to learn more about the role of fi re on t his vegetatio n type. A quadrat made on one Saba/ stand may b e used as an example (Table IX). Another palm stand of red uced area is the one composed by PawÂˇotis wrightii in the swamps of southern Veracruz. This p alm is also fo und in savannas, but only in soils where t he water table is high and is above the surface for part of the year (Fig.29). Many of the species growing in palm swamps are found also in inland swamps and will be discussed later.

128

A. G6MEZ-POMI>A ECOLOGY OF T HE VEGETATION OF VERACRUZ

129

T A BLE fX

- ---

Daminance

1 QIJADitAT IN A SAllAL I'AU.I STAND IN TliE RL'GION OF COSMIAI.OAI'IIN

Name

Pilhefellobiwn/anceo/atum

Numbet· o[iudi1•iduals

665

Frelflll!IIC)'

(%) 100

Maxi- A1·cragc mum height (m) height (m}

Col't!rage

Basal area

(m>)

(em')

1 1,7~6.5

5.7

10.0

3,221.0

62.5

(G uamuchil)

Sahalmexinma (1\pachilc)

Zantlwxylunt caribaetmt Ruprechtia coswla

5 30

6.0 6.0

2,248.0 1,490.0

26.5 553.5

6.0

8 14 .0

125.0

Randiaacnleata

4.8

337.0

13.5

(Crucctillo) Acacia cornigera (Cornezuclo)

7 .5

338.0

252.5

(Lagunillo)

Pit!tecel/ol!iwn recordii (Amczquilc)

T otal

750

12,770.0

- ------·--• After Gomez-Pompa et al. (1964b).

Fig.28. The Saba/ mexicana palm stands are abundan t along the coast on flat and clayish soils in climates with a pronounced dry season.

Grasslands There are three main different vegetation types included in this term. They have a very &imilar physiognomy as herbaceous Gramineae are dominant. The first type is the lowland tropical grassland, better known as savanna; the second is the grassland of temperate climates; and the third is the saline grassland. In other localities in Mexico there is an additional type occurring in cool areas in the mountains. This has not been reported yet from Veracruz.

( 12) Savannas. The term savanna (also sabaria, savannah, savana) has been used as a name for a great number of rather different vegetation types. I will use it only for the

Fig.29. The Paw-otis wrightii pahii stands are closely related to the savannas (on the more humid soils) and also to the swamps (on the drier soils).

130

A. GOMEZ· I'OMI'A

ECOLOG Y OF THE VEG ETATION OF VERACRUZ

tro pical lowland grass lands, with or without scallered trees (Fig.30), growing on special soils with drai nage problems a nd, usually, with a aclinitc clay layer. T he savanna s or Veracruz are very much like the cdaphic savannas describe d by Beard (1953) ror tropical America and by Go mez-Pompa (1965) ror Mexico. The proble m with savanna s is that in many cases, especially in regio ns with a pronoun ced dry season, period ic fires may change t he physiognomy or the vegetatio n in the area to a savanna-li ke physiognomy. Several species o r savanna s are preadapted to fire survival and can exploit the resulting new niches. lt is very clear that in such cases soil is not the basic raclor and an anthropogenic o rigin may be suggested. I n other words, a more detailed study should be made to determin e whether certai n

13 1

SABANA COSTERA,COATZACOALCOS

SAVANNA

PAUROTIS PALM STAND

REO LATERITIC SOILS

SAVANNA

ALLU V IAL SOILS

LAS CHOAPAS, VER.

F ig.30. A savanna in southern Veracrul; the tree is Curatel/a americana

areas are true savannas or only have savanna-like seconda ry vegetatio n (GomezPompa, I965). · The savannas are closely related to the tropical oak forests a nd are frequent ly found to share many species. This relations hip depends on the soil types ; the savanna grows on poorer soil than do the oak forests. The savanna s of southeas tern Veracruz have been studied by Leon C. and GomezPompa (1970). Two profiles with savanna s and their adjacent selvas may be seen in F ig.31. Other species from t hese savannas are the following: Paspa/um pectinatum Nees Acisanthera quadrata J uss.

Acrocomia mexicana Karw. ex Mart. Ageratum sp.

SAVANNA

HIG H EVERGREEN FOREST •

SAVANN A

Fig.3 1. Vegetation profi les of a region in southern Veracruz showing the soil differences due to topography between a selva a nd a savanna. A. Sabana Costera, Coatzaco alcos; B. Las Choapas, Veracruz.

Andropogon altus Hitch. Andropogon bicomis L. Bulbostylis afT. paradoxa Nees Byrsonima crassifolia (L.) DC.

Cassia diphyl/a L. Cltamaesyce hyssopi[olia (L.) Small Coccocypse/um sp. Cologania sp.

132

A. G6MEZ-PO MPA

Cmro;-tegia 1>11t:ciosa Naud . Crotalaria sa.t:itta/is L. Cumtelfa llmcricaua L. Diclwomcua ci/iaw Valli Diodia rig ida C ham. et Schlee hi. Elcoclwri!; intcrstiuc/a (Vahl) R. ct S. Fuirenasp. Hibiscus co.!"lllllls Rich. flyplis confer/a Po hl. Hyplisafl'. rugosa L. Kylliuga brwifolia Roub. Me/ochia hirsllla Cav. Mimosa pudica L. Myrica ceri[era L. 0/yra /ali/alia L.

Paurmis wl"if!/llii (Griscb. ct Wend I.) Brit!. Po/ygala aff. adcnop/wra DC. Poln:ala spp. Psidium guajma L. Psidiwumolle llertol. Rhynchalllhcra mexicaua DC. Rhynclwspora all". barbala (Vahl) Kunth Rhynchospora an·. lougispicata 13occckle. Russe/iafloribunda HBK. Saul'agesia erccta L. Setaria geuh·u!tita (Lam.) Bcauv. Spermacocc lwcuckeana Hcmsl. Xyris ambigua lkyr. Zcxmeuia aarea l3enth .

ECO LOGY OF TH E VEG ETATION OF VERACRUZ

, -- -- - - - - -·-Lati tude Longo tude

Att itude P E RO TE

Anthericwn aff.leucocomum R ob. et Grcenm. Anthericumuanum lla ker Asclepias glaucesceus H BK. Asclepias rosea HIJK. Bulbostylis capillaris (L.) C. B. Clarke Cologauia procumbeus Kunth Commeliua dijfusa Burm. f. Cyperus seslerioides HBK. Eryngium carliuae Detar. Heliatropium/ruticosum L. Ipomoea muricata Cav. Microchloa kuulhii Desv.

Nemastylis tenuis (Herb.) Baker Ophioglossum sp. Oxalissp. Piranopappus roseus Less. Quercus peduucularis Nee Rammculus hookeri Schlecht. Selaginel/a sp. Setaria genicula/a (Lam.) Beauv. Sisyrinchium sp. Stevia elarior HBK. Tridax procumbens L. Verbena teucrifolia Mart. et Gal.

The area in which I thin k this vegetation type was more extensive is the Valley of Perote, which has been used for agriculture for a long time. The rainfall here is low enough to cause problems for almost any tree community but is above the upper limit of a typical desert (Fig. 32). Unfortuna tely, today we can find only weeds in all this valley; but two grasses growing in the vicinity give us a clue: Boute/oua curtipeudula (Michx.) Torr.

Bouteloua gracilis (HBK.) Lag. ex Steud.

( 14) Saline grasslands. An edaphic grassland in a temperate region near Alchichica has recently been discovered. It is the only upland saline communit y known in Veracruz. T his grassland occupies a small area in the valley near Alchichica in the states of Puebla and Veracruz. It is a closed deep valley which becomes a small lake or swamp in the rainy season. In the dry season it is completely dry and very saline because of the evaporatio n of water (Fig.33).

700

.. c

25 600

3 Cl

is very poorly represented in Veracruz, if at all. Some areas in the transitional boundary between temperate subh umid to temperate dry climates are covered by a nat ural grassland, although their range is rather limited. The following species have beerr found in one of these grasslands above Orizaba on the lower ~l opes of the Cuesta de Maltrata:

- -...,

19'3 4 ' 97'1 4' 2465.00m

Average annual temperoture 12. 7•c Tot al annual rai nfa ll 525.2mm

..~

( 13) Temperate grasslands. This type of grassland is found in temperate climates but

133

5 00

~ > <{

/·-·-·- ·-· .1 '"'·--.........___,

3 v

400 c

........

c 0 :;

·c.

:5c

'E .5

5"'

300 c

0 }:

200

5 100

A MJJA

Fig.32. Climatograp h of a station located in an area that probably was occupied by a t emperate grassland.

The following species have been found in th is saline grassland: Distich/is spica/a L. Actiuel/a cl11ysanthemoides HBK. Altemauthera repens (L.) Kuntze Aphanostephauus lmmilis (Benth.) A. Gray Astragalus wootoni Sheldon Atriplex pueblensis Standi. Boute/oua breviseta Vasey Croton dioicus Cav. Cuscuta saliua E ngelm. Dichondra argentea Willd.

Erodium cicutimu11 L'Hcr. Gomphrena dispersa Standi. He/iotropium curassavicum L. Hous/onia rubra Cav. Pla!llago niveo Kunth Sanvitalia procumbeus Lam. Scleropogou brevifo/ius Phil. Stipa editoram Fourn. Verbena cauesceus HBK. Verbena cilia/a Benth.

Another edaphic grassland (Fig.34) reported from Veracruz (Vazquez,. 1971) is the Spartina grassland ("espartal") in the coastal region, in Mandinga. These grasslands are inundated periodically, and as a result their soils are very saline. The followin g species have been reported from them: Andropogon g/omeratas (Walt.) BSP. Balis maritima L. Borrichia/ratescens (L.) DC. Fimbristylis castanea (Michx.) Vahl

Fimbristylis spathacea Roth Sa/icornia pel'elmis Mill. Sparliua alterniftora Loisel. Spartina spartinae (frin.) Merr.

134

/\. G6MEZ- 1'0MPI\

ECOLOG Y OF THE VEG ETATION OF VERACR UZ

135

Arid or semi-ari d rege/alion

It is quite d iftlcult to g ive a good definitio n o f ar idi ty that will be satisfacto ry both from the point of view of the vegetat ion a nd of the climate. I am well aware of the problem of u si ng a vag ue cl imatic term in vegetat ion classifica tion but its use seems justifiab le in this case, because of the s harp climatic del imitation of t)1ese vegetatio n types. Such commun ities are very poorly represen ted in the state, and in most ca se~ have been ignored. They arc not represen ted on most general climatic maps, often because there are no meteoro[ogical stat ion s in the areas, so that extrapolation based on vegetatio n is necessary for characte rization.

(15) Nolina-Hechtia-Agat•e desert. T his type of deser t which grows on some of the limestone h ills west ·of Perote, on the border with the state of Puebla, has recently been st ud ied by Ramos (197 1). The climate of the area is very dry (Fig.35), probab ly the driest in Veracru z. The data from the town of Alchich ica on ly a few miles away in the state o f P ueb la may be used for this area. This vegetatio n has been called by Fig.33. T he only halophytic grassland found in the stale grows at the border of the sta tes of Puebla and Veracruz ncar Perote; Distich/is spica/a is the dominant species.

La t itude Longitude Al t i t u de

19'15" 97'32' 23.50m

ZACATE PEC, PUE.

Average onnuol temp erature 14 goc Total annual ra infall 360.8mm

l1 ~

0L ~

~ c

E ~

"'0 L

F ig.34. A halo phytic grassland ("csparta l") near the coast of Veracruz. This grassland is inundated d uring the rainy season for several months. (After Vazquez, 1971.)

c 0 ·;;

500

4 00 "(i

-·o ~

c. ~ r: ~

0 ~

136

A. G6MEZ-l'OM I'A

ECOLOGY O F T HE VEGETATIO N O F VERACRUZ

Lrmrus pldcoidcs H BK . !l'fumillaria dcalbata Brill . ct Rose Mamillaria elcgans Bri tt. ct Rose Salvia cane>·cens llcnth.

137

Sal••ia coultct1 Fernald Sah•ia t ftymoide.\' Bent h. Stipa teuuis.1·imaTrin. Tmde.vcautia brachypllylla G rcenm.

( 16) Thom scrub. T his vegeta tional type is composed ma inly of shrubs less tha n 3m tall, most of them spiny. T here a re two mai n clima tic groups in the thorn scrub : one in high altitudes (1 ,500 m or more) a nd the other of lowland s (less than 500 m ). The main difference is not in the ph ysiognomy but in the fl oristic compositio n, although a se ries of common species is shared . The scrub from the highlands is found in very small patches in the dry area s near the forests of semi-humid temperate climates. T he only considerable area known to have this type vegetation is in the region of Santiago, Veracruz, on the border with the state o f Hidalgo. Many large cacti al so form part of t he vegetation. The fo llowing species may be mentioned : Agal'esp p. Asclepias linaria Cav. Bo111•ardia longif/ora H 13K. /Judd/cia an·. skutchii Morto n Croton ciliato-glandu/osus Ortega Echinocactus sp. £upatoriwu espiuosamm Gray Junipems.afl'./faccida Schlecht.

Fig.36. The Nolina-Hechtia-Agave desert grows on limestone hills, and often Junipcms is an important element in t he community.

various na mes deri ved fro m the rosette-like arrangement of the leaves : "matorral rosetofilo" a nd "matorral rosetu lifolio". This community h a~ flori stic affinities with the flora of the deserts of central Mexico, sha ring many taxa with the "zona arida hidalguense" and the " zona arida poblana" (Miranda, 1955). The physiognomically domina nt species may vary in different micro-habita ts of the area, but grow together in most cases (Fig.36). The fo llowing species characterize this desert: Dominant species · Agave obscura Schiede Hechtia roseana L.

No/ina parvif/ora (H BK.) HemsI. Other species

Adolph/a infesta HBK. Aneilema karwinskyana (Roem. et Schull.) Wood s.

At·istida barbata F ourn. Aristida glauco (Nees) Walp. Chrysactinla mexicana A. Gray

Bouvardia scabrida Mart. et Gal. Dalea me/antha Schauer Dasylirion acrotriche (Schiede) Zucc. Dyssodia setif/ora (Lag.) Robbins Loeselia glandulosa (Cav.) Don

Km·ll'insk ia humboldt irma (Rocm. c l Schult.) Zucc. Mammillaria celciana Lcm. Mammillaria camptotriclw Dams Myrtil/ucactus geomctrizans (Mart.) Console Notho/aena sinuata (Lag. et Sw .) Kaulf. Opullliasp. Quercus eduanli Trc).

The lowland thorn scrub occurs more abundantly in the northern part o f the state on the border with Tamaulipas. Here, a mixture of this vegetation type and the low thorn selvas generally occurs. In man y cases the thorn scrub appears to be only a secondary stage of the low selvas that have been kept low by an unknown factor (herbivorou s animals?). Up to now I have fo und no other explanation fo r its presence and have included it here because more study is needed to determine whether it should be combined with the low thorn selvas. The following species have been reported in this type : -Bursem simar~~ba (Sw.) Sarg. Capparis incana HBK. Capraria bif/ora L. Condalia mirandana M .C. Johns!. Esenbeckia berlandieri BailI. Karwinskia humboldtiaua (Roem. et Schult.) Zucc.

Nopaleasp. Prosopisjuliflora (Torr.) Cockerell Pithccellobium/fexicau/e (Benth.) Coult. Ra11diasp. Yucca ·trecu/eaua Carr. Zallthoxylumf agara (L.) Sarg.

(17) Swamp vegetation. There are two main types of vegetation in the swamp s : the inland fresh-water swamps and the mangrove swamps that have marine water coming into them. Both types are found in the lowland areas o f the state. (18) Inland swamps. These swamps are f ound in m any scattered areas in Veracruz. Very little is known of their ecology or their floristic composition. The only inland swamps already described are the ones in the sou thern part of the state (Miranda and

A. G6MEZ -POMP A ECOLO GY OF T il E VEGET ATION OF VERAC RUZ

Hcrnitndcz X., 1963 ; Leon C. and Gomez-Pompa, 1970). The soils or these swamps arc inundated the whole year except on their outer border s where they may be free of water for some mont hs in the dry scaso11. Locally these communities have names connected with the local name of the domina nt genus. For exa mple, the Thalia swamps arc called "popales" (Thalia = "popoay"). The species that characterize these swamps arc: Bactri.1· colwue Watts. Cypems J:igm/leus Vahl Cypemsspp.

Eleocharis iuterstiucta (Vahl) R. ct S. Poutederia .mgitafla Pres! Thalia geuiculata L.

The physiognomy of these swamps is derived from the most abundant species and therefo re varies locally.

( 19) Ma11grove swamps. These swamps develop in the coastal lagoons of Veracruz and along many of the rivers (Fig.37). There arc several general reports on the mangrove swamp s of the Veracr uz coast, but the only complete study is the one made by Vazque z (1971) in the Mandi nga lagoon a few miles south of the Port of Veracruz. From this study we get a good picture of the diversity of such swamps in the state. The zonation of the mangrove swamps in Mandinga is very complex because of a

139

combination of ractors , but it follows c~rtain pred ictable patterns. Rhizop!Iora is found most frequently on the exterior border where the wate r level is higher (up to 50 em in Mandinga) nnd where the soils are softer. In n\ore solid soils and sha llower wntcrs A ricennia beco mes predominant, formin g dense comm unities. Mi xed with this mnngrove, Lagwrcularia is fou nd, which becomes very a bundan l in disturbed areas. Conocarpus has not yet been found in Mandinga, but it is known from other swamps in Veracruz. . The roll owing species have been reported from mangrove swamp s in Veracr uz: A••iceuuia germinaus L. Couocarpns erect us L.

Lagunc11/arirt raccmosa {L.} Gacrtn. f. Rhizoplwra mangle L.

Closely_related to the mangrove swamps are o ther swamp forests in Veracruz m areas having a very small amount of saline water (Vazquez, 1971). These are characterized by several species that can live in inundated soils but are more typical of in land types living together with typical aquatic species. The fo llowing species have been reported (Vazquez, 1971) from a swamp of this type; Dominant species Pachira aq11atica Aubl. Other species Acrosticluml aureum L. Amerimt/011 browuii Jacq. Annona glabra L. Avicemtia germi11a11s L. Clerodeudrumligustritlltlll (Jacq.) R. Brown Da/bergia ecastophyllum (L.) Taub. Diospyros digyna Jacq. Ficus iusipida Willd. Hibiscus tiliacetts L.

Laguncularia racemosa (L.) Gacrtn. f. Pithecellobitml dijdfem m Lundell Pithccellobiwu erythrocarpum Standi. Piper uitid11111 Vahl Raudia aculeato L. R/wbdodettia bif/ora (Jacq.J Mucll. Arg. Rhizophom mangle L. Sapiumuitidum (Monac h.) Lundell

{20) Paramo 1·egetation. This is a unique vegetatio n type growing in the highest mounta ins of Veracruz just below the permanent snow belt. There are no ecological studies published from Veracruz, but reports from other high mountains in Mexico may be extrapolated to a certain degree. The most import ant ecological factor at this altitude is low temperature. Very few plants can pass this strong filter. Soils at these altitudes are not well known, and the only profile, made by Johnso n (1970), is shown in Table X. The flora of this alpine vegetation (Fig.38) has been studied by Johnson, and the following species list been· taken from his work : Aspleuium-castaneum Schlecht. et Cham. Cuicus 11iva/is HBK. Drabajorullensis HBK. Draba myosotidioides Hems!. Festucas p. Gnaphalium inornatum DC. Gnaphalium oxypftyllum DC. Fig.37. A mangro ve swamp in M andinga . (After Yazquez , 197 1.)

Gnaphalium popocatepeciauum Sch. Bip. Miiltleubergia sp. Se11ecio chrysactis Sch. Bip. Se11ecio galeottii Hems!. Senecio orizabe11sis Sch. Bip. ex Hems!. Stipasp.

(21) Coastal dunes vegetation. There is a very well develop ed vegetation along the

.... 0

TABLE X 1

SOIL PROFILE 1N THE PARAMO VEGETAT ION OF THE I'ICO DE ORIZARA ( ALTITUDE

Depth

Hori-

(em)

ZOil

Colour when dry

+0-10

+10-20

20-30 30-40

40- 50

50-60

All

A12

Al3 Al3

when wet

Appar. Relar. densiry density

4,250 ~1); TH IS SOIL WAS IDE:-.ITU'IED AS AN ANDO SOIL {CRYPOSAMMf::"T )

Sand

------- ------- - ------· Silr Clay

r?oJ

(%)

Texrure

(%)

-·

~---·----

pH Toral C./o. Org. C/N C. E. C. Allo(1:2.5) N (%) maller (mequiv. / phone (%) (%) JOOg)

-·- -

0· :1::

~ :::: ..,

- --

I OYR 5/1.5 greyish-brown

10YR 3/!.5 very dark greyish-brown

!.27

2.35

89.0

8.8

2.2

sand

5.6

0.093

!.03

2.35

8.5

XXX

10YR 5/ 2 greyish-brown

10YR 3/ 2 very dark greyish-brown

!.37

2.49

87.4

11.4

1.2

sand

6.1

0.060 0.54

!.24

7.4

xxxx

IOYR 5/3 brown

10YR 3/3 dark brown

1.37

2.52

88. 1

10.0

!.9

sand

6.5

0.061

0.52

1.20

7.4

xxxx

10YR 5/3 brown

I OYR 3/3 dark brown

1.37

2.52

84.5

13.0

2.5

medium sandy Ioan1**

6.5

0.070

0.60

1.38

8.4

xxxx

lOYR 5/2 greyish-brown

lOYR 3/2 very dark greyish-brown

1.40

2.52

87.8

10.0

2.2

sand

6.6

0.074

0.59

1.36

8.0

xxxx

lOYR 5.5/2 I OYR 3/2 light very dark brownish-grey greyish-brown

1.53

2.55

87.1

10.9

2.0

sand

6.4

0.055

0.43

0.99

6.9

xxxx

____ ____.

60-70

70-80

10YR 6/1 light grey

++80-90

IOYR 6/1 light grey

*90-100

5YR 6/1 light grey

100-110

RyC

110-120

RyC

120-130

RyC

10YR6/ 2 10YR3/2 light very dark brownish-grey greyish-brown

1.60

2.56

86.6

12.5

0.9

sand

6.4

0.032 0.30

0.69

5.3

xxxx

lOYR 3/1 very dark grey

1.72

2.59

89.0

10.1

0.9

sand

6.2

0.012

0.08

0.19

3.1

xxxx

JOYR 3/ l very dark grey

1.73

2.58

88.3

9.8

1.9

sand

6.3

0.010 0.06

0.14

2.2

XXX

lOYR 3/1 • very dark grey

1.68

2.59

87.6

12.0

0.4

sand .

6.5

0.012

0.07

0.15

2.2

XXX

5YR 6/1 light grey

5YR2/2 dark reddish-brown

1.68

2.60

87.6

12.0

0.4

sand

6.4

0.010

0.03

0.07

1.8

XXX

5YR 6/ 1 light grey

5YR 2/2 dark reddish-brown

1.73

2.59

87.2

12.0

0.8

sand

6.4

0.010 0.03

0.06

2.0

XK X

5YR2/2 dark reddish,brown

1.71

5YR 6/ 1 light grey

8t-

't)

2.59

87.6

11.6

0.8

sand

6.4

0.010

0.01

0.02

2.0

XXX

'After J ohnson (1970). • . +dense roots; ++lowest limit of roots between 60 and 96 em; * coldest laye•; •• very coarse sand: 5.6 %; coarse sand: 5.4-8.6 % ; medium sand: 9.7-16.7%; fine sand : 27.1-31.4%; very fine sand : 24.5-32.7%.

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g 0

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1 142

A. GOM EZ-POM PA

ECOLOGY OF T HE VEGETAT ION OF VERACRUZ

143

coasta l dunes and beaches. This pioneer vegetat ion has been studied by Sauer (1967) and by Vazquez (197 1). The profile shown in Fig.39 is taken fro m the firs t author. The followi ng species are characterist ic of this vegetation type: Amcia .>plwerocep/wla Schlecht. ct Cham. Amarwu/ws gregii S. Wats. Andropogcm g/omera111s (Walt.) BSP. Andropogon litom/is Nash Bidens sqrwrrosa H ll K. Cakile lwrceo/ma 0. E. Schulz Ccmava!iamaritima (Aubl.) Thou. Casearianitida (L.) Jacq. Clmia c/wnraecri;·Joides Collad. Ctmia cinerea Cham. ct Schlecht. Cfrr)•soha!mtus icaco L. Cnidoscrdus frerbacwus (L.) Johnston Coccoloba uo•ifera L. Comme!ina erect a L. Crossopetcrfrmr !aJifolium Sw. Croton ptmctatus Jacq. Cyperus articulatus L. C)•perus /igu/aris L. Eragr-osti.1· damingensi.r (Pcrs.) Steud. Euplrorbicr buxifo/ia (Lam.) Small. Fimbristy!is spat!racea Roth Ipomoea pe;·-caprae (L.) Sweet Ipomoea .tto!onifera (Cyrill.) Po ir. Iva asperifo/ia Less.

Island vegetatio n is closely related to the vegetatio n in sand dunes, because most of the islands in the state do not have well-developed soi ls. The only island studied in detail up to now is the Isla Verde in front of the port of Veracruz where the diagram of Fig.40 was made (Lot, 1971). The foll owing species have been reported from this Island:

Fig.38. A view of the paramo vegetation at the Pico de Orizaba . (After Johnson, 1970.)

j GULF

10m

CLEARING

-~ ~

Jc1cquinia prmgens A. Gray Merremicr c/ircoidesperma Donn. Smith Nectcmc/ra cvricrcea (Sw.) Griscb. Oenot/rera drummonclii Hook. Ot/wke /indenii Bush Okenicr lrypogaea Schlecht. ct Cham. Opuntia dillenii (Ker-Gaw.) Haw. Pcr!afoxiatexalt(l DC. Pwricrmr repens L. Paspalum o•aginalum Sw. Pfry/a nodiflom (L.) Greene Pouteria dur/(llrdii (Standi.) Aubr. Psyclrotria nutans Sw. Randia acu!ea/a L. Raudia/aeleo•irens Standi. Sesuviw11 parlulacastrrrm L. Sporobolus virginicus (L.) Klmth Scaeo•ola plumierii (L.) Vahl Spartinapatens(Ait.) Muhl. Slemodia tomentosa (Willd.) Gray et Torrey Ut~io/a paniculala L. Verbesina o/it>acea Klatt Zamicrjinfuracea L.

;.; !,:{,g,.,#:-6~0

(!im,,,..,,;•.

Cassia chomaecr istoides· · · · · • Oenothero drummondii· ·· ···· •

Sport ina patens····· ·· ······ ·•

Uniolo paniculoto · ·· ··· ··· ·· ··•

1pomoeo ·pes-coproe - ..... · . · · •

Conavolio ma rit ima ·· ··· ·· ... ·• Coccoloba uvilera····· ........ · Chrysobalo nus icc co..... . ...... ·· - -· · ..- - - - - - - - - - - - - - - Ra ndle ocu leato· · ········ · · · ············ •·· ··· • ······• ···- ····· ·· ·• ·······Crossopetolu m latilollum- ... · · · · · · · · · · · · .. .... . .. .. . · ··· - -Nectondra corloceo-·· .•••.... · ··· ·•····· · ······ · • ····• ········ - ······Psychotria .nutons··· ....•.... · · · · · . ·. · · · · · · · · · · · · ...... . •.... · · . ... ··• Gliricid io seplum··· . ·. · · . . · · · .. · . .. · .... .. · · .. .. .... . · ·· ...... ..... .•.....••. ... ... . .. .. . . .... .

Fig.39. Vegetation profile of coastal dunes vegetation (north of Tuxpan). (After Sauer, 1967.)

Agave sp. Allanumda catlwrtica L. Ambrosia cumanensis H BK. Antigonon /eptopus Hook. et Arn. Balis maritima L. Caesalpinia bonduc (L.) Roxb. Canovaliamaritima (A ubi.) Thou. Cframaesyce buxifo/ia (Lam.) Small Cit!rarexylum e/!iplicum Sesse et Moe. Crota/aria spp. Eragrostis domingensis (Pers.) Steud. Fimbrisly/is spaJiwcea Roth Hymenocallis spp. Ipomoea stolonifera J. F. Gmel. ipomoea pes-cap rae (L.) Sweet

Iresine celosioides L. Jacquinia aura/Ciiaca Ait. Lagwrcularia racemosa (L.) Gaertn. f. Merremia discoidesperma Donn. Smith Nerium oleander L. Pandanus sp. Pauicrmr repens L. Plumeria acutifo/ia Poir. Raudia laelevirens Standi. Sesuvium porlulacas/rum L. Scaevo/a p/wnierii (L.) Vahl Suriano maritima L. Terminalia catappa L. Tournefortiagnapha!odes R. Br.

{22} Aquatic vegetation types. It is difficult to distinguis h this vegetation type from other types. M any of those mentioned before may be included in here, but since we

144

A. G6MEZ-POMPA

ECOLOG Y OF THE VEGETATION OF VERACRUZ

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145

into the same type, the dillerent names being applied to differen t floris tic compositions. _ Jn these "grasslands" higher plants are the most important constituents, but a few algae also make an important contribut ion to the ecological mosaic of these "grasslands". l n Fig.41 a profile of the relations of these different organisms in the different coral reeflagoons in Veracruz can be seen. The following plant species have been found in this vegetation type: Halodule wrightii Ascherson Ha/ophila decipiens var. pubcscens Hartog Ruppia maritima L.

Syringodium[ilijorme Kutzing Tlw/assia testudinum Koen ig ct Sims

Other aquatic vegetation types. In the Lagu na de Mandinga, Vazquez (1971) attempted to classify the aq uatic vegetation by dividing it into four groups: (J) vegetation with S\V

35m

plants fixed to the soil but wit h aerial parts; (2) vegetation composed of species with float ing leaves; (3) vegetation composed of plants with submerged leaves; and (4) free floating vegetation, not fixed in the soil. As constituents of the first group the followi ng species are mentioned:

Fig. 40. Vegetation profile oflsla Verde. (After Lot, 1971.)

lack a general study of the aquatic vegetation of Veracruz, we have not attempted to make a precise classification, bu t only to include some aquatic vegetation types not yet mentioned that are of special ecological interest.

. Marine vegetation. Several marine vegetation types have been recognized in coral reefs (Lot, 1971) by the name marine "grassland" or "ceibadales". In fact they all fall Al gae

Phonerogomoe

Halimeda opuntla

species of Caulerpa

Ha/odule wright//

;

Rhipocephalus phoenix

Cymapol/a b orbalo

Padfna varicgo t a

Crinum erubescens A it Echinolaena polystachya (HBK.) Hitch. E/eoclwris clegans (HBK.) Roem. et Schult. E/coclwris mutata (L.) Roem. et Schult.

Linmoclwris/fava (L.) Buchenau Pontederia sagitalla Prest Sagillaria lancifolia L. 'l)•plw angustifolia L.

In the second group these species are mentioned: Nymphaea amp/a (Salisb.) DC.

Nymplwea blanda G. Meyer

Of the third type these species a re menti oned : Cabombasp. Ccratophyllum demcrsw11 L.

Najas guada/upc11sis (Spreng.) Morong Ruppia marilima L.

These species arc mentioned as composi ng the free floating vegetation: Bacopa mo11ie1·i (L.) Wittst.

Pistia stratiotes L.

Thalassia testudlnum

Secondar y vegetation

50 Metr e s

Fig.41. Profile of a coral reef showing the distribution of the species. (After Lot, 1971.)

I have included secondary vegetation as a different type so that I may discuss it and not because I consider it a truly distinguishable vegetation type. There is, up to now, no classification available for typical second-growth vegetation. The reason is that it is the most complicated and variable grouping of species that can be found in any area, and i t varies from place to place as well as from time to time. The principal factor producing secondary vegetation is man and his activities in agriculture, cattle, and fo restry. Another problem with secondary vegetation is that there are no proven methods available to study it in a coherent manner. The only

146

A. G 6 M EZ-POMPA ECOLOG Y OF T HE VEGET ATION OF VERACRUZ

atte mpt to do so has been the method used in the ecological survey of the lowlands of the Gulf o f M exico (Mira nda ct al. , 1967). From this work we have a large amoun t of data abo ut the presence of certain species in ~ilferent stages of d ist urbance in an area wit h a known vegetation type and soil. In this survey the first papers includ ing data from secondary vegetation appear (Anonymo us, 1960/ 1969; G omez-Pom pa ct al. , 1964a, b; Sousa, 1964; Sarukhfm, 1964). This work is discussed here because some of the data from tha t survey and from ihe p u blications derived from it are from: or applicable to localities in Veracruz. Unfortuna tely, the area covered by these earlier studies did not cover the whole sta te o f Veracruz, and almost no informat ion was obtained from a ltitudes higher than 1,000 m and dlier than 1,500 mm of precipitation. In more recent studies on seconda ry vegetation (Gomez-Pompa, 1971), the classification scheme has been broadened to incorpo rate more variables that can be studied experimen tally. To present a list of the different · species in secondary vegetation derived from differen t vegetation types in the different regions could be a goal for a future paper, b ut here I can only present a list of the genera which are basically represente d by secondary species .in Veracruz: Apeiba Artilrostemma Argemone Antigonon Alibcrtia Amorrmthus k·istolochia Asclepias Ailws Aster /)_cal;•pha Adelia Andropogon Acacia Aescltynomene Anoda Bixa Bromelia Bauhinia Bunclwsia Borrcria Byffneria Belotia Cydista Cordia Canna Cleo me Cochlospermum Combrctum Commclina Calea

Conyza Cirsium Carex Cypems Cnidosculus Croton Casearia Callirmdra Cenchms Canavalia Cassia Centrosema Crotalaria Cuphea C/idemia Conostegia Ccdrela Cissampelos Cecropia Cmsea CardiospermUI/1 Cestrum Cost us Chenopodium Davilla Dioscorea Dalea Desmodium Eupatorium Euphorbia Eragrostis

EriosenliJ Erythrina Eugenia Ficus Gono lobus Gliricidia Gouania Guozuma Hamelia Heliconia Hyptis Hoffmania Hibiscus Heliocarpus ·Indigo/era Inga Ipomoea Iresine Jatropha fii iiCliS

Kallstroemia Lasiacis Lonchocarpus Lygodium Luehea Linaria Lantana Lippia Maranta M arsdenia Melampodium

Mikania Momordica Muntingia Mimosa Mucuna Malache Malvaviscus Miconia Melochia Myriocarpa Neurolaena Ochroma 0 /;•ra

Oxa/is Perrolletia Parthcnium Porophyllum Plettraltfhodeltdrolt Ptmicum Paspalum Phaseolus Pithecellobium Psidium Pisonia Passiflora

J!e.JiJ1e.J'itl

Pilyto/acca Piper Po/ygu/a Pa/icourea l'syclwtria Picramnia Physalis Pilea Phyla Rolliuia RueIlia Raull'o/jia Rvurea Rhyuchosia Ril ina Rvmleletia Russelia Se1jania Sesuvium Schoepjia Scleria Sida Smilax 1

147

Solanum Spoudias Stacl!ytarplteta Stemmadenia Stigmapltyl/on Taberuaemontmw Tecoma Toumefortia TnjJOKtmdm Trophis Tithonia Turbina Tetracera Teucrium Tibouchiua Triumfetta Trema Urem Verbesina Vismia Vemonia Wissaclu/a Xant/wsoma Zomia

References Aguilera, N ., 1958. Suelos. In : Los Recm:.'iOS naturales del Sureste y su Aprovec!tam ieuto, 2. Edic. Inst. Mex. Rcc. Nat. Renov., Mexico City, pp.l77-212. Anonymous , 1960/ 1969. Informes de Ia Comisi6n de £studios sobre Ia Eco/ogia de Dioscoreas. Tnst. N ac. Inves t. Forcstales, Mexico, Mexico City, 5 vel. Balls, E. K., 1939. Plant hunting in Mexico. Card. Citron., 3 ( 105): 122-123;138-:139;1_52153. . Baynton, H. W., 1968. The ecology of an elfin fo rest in Puerto Rico, 2. The mtcrochmate ofP1co del Oeste. J. Amold Arboretum, 49:419-430. · Beard, J. S., 1953. The savanna vegetation of northern tropical ~m~rica. Eco/. Mon~g!·. , 23 :149-215. Chiang, F., 1970. La Vegetacion de Cordoba, Ver. Thesis Fnc. Ctcncias~ UNA~, Mextco, 47 pp. Cuanalo, H. and Aguilera, N., 1970. Los suelos de Ia cuenca mtermedm del RIO Papaloapan. Pub!. Esp. Inst. 1111•. Nac.For. Mex., 6:1-62. Garcia, E., 1970. Los eli mas del estado de Veracruz. Anates lnst. Bioi. Univ. Nac. Mex., Ser. Bot., 41 . (1):3-42. Gentry, H . S., 1942. Rio Mayo plants. Camegie l nst. Wash., Pub/., 527 :t-328. Gentry, H. S., 1946. Sierra Tacuicham ona-a Sina loa plant locale. Bull. Torrey Bot. C/ub,73(4):3 56362. Gomez-Pom pa, A., 1965. La vegetacion de Mexico. Bot. Soc. Bot. Mex.,29:76-J20.. Gomez-Pom pa, A., 1966. £studios bottinicos en/a Region de Misantla, Veracmz. Ed1c. In st. Mex. Rec. Na t. Renov., Mexico, Mexico City, I 73 pp. Gomez-Pom pa, A., 1967. Some problems of tropical plant ecology. J. Arnold Arboretum, 48(2):104121. 'cal Gomez-Pom pa, A., 1971. Posible papel de Ja vegetacion secundaria en 1a evolucion d e Ia J1 ·ora trop1 · Biotropica, 3: 125-135. Gomez-Pom pa, A., VlUquez Soto, J. and Sarukhan, J., 1964a. Estudios ecol6gicos en las zonas tropicales calido humedas de Mexico. Pub/. Esp. Inst. Nac. lnv. For. Mex., 3:1-36.

14S

A. GOM EZ-POMPA

Gomcz-Pom ra, A., Hcrmindcz. P., L. and Sousa, S. M., l%4b. Es!udio fi!occoltigico de Ia cuenca in1crmedi:1 del Rio Papaloapan. Pub/. Esp. Ins/. Nac. !111·. For. Mh·., 3:37- 90. Gomez-Po m pa, A. and Ncvling, L. 1., 1970. La llora de Veracruz. Anales Ins/. Bioi. Uni••. Nac. lv/i!x., Ser. 13oL, 4 1( 1) : 1-2. Howard, R. A., 1968. The ecology of an elfin fo rest in l'tiCrlo Rico, I. ln!mduction and composition studies. J. Amold Arboretum, 49(4):38 1-41 &. Ja nzen, D. H., 1970. Jacquiuia fi/1/I.!feus, a heliophilc from the understory of tropical d eciduous forest. Biotropica, 2(2): 11 2- 119. Johnson, E. L., 1970. Mmfogcucsis y Clasifrcacivu de Algunos perfiles de Suelos deril•tulos de Ceuizas volcanicas del Pica de Orizaba, Puebla y Veracruz. Thesis Fac. Ciencias, UN AM, Mexico, 78 pp. leon, C. J . and Gomez-Pom pa. A., 1970 . La vcgelacion del surcstc de Veracruz. Pub/. Esp. lust. Nac. btv. For. Mex., 5:15-48. Lol, A., 1971. Estudios sobre fancr6gamas marinas en las ccrcanias de Veracruz, Ver. Anales Ins/. Bioi. Unil•. Nac. Mi:x., Ser. Bot., 4 2 (1): 1-48. Lundell, C. L., 1937. The vegetation of Pclen. Camegie lust. Wash. , Pub/.,478: 1- 244. Miranda, F., 1955. Fonnas de vida vcgelales y el problema de Ia delimitaci6n de las zonas aridas de Mexico. In: M esas lledonda.\· sabre Problema.,· de las Zonas tiridas de Mexico. Edic. lnst. Mex. R ec. Nat. Renov., Mexico City, pp.85-1 19. Miranda, F ., 1959. Posible significaci6n del porcentajc de gcneros bicontincnla les en America tropical. Anales lmt. Bioi. Unh•. Nac. Mex., 30: 117- 150. Miranda, F. and H ernandez X., E., 1963. Los lipos de vegelacion de Mexico y su clasificaci6n . Bot. Soc. B ot. Mh:., 28:29-179. Miranda, F. and Sharp, A. J., 1950. Characlerislics of !he vegetal ion in certain temperate regio ns of eastern Mexico. Ecology, 31 :313-333. Miranda, F., G6mez-Pom pa, A. and Hernandez, X., E., 1967. Un metoda para Ia invesligaci6n ecol6gica de las rcgioncs lropicales. Ana/es lnst. Bioi. Univ. Nac. Mex. , Ser. Bot., 38 ( 1):101-110. Mohr, E. C. J. and Van Baren, F. A., 1954. Tropical Soils. Interscience, Londqn, 498 pp. Mosii\o, A. P. and Garcm, E., 1966. Evaluaci6n de Ia sequia in!racstival en Ia Republica Mexicana. Uni6 n Geognifica lnlcrnaciona l. Confc rencia Regional Lal inoamerican a . Edic. Soc. ·Mex. Geogr. Estat!is., 3:500-516. Pennington, R. D. and Sarukh{m, J., 1968. Arboles tropica/es de M exico. lost. Nac. Invest. Forestales, Mexico, Mexico City, 413 pp. Ramos, C., 1971. Vegetacion de Ia Zona arida Veracmzana. Thesi; Fac. Ciencias, UNAM, Mexico, Mexico City, 30 pp. Rzedowski, J ., 1963. El exlremo boreal del bosque tropical siempre verde en Norteameric a Conlinenlal. Vegetatio, 11(4):173-198. Rzedowski, J. and McVaugh, R., 1966. La vege1aci6n de Nueva Galicia. Coutrib. Uni••. Mich. Herb., 9(1): 1- 123. Saru khan, J., 1964. Estudio succsional de un area talada en Tuxlepcc, Oax. Pub/. Esp. l ust. Nac. !nv. For. Mex., 3:107-172. Sauer, J., 1967. Geographic reconnaissan ce of seashore vegetation along the Mexican Gulf coast. Coastal Stud. Inst., La. State Univ., Tech. Rep., 56:59 pp. Solo, M., 1969. Consideraciones ecoclimliticas del Estado de Veracmz. Thesis Fac. Ciencias, UNAM, Mexico, Mexico City; 43 pp. Sousa, S. M., 1964. Estudio de Ia vegetaci6n secundaria en Ia region de Tuxtepec, Oax. Pub/. Esp. Just. Nac. !nv. For. Mex., 3:91-105. Sousa, S. M ., 1968. Ecologia de las leguminosas de Los Tuxtlas, Veracruz. Aua!es Just. Bio i. Uuiv. Nac. M ex., Ser. Bot., 39(1):121-160. T o ledo, V., 1969. Diversit!ad de £species en/as Se/vas altas de Ia Platticie Costera del Golfo de Mexico. Thesis F ac. Ciencias, UNAM, Mexico, Mexico City, 55 pp. Vazquez, C., 1971. La vegetaci6n de Ia laguna de Mandinga, Veracruz. Anates !nsf. Bioi. Univ. Nac. Mex., Ser. Bot., 42:49-94. Whiteside, E. P., 1960. Observations 011 Great Soil Groups in Humid Tropical Portions of Mexico. Rockefeller Found., Mexico (unpublished ). W illia ms, L. L., 1939. Arboles y arbustos del Istmo de Tehuantepec , Mexico, Lil/oa 4:137-171.

Chapter 5

The Phytogeography and Vegetation of Chiapas (Mexico) DENNIS E. DREEDLOV E Department of /Jot any, Cali}imtia Academ y of Sciences, San Francisco, Calif. (U.S.A.)

Summary Chiapas has one of the most diverse and la rgest flo ras of any of the Mexican states. The study of this vegetatio n is facilitated by reference to the seven physiographic regions outlined by Mulleried (1957). These regions have consistently sim ilar fl oristic association s. Th1 ee of these regions, the Central H ighlands, the Central Depression and the Northern Highlands , are restricted to Chiapas. T he Sierra Madre a nd the Eastern H ighlands extend southward into Guatemala while the P acific and Gulf Coastal Plains are southern extensions of large central Mexican regions. T he result is that many of the floristic associations i11 Chiapas are unique without wiclespread relationships. The classification of the vegetationa l formations of tropical America establi shed by Beard (1944) is remarkably adequate for t he vegetation ofChiapas . Some adjustment is necessary to account for the temperate forests of the Central Highlands and the Sierra Madre. T here are nineteen fo rmations described in this work and they are arranged into five formation series. The four optimum formations are characterized by a climate in which significant rain falls in every month of the year and a well drained substrate. The six seasonal formations also occur on well drained soils. .The climate, however, is marked by a distinct dry season of 2-6 months. The wet-land forest a nd treeless fo rmations are much less natural groups. T hey are in general narrowly restricted in distributio n and dependent on some special feature of the environme nt. The dominant and most common species of trees and shrubs are listed for each formation. Second growth formations are common and very d iverse, and one example of t hese is described.

Introduction Chiapas is the southernm ost state of Mexico, situated on the Pacific Coast between the Guatemala border and the Isthmus of Tehuantep ec, and occupying more than 74,000 sq. km. The present population of Chiapas is near 1,500,000, with almost one half of this total being Mayan agriculturalists living in dispersed hamlets. The climate is diverse, ranging from semi-desert to rainforest and fr om sea-level with stands of