Andean aquatic vegetation in central Bolivia - Molina et al. 2007

Phytocoenologia

37 (3Ð4)

753Ð768

BerlinÐStuttgart, December 21, 2007

Andean aquatic vegetation in central Bolivia

by Jose´ Antonio Molina, Gonzalo Navarro, Nelly De la Barra and Ana Lumbreras, Madrid (Spain) and Cochabamba (Bolivia) with 3 figures and 2 tables Abstract. This work focuses on the floristic and ecological study of aquatic Andean vegetation in central Bolivia at different levels. The local level was studied by means of the plant-community distribution and composition in a typical Andean hydrosere. This showed that water-plant communities including isoetid vegetation, helophytic vegetation and low amphibious vegetation could be distinguished within the aquatic environment.

The next step involved collecting all the phytosociological information from central Bolivia, in addition to our own phytosociological releve´s, to make numerical analyses. At a regional level, hierarchical classification showed floristic variability in two main groups: one with aquatic and amphibious vegetation characterized by Isoetes aff. lechleri, Ranunculus flagelliformis or Callitriche heteropoda, among others; and another with aquatic, amphibious, and also helophytic vegetation characterized by Zannichellia andina, Potamogeton striatus or Scirpus tatora, among others. The phytogeography of the characteristic plants indicates that the first group is mainly composed of releve´s from orotropical locations of the Eastern Ranges, whereas the second for the most part comprises oro- to mesotropical locations in the western Andean ranges, Altiplano, Vacas Basin (eastern ranges) and dry inter-Andean valleys. The relationships between the distribution of water plants and the physical-chemistry of the water were carried out by CCA, and showed that the first group occurs in non-mineralized waters while the second group occurs in mineralized waters. All of this leads to the description of 14 plant communities from a floristic and ecological viewpoint.

Keywords: bioindicators, CCA, central Andes, classification, phytosociology, water-plant community.

1.

Introduction

Wetlands include swamps, bogs, marshes, mires, lakes and floodplains, and cover an estimated total area of nearly three million square kilometers of the earth’s surface (Groombridge & Jenkins 1998, http://www.unep.org).

They play an important role in ecology, as they are intermediate areas between water and land ecosystems and perform a range of important functions including the transfer and storage of water, bio-geochemical transformations, maintaining atmospheric carbon balance, primary productivity, decomposition, and sustaining community/habitat. Mountain wetlands include a wide range of lakes, rivers, streams, marshes, peatlands and karst DOI: 10.1127/0340-269X/2007/0037-0753 0340-269X/07/0037-0753 $ 4.00 ” 2007 Gebrüder Borntraeger, D-14129 Berlin · D-70176 Stuttgart

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systems, which vary greatly in size and permanence. They are extreme environments, which are particularly fragile and vulnerable to external pressures.

The Bolivian Andean wetlands include aquatic vegetation, helophytic vegetation, amphibious vegetation, and peat vegetation in mires (Ruthsatz 1995, Navarro 2002, De la Barra 2003). There have been few studies using phytosociological methodology on aquatic environments in Bolivia (Liberman et al. 1988, Liberman et al. 1991, Seibert & Menhofer 1991, 1992, Navarro 2002, De la Barra 2003). We are unaware of any on the subject of ecological relationships between aquatic plant community distribution and the physical-chemical properties of the water but some regional antecedents have been found in Ecuador and Chile (Terneus 2002, San Martı´n et al. 2003). This work focuses on the vascular water-plant vegetation of the central Andes of Bolivia, and includes an integral study on both the local and regional scale. The main goals of this work are: a) to characterize a typical Andean hydrosere in order to determine the spatial distribution of water plant communities along a hydric gradient; b) to gather and analyze the information available on aquatic vegetation in Andean central Bolivia; c) to identify the main ecological drivers influencing the distribution of aquatic vegetation; d) to propose a classification based on floristic and ecological criteria for the high-Andean littoral plant communities of central Bolivia.

2.

Methods

We selected a representative high mountain wetland area in central South America (Bolivia) to carry out a hydroseral study. It is located in the Tunari Range (central Bolivia) with an average altitude of 4,200 m a.s.l. (17∞ 14⬘Ð 17∞ 15⬘ and 66∞ 18⬘Ð66∞ 21⬘). The prospected area is about 5 km2 and includes a system of lakes and small rivulets above the timberline, with an oligotrophic soil environment and a mean annual temperature of about 4 ∞C. According to Rivas-Martı´nez et al. (1999) the bioclimatic characterization of the area is orotropical pluviseasonal humid. Andean high mountains have a rainy period (JanuaryÐFebruary), which falls between two warm periods. The second warm period, after the water recharging of the wetlands, is when the perennial shallow-water amphibious vegetation develops, characteristic of Andean tropical areas. Species richness, average height of the community and dominant growth form were calculated for each plant community type identified. The releve´s were synthesized and then numerically classified (with the exception of Isoetes aff. lechleri swards, due to lack of data), in order to determine plant-community relationships and spatial distribution.

63 phytosociological releve´s covering Andean central Bolivia obtained from both bibliographical sources and our own field data carried out in 2005 and done according to classical phytosociological procedures (BraunBlanquet 1979, Ge´hu & Rivas-Martı´nez 1982) were gathered in a raw table. Numerical classification was carried out to detect floristic similarities

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and characteristic species as well as to determine the variability factors of the data. The abundance/dominance values of the 6-grade Braun-Blanquet scale in the tables were transformed into a 0Ð9 ordinal scale according to van der Maarel (1979). The classification of the releve´s was done by using the incremental sum of squares method and the chord distance as an algorithm of distance. The computer program used was Syn-Tax (Podani 2001).

Canonical correspondence analysis (CCA) has found widespread use in aquatic sciences, particularly to identify environmental variables, which are important in the determination of the community composition (ter Braak & Verdonschot 1995). This method was used to seek relationships between plant distribution and the physico-chemical properties of the water, and subsequently to find plants and plant communities suitable for use as bioindicators of the nutrient status of the water. Data were taken from bibliographical sources carried out in a multidisciplinary wetland study covering a transection of the highlands of central Bolivia, which include most of the combined factors of relief, geology and climate (Acosta et al.

2003, De la Barra 2003). Initially, the analyses consisted of two matrices of 16 samples with 24 plants (the species matrix) and 15 physical-chemical features of the water (the environmental matrix). Water variables were: transparency, pH, Electrical Conductivity (EC), Bicarbonates, Chlorides, Phosphates, Nitrates, Sulphates, Total Dissolved Solids (TDS), Ca, Cl, Fe, Mg, K, Na, Si. After excluding the outliers the analysis focused on 14 samples, 13 species and 13 physical-chemical variables of the water. The computer program used was CANOCO (ter Braak & Smilauer 1998).

Finally, with all the previous results we were able to characterize and classify the aquatic vegetation of central Bolivia from a floristic and ecological viewpoint. Plant nomenclature is according to Brako & Zarucchi (1993). Although it was not the aim of this work to provide a taxonomical revision, the description of type plant communities includes association names as synonyms. The terminology of water-plant life forms is according to Hartog & Segal (1964).

3.

Results and discussion

3.1

Hydrosere composition

An example of hydrosere composition in the central Bolivian Andes is shown in Fig. 1a. The catena includes seven plant community types: (1) Festuca humilior meadow “pajonal”, (2) Plantago tubulosa flat peat bog “bofedal plano”, (3) Distichia muscoides cushion-like peat bog “bofedal pulvinular almohadillado”, (4) Deyeuxia chrysantha-Deyeuxia eminens bunch-grassland swamp “pajonal inundado”, (5) amphibious vegetation of Lilaeopsis macloviana in temporary waters, (6) aquatic vegetation of Ranunculus flagelliformis in shallow waters, and (7) isoetid vegetation of Isoetes aff. lechleri in deep and permanent waters. Species richness increases along the rising elevation in the microtopographic gradient (Table 1); the aquatic communities have fewer species and the peripheral Festuca humilior

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Fig. 1. Plant-community composition of an Andean hydrosere on oligotrophic environmental wetland in central Bolivia (Tunari range). a) Schematic catena; b) Synthetic classification of the plant communities. And 1: Festuca humilior meadow; And 2: Plantago tubulosa flat peat bog; And 3: Distichia muscoides cushion-like peat bog; And 4: Deyeuxia swamps; And 5: Lilaeopsis macloviana community; And 6: Ranunculus flagelliformis community; And 7: Isoetes aff. lechleri sward (not included in the dendrogram).

meadows have more. The taller vegetation belt corresponds to the border water communities of Deyeuxia sp. pl. swamps. Physiognomically, the upper belt is dominated by caespitose hemicryptophytes; the belts of intermediate flooding consist of plant communities dominated by hemicryptophytes (rosulate or caespitose) or pulvinulate chamaephytes; and the aquatic habitats are composed of helophytes and radicant hydrophytes. Within the water-plant communities dominated by radicant hydrophytes, the isoetid vegetation, which is specially adapted to oligotrophic conditions (Smolders et al. 2002), is common in permanent waters. This hydrosere is typical of the central Bolivian Andes in wetlands of non-mineralized waters (Na-

Andean aquatic vegetation in central Bolivia

Table 1. Local hydrosere features in an Andean catena of the Tunari range.

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varro 2002, De la Barra 2003) and similar to others studied in the north of Bolivia (Seibert & Menhofer 1991), central Peru (Gutte 1980) and north of Chile (Ruthsatz 1995).

The classification of the samples in the hydrosere shows two main subgroups (Fig. 1b). Group A comprises hygrophilous meadows (Calamagrostietea vicunarum Rivas-Martı´nez & Tovar 1982) and bog plant communities (Plantagini rididae-Distichietea muscoidis Rivas-Martı´nez & Tovar 1982), and group B includes aquatic vegetation (Limoselletea australis Cleef 1981, Potametea Klika in Klika & Nova´k 1941). The higher dissimilarity level in the dendrogram (also seen in the hydrosere itself) indicates that the most important step in the segregation of wetland habitats is that which separates aquatic plant communities growing on subhydric gyttja-type soils (sensu Kubiena 1952) from the peat and meadow plant-communities developing on histosols and gleysols (sensu FAO 1977). In this case, after soft water vegetation, the swamps of Deyeuxia sp. pl. (caespitose hemicryptophytes) or occasionally of Scirpus tatora (helophyte) are the formations which act as precursors of the soil formation (Navarro 2002). Aquatic environments are occupied by water-plant vegetation arranged in a zonation which is related to depth under stable levels (van der Valk & Davis 1978) and to the duration and frequency of inundation and the depth and duration of flooding events (Casanova & Brock 2000).

3.2

Classification of releve´s

Numerical classification of the releve´s from aquatic habitats in central highmountain Bolivia displayed two main clusters (A and B) within which a segregation between aquatic and amphibious vegetation samples can be seen (Fig. 2). The second cluster also comprises helophytic vegetation samples.

Cluster A includes releve´s characterized by hydrophytes such as Isoetes aff. lechleri, Ranunculus flagelliformis, Callitriche heteropoda, Nitella sp., Isoetes boliviensis and Elodea potamogeton. Cluster A also includes samples characterized by amphibious plants such as Lilaeopsis macloviana, Lachemilla diplophylla and Cotula mexicana. Cluster B includes three subgroups: releve´s characterized by hydrophytes such as Zannichellia andina, Potamogeton aff. striatus and Azolla filiculoides, among others; samples from amphibious habitats characterized by Ranunculus cymbalaria and Limosella aquatica; and releve´s characterized by helophytes such as Typha domingensis and Scirpus tatora. From a geographical viewpoint, cluster A comprises water-plant communities mainly from eastern ranges, and amphibious communities from both eastern and western ranges. Cluster B includes aquatic communities mainly from the eastern ranges (Vacas Basin), amphibious communities from the Altiplano and eastern ranges, and inter-Andean dry valley “totora” swamps. From a bioclimatic viewpoint cluster A contains releve´s from orotropical belt, whereas cluster B groups samples from mesotropical to orotropical belt. The higher dissimilarity level in the dendrogram may be related to geophysical and climatic factors. Water chemistry and nutrient availability are known to be additional factors influencing the

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Fig. 2. Clustering analysis of 63 phytosociological releve´s of aquatic environments from the central Bolivian Andes. A: Altiplano; IDV: inter-Andean dry valleys; ER-Ti: Eastern ranges, Tiraque; ER-Tu: Eastern ranges, Tunari; VB: Vacas Basin, WR: Western ranges.

distribution and composition of wetland plant communities (Malmer 1986, Gacia et al. 1994, Bragazza 1999, Terneus 2002, Miserere et al. 2003).

Specifically, the bioclimate and the geomorphological nature of the region have been identified as the principal controlling factors of the planktonic community distribution in central Bolivia (Acosta et al. 2003).

3.3

Gradient analysis

The first CCA analysis showed two sites acting as outliers in relation to the rest of the sites. These two sites correspond to the Ruppia filiformis community related with higher values of pH, bicarbonates and sulphates; and to the Marsilea cf. ancylopoda community related with higher values of TDS and Ca, and high values of phosphates and Fe. A subsequent CCA analysis, which did not take into account, these communities showed an ordination diagram (Fig. 3) in which two main floristic contingents are distinguished. The first, centered around Isoetes sp., Nitella sp., Callitriche heteropoda, Elodea potamogeton and Crassula venezuelensis, has higher weighted averages for transparency and nitrates for all the species shown.

On the opposite side, the second group includes most of the remaining species such as Zannichellia andina, Potamogeton aff. striatus, Ranunculus cymbalaria, etc. which largely occur at higher averages of a series of water

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Fig. 3. Species-conditional triplot based on a canonical correspondence analysis displaying 54 % of the inertia in the abundances and 55 % of variance in the weighted averages of species with respect to the environmental variables. The eigenvalues of axis 1 (horizontally) and axis 2 (vertically) are 0.69 and 0.39, respectively; the eigenvalue of the axis 3 (not displayed) is 0.26. Quantitative physical-chemical variables of the water are indicated by arrows. The abbreviations are according to those used in the text (see Methods). The species names are abbreviated to the part in italic as follows: Azolla filiculoides, Callitriche heteropoda, Crassula venezuelensis, Elodea potamogeton, Isoetes species, Limosella aquatica, Limosella subulata, Myriophyllum quitensis, Nitella species, Ranunculus cymbalaria, Ranunculus psycrophilus, Potamogeton aff. striatus, Zannichellia andina. Localities: 1: Laguna HuanËœa Khota; 2: Laguna Parina Khota; 3: Laguna Canasa; 4: Laguna La Abuela; 5: Laguna Wara Wara; 6: Laguna Kuyuntani; 7: Laguna KewinËœa Kocha; 8: Laguna Totora Khocha; 9: Laguna Pacha Khocha; 10: Laguna Muyu Loma; 11: Laguna Juntutuyo; 12: Laguna Acero Khocha; 13: Laguna Parko Khocha; 14: Laguna Kollpa Khocha.

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features such as bicarbonates, pH, Mg, Na, phosphates, sulphates, etc.

Within this second pool it should also be noted that Potamogeton aff. striatus, and Azolla filiculoides occur at higher phosphate values, whereas Ranunculus cymbalaria occur at high values of Na, Mg, Cl and K, among others. Based on the water chemical typology of Maldonado (2002), plants such as Isoetes sp., Nitella sp., Callitriche heteropoda, Elodea potamogeton and Crassula venezuelensis are drivers or characteristic species of non-mineralized waters. Zannichellia andina, Potamogeton aff. striatus and Ranunculus cymbalaria are indicators of mineralized waters. Ranking environmental variables according to their importance by the marginal and conditional effects of the flora showed that transparency of water, content of bicarbonates and TDS adequately explained the differences in hydrophytes between the ranges. In high-Andean Ecuadorian lakes, substrate type and sulphates concentration are among the best environmental parameters to explain the changes in the floristic composition (Terneus 2002).

3.4

Description of the plant communities

Lemna minuta-Lemna gibba community (= L em ne tu m m in ut o- gi bb ae Liberman Cruz, Pedrotti & Venanzoni 1988) Table 2, col. 1 Floating water plant community locally characterized by 3 Lemna species (Lemna minuta, Lemna gibba and Lemna valdiviana) and growing in still, nutrient/salt-rich water bodies. Mainly occurring on the Altiplano (Liberman et al. 1988, Liberman et al. 1991) within the xeric orotropical dry to semiarid bioclimate where it is common in lakes Titicaca, Uru-Uru and Poopo´. Locally it reaches the inter-Andean dry valleys of Cochabamba with a xeric Mesotropical bioclimate. This community has been also reported from high-Andean Peru and Chile (Gala´n de Mera et al. 2003, Luebert & Gajardo 2005).

Isoetes lechleri community (= I so et et um le ch le ri Gutte 1980) Table 2, col. 2Ă?5 Isoetid plant-community characterized by Isoetes aff. lechleri which forms swards on high-Andean lake shores. It grows in non-mineralized permanent, transparent waters. Subhumid and humid pluviseasonal orotropical. High-Andean lakes of the center-north of the eastern ranges of Bolivia (La Paz and Cochabamba) (Seibert & Menhofer 1991, De la Barra 2003). The Isoetetum lechleri association has been cited from central Peru (Gutte 1980).

Callitriche heteropoda-Ranunculus flagelliformis community (= R an un cu le tu m f la ge ll if or mi s Seibert & Menhofer 1992; C al li tr ic ho he te ro po da e- Ra nu nc ul et um fl ag el li fo rm is G. Navarro 2002 in G. Navarro & Maldonado 2002)

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Table 2. Synopsis of the water-plant communities in central Bolivia.

1: Lemna minuta-Lemna gibba community, dry inter-Andean valleys [De la Barra (2003), Table 3, rel. 16Ð17 pro parte]. 2Ð5: Isoetes lechleri community; 2: Tunari range [De la Barra (2003), Table 2, rel. 7Ð9, 18Ð19]; 3: Tunari range (own releve´s); 4: Tiraque range (own releve´s); 5: Taquin˜a range (own releve´s). 6: Callitriche heteropoda-Ranunculus flagelliformis community, Tunari range (own releve´s); 7: Lachemillo diplophylla-Lilaeopsis

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Table 2, col. 6 This community is characterized by small hydrophytes such as Callitriche heteropoda and Ranunculus flagelliformis, both widely distributed throughout the central Andes and growing in non-mineralized, transparent, shallow water. It develops in contact with the swards of Lachemilla diplophylla and Lilaeopsis macloviana in temporary flooded substrates and often gives way to the Isoetes lechleri community in deep waters. Subhumid and humid pluviseasonal orotropical. High-Andean lakes of the center-north of the eastern ranges of Bolivia (La Paz and Cochabamba) (Seibert & Menhofer 1992, De la Barra 2003). Similar communities have also been cited from the center (R an un cu le tu m m an do ni an i) and south of Peru (R an un cu le tu m l im os el lo id es ) (Gala´n de Mera 1995, Gala´n de Mera et al. 2003). In rather deep, oligo-mesotrophic waters in lakes, and waters released by the peat bogs, communities characterized by Myriophyllum quitensis (M yr io ph yl le tu m q ui te ns is Seibert & Menhofer 1992) have been recognized in the central Andes. In eutrophized environments, this vegetation is characterized by the presence of Elodea potamogeton (E lo de et um p ot am og et on is Seibert & Menhofer 1992) (Gala´n de Mera et al. 2003).

In our study zone, communities dominated by Elodea potamogeton have been found in poorly-mineralized moving water.

Lachemilla diplophylla-Lilaeopsis macloviana community (= C ot ul o m ex ic an ae -L il ae op si et um ma cl ov ia na e G. Navarro in G. Navarro & Maldonado 2002; A lc he mi ll o d ip lo ph yl la e- Li la eo ps id et um an di na e Rivas-Martı´nez & Tovar 1982; Elatine triandra-Crassula venezuelensis community De la Barra 2003 pro parte; Lilaeopsis andina community Seibert & Menhofer 1992) Table 2, col. 7 This community forms swards of small helophytes growing on the shallower margins of non-mineralized lakes on slime, or combined with fine sand substrates. This habitat may dry partially or totally at the end of the dry season, between August and October. Subhumid and humid pluviseamacloviana community, Tunari range (own releve´s); 8: Alopecurus hitchcockii-Juncus stipulatus community, Tiraque ranges (own releve´s); 9: Ranunculus uniflorus-Potamogeton filiformis community, Altiplano [De la Barra (2003), Table 1, rel. 3, 9]. 10: Ruppia filifolia community, dry inter-Andean valleys [De la Barra (2003), Table 3, rel. 9Ð10]. 11: Ranunculus cymbalaria-Zannichellia andina community, Altiplano [De la Barra (2003), Table 1, rel. 4Ð8]. 12: Zannichellia andina-Potamogeton aff. striatus community, Vacas Basin [De la Barra (2003), Table 3, rel. 1Ð8]. 13: Zannichellia andina-Potamogeton pectinatus community, dry inter-Andean valleys [De la Barra, Table 3, rel. 12Ð13, 15Ð16]. 14: Triglochin palustris-Lilaeopsis macloviana community, Altiplano, [De la Barra (2003), Table 1, rel.

2]. 15: Marsilea cf. ancylopoda community, dry inter-Andean valleys [De la Barra (2003), Table 3, rel. 24Ð25]. 16: Pistia stratiotes-Eichhornia crassipes community, dry inter-Andean valleys [De la Barra (2003), Table 3, rel. 19Ð20]. 17: Scirpus tatora community, dry inter-Andean valleys [De la Barra (2003), Table 3, rel. 11, 23, and 16Ð17 pro parte].

Columns resulting from only one releve´ are transcribed in italics.

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sonal orotropical. High-Andean lakes of the center-north of the eastern ranges of Bolivia (La Paz and Cochabamba) (Seibert & Menhofer 1992, De la Barra 2003). It is also present in the pluviseasonal high-Andean ranges of central and southern Peru (Rivas-MartĹ´nez & Tovar 1982). On muddy substrates in shallow waters (5�10 cm depth) the Crassuletum connatae association has been described in northern Peru (Seibert & Menhofer 1991).

Alopecurus hitchcockii-Juncus stipulatus community Table 2, col. 8 Amphibious community floristically characterized by Juncus stipulatus which appears to replace the latter community in rather deeper waters and in the high supratropical and low orotropical belts. Subhumid and humid pluviseasonal high-Andean lakes of the center-north of the eastern ranges of Bolivia (La Paz and Cochabamba).

Ranunculus uniflorus-Potamogeton filiformis community (= Myriophyllum quitensis-Potamogeton filiformis community G. Navarro & G. Navarro & Maldonado 2002) Table 2, col. 9 Aquatic plant-community composed by small helophytes such as Ranunculus uniflorus (endemic to the high center-western Andes) and hydrophytes such as Potamogeton filiformis. It grows in rather deep, mineralized waters. Dry xeric orotropical and also subhumid pluviseasonal orotropical.

Orotropical lakes of the Altiplano, as well as more locally present in the center-south of the western range. It inhabits channels and ponds in peat bogs with hypomineralized waters and contacts with the community of Lachemilla diplophylla-Lilaeopsis macloviana towards the margins (De la Barra 2003). In the dry Orotropical region in Chile the association Myriophyllum aquaticum-Potamogeton filiformis (Luebert & Gajardo 2005) has been described.

Ruppia filifolia community Table 2, col. 10 This community grows in permanent, mineralized waters (by bicarbonates and sulphates) of shallow lakes. Dry-semiarid xeric orotropical to mesotropical. Mainly on the shores of the extensive salt-marshes of the Altiplano but also in the lakes of inter-Andean dry valleys of Cochabamba.

Ranunculus cymbalaria-Zannichellia andina community (incl. Ranunculus cymbalaria-Crassula venezuelensis community De la Barra 2003) Table 2, col. 11 This water-plant community is floristically characterized by the combination of Ranunculus cymbalaria and Zannichellia andina. It grows on mineralized to somewhat saline waters. Altiplano. Dry to semi-arid xeric orotropical.

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Zannichellia andina-Potamogeton aff. striatus community (= Zannichellia andina-Potamogeton cf. pusillus community G. Navarro in G. Navarro & Maldonado 2002) Table 2, col. 12 Aquatic community characterized by the floristic combination of Zannichellia andina and the Punean element Potamogeton aff. striatus growing in mineralized and permanent waters. It gives way on shallow waters to the R an un cu lu s c ym ba la ri a- Za nn ic he ll ia an di na community (De la Barra 2003). Lakes in the eastern ranges (Vacas Basin) and in the Altiplano. Subhumid pluviseasonal supratropical and dry-semiarid xeric orotropical.

Zannichellia andina-Potamogeton pectinatus community Table 2, col. 13 Hydrophytic community characterized by the association of Zannichellia andina and Potamogeton pectinatus. This community can be considered as a geovicariant of the latter in the valley areas with a dryer and warmer bioclimate. Lakes of the dry inter-Andean valleys of Cochabamba. Drysemiarid xeric mesotropical. Dry inter-Andean valleys.

Triglochin palustris-Lilaeopsis macloviana community (= Lilaeopsio maclovianae-Triglochinetum palustris G. Navarro in G. Navarro & Maldonado 2002) Table 2, col. 14 Small helophyte swards characterized by Triglochin palustris and Lilaeopsis macloviana growing on pools and dykes in the Altiplano salt marshes and saline lakes with hypohaline and shallow waters. Dry xeric orotropical.

Altiplano.

Marsilea cf. ancylopoda community Table 2, col. 15 Monospecific community growing on shallow margins, mainly clayey of permanent or seasonal water bodies with mineralized, calcium-rich waters.

Xeric mesotropical. Inter-Andean dry valleys of Cochabamba.

Pistia stratiotes-Eichhornia crassipes community (= Eichhornietum crassipedis Samek & Moncada 1971) Table 2, col. 16 Free-floating macrophytes which are able to root in the substrate in the drought period. The typical floristic combination is between Pistia stratiotes and Eichhornia crassipes. This community grows on nutrient-rich, mineralized waters, and has its optimum in the thermotropical belt on eutrophic waters. In the study area it reaches the xeric mesotropical belt in the lakes of inter-Andean dry valleys. Other references on Eichhornia crassipes communities have been made in neighbouring countries (Gala´n de Mera & Navarro 1992, Gala´n de Mera 1995).

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Scirpus tatora community (= Scirpetum tatorae Gala´n de Mera 1995) Table 2, col. 17 Swamps of helophytes dominated by Scirpus tatora which grow on fine substrates permanently or almost permanently submerged. This habitat has a great capacity of retention and fixation of the anaerobic sediments of the wetland margins. “Totora” swamps without Typha domingensis are widespread in the Altiplano lakes (Titicaca, Uru-Uru, Poopo´) and also in the high-Andean lakes of the central north-western ranges in Cochabamba and La Paz (Navarro 2002). However, “totora” swamps with Typha domingensis are found in the dry inter-Andean valleys lower than 3,000 meters.

Dry xeric and subhumid pluviseasonal orotropical, dry-semiarid xeric mesotropical.

4.

Conclusions

As a result of the analysis of classification of the Andean aquatic vegetation in central Bolivia and the environmental factors influencing their distribution we draw the following conclusions: a) On a local scale (hydrosere level), water table depth plays a major role in floristic composition and zonation of plant communities. The most important step in the hydroseres differentiates permanent aquatic habitats from those subjected to fluctuating water table influence. Deyeuxia or Scirpus tatora swamps play this role in tropical mountain climates. b) On a regional scale and according to numerical analyses, two main groups of water plant communities were identified: one from orotropical wetlands with non-mineralized waters and the other from oro- to mesotropical wetlands with mineralized waters. Thus, vascular aquatic plant communities are primarily grouped by bioclimate and by the physicochemical characteristics of the water. c) 14 plant community types are currently recognized in the central Bolivian Andes. They are well characterized from a floristic and ecological viewpoint. As the results suggest, water-plant flora and vegetation can be useful as biological indicators of the physical-chemistry of water. These models can also be used as a preliminary step towards elucidating the vegetation diversity in the central Andes, as well as for further studies comparing other Andean areas.

References Acosta, F., Cadima, M. & Maldonado, M. (2003): Patrones espaciales de la comunidad plancto´nica lacustre en un gradiente geofı´sico y bioclima´tico en Bolivia. Ð Rev. Bol. Ecol. 13: 31Ð53.

Bragazza, L. (1999): Spatial patterns of plant species in a poor mire on the Southern Alps (Italy). Ð Plant Biosyst. 133(1): 83Ð92.

Brako L. & J. L. Zarucchi. 1993. Catalogue of the Flowering Plants and Gymnosperms of Peru/Cata´logo de las angiospermas y gimnospermas del Peru´. Monogr. Syst. Bot. Missouri Bot. Gard. 45: 1Ð1286.

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767

Braun-Blanquet, J. (1979): Fitosociologı´a. Bases para el estudio de las comunidades vegetales. Ediciones Blume, Madrid.

Casanova, M.T. & Brock, M.A. (2000): How do depth, duration and frequency of flooding influence the establishment of wetland plant communities? Ð Plant Ecol. 147: 237Ð 250.

De la Barra N. (2003): Ecological classification of aquatic vegetation of lacustrine system in Bolivia. Ð Rev. Bol. Ecol. 13: 65Ð93.

FAO (1977): Guı´a para la descripcio´n de perfiles de suelo FAO/UNESCO, Roma.

Gacia, E., Ballesteros, E., Camarero, Ll., Delgado, O., Palau, A., Riera, J. Ll. & Catalan J. (1994): Macrophytes from the Easter Pyrenean lakes: composition and ordination in relation to environmental factors. Freshw. Biol. 32: 73Ð81.

Gala´n de Mera, A. (1995): Ensayo sintaxono´mco sobre las comunidades vegetales acua´ticas del Peru´. Arnaldoa 3(1): 51Ð58.

Gala´n de Mera, A. & Navarro G. (1992): Comunidades vegetales acua´ticas del Paraguay occidental. Arnaldoa 17(1): 35Ð46.

Gala´n de Mera, A, Ca´ceres, C & Gonza´lez, A. (2003): La vegetacio´n de la alta montan˜a andina del sur del Peru´. Ð Acta Botanica Malacitana 28: 121Ð147.

Ge´hu, J. M. & Rivas-Martı´nez, S. (1982): Notions fondamentales de Phytosociologie. Ber. Internat. Symp. IVVS, Ð Syntaxonomie:1Ð33. J. Cramer ed.

Groombridge, B. & Jenkins, M. (1998): Freshwater Biodiversity: a preliminary global assessment. WCMC Ð World Conservation Press, Cambridge, UK. vii + 104 pp + 14 Maps.

Gutte, P. 1980. Beitrag zur Kenntnis zentralperuanischer Pflanzengesellschaften II. Die hochandinen Moore und ihre Kontakgesellschaften. Feddes Repert. 91(5Ð6): 327Ð336.

Hartog, C. Den & Segal S. (1964): A new classification of the water-plant communities.

Acta Bot. Neerl. 13: 367Ð393.

Kubiena, W. L. (1952): Claves sistema´ticas de suelos. CSIC, Madrid.

Liberman, M., Pedrotti, F. & Venanzoni, R. (1988): Le asociazoni della classe Lemnetea del lago Titicaca (Bolivia). Ð Hidrobiol. 2(2Ð3): 377Ð388. Ð (1991): La vegetacio´n flotante de la clase Lemnetea del lago Uru-Uru, depto. De Oruro (Bolivia). Ð Ecologı´a en Bolivia 17: 47Ð51.

Luebert, F. & Gajardo, R. (2005): Vegetacio´n altoandina de Parinacota (norte de Chile) y una sinopsis de la vegetacio´n de la Puna meridional. Phytocoenologia 35(1): 79Ð128.

Maldonado, M. (2002): Hidroecoregiones y ambientes acua´ticos. Ð In: G. Navarro & M. Maldonado: Geografı´a ecolo´gica de Bolivia, pp. 501Ð701. Fundacio´n Simo´n I. Patin˜o, Cochabamba.

Malmer, N. (1986): Vegetational gradients in relation to environmental conditions in northwestern European mires. Ð Can. J. Bot. 64: 375Ð383.

Miserere, L., Montacchini, F. & Buffa, G. (2003): Ecology of some mire and bog plant communities in the Western Italian Alps. Ð J. Limnol. 62(1): 88Ð96.

Navarro, G. (2002): Vegetacio´n y unidades biogeogra´ficas. Ð In: G. Navarro & M. Maldonado: Geografı´a ecolo´gica de Bolivia, pp. 1Ð500. Fundacio´n Simo´n I. Patin˜o, Cochabamba.

Podani, J. (2001): Syn-Tax. 2000. Computer Program for Data Analysis in Ecology and Systematics. User‘s Manual.

Rivas-Martı´nez, S. & Tovar, O. (1982): Vegetatio Andinae I. Datos sobre las comunidades vegetales altoandinas de los Andes centrales del Peru´. Ð Lazaroa 4: 167Ð187.

Rivas-Martı´nez, S., Sanchez-Mata, D. & Costa, M. (1999): North American Boreal and Western Temperate Forest Vegetation. Ð Itinera Geobot. 12: 5Ð316.

768

J. A. Molina et al.

Ruthsatz, B. (1995): Vegetation und Ökologie tropischer Hochgebirgsmoore in den Anden Nordchiles. Ð Phytocoenologia 25: 185Ð234. ´ lvarez, M. (2003): Macro´fitos como bioindicadores: una San Martı´n, C., Ramı´rez, C., A propuesta metodolo´gica para caracterizar ambientes dulciacuı´colas. Rev. Geograf. Valparaı´so 34: 243Ð253.

Seibert, P. & Menhofer, X. (1991): Die Vegetation des Wohngebietes der Kallawaya und des Hochlandes von Ulla-Ulla in den bolivianischen Anden. Teil I. Ð Phytocoenologia 20(2): 145Ð276. Ð Ð (1992): Die Vegetation des Wohngebietes der Kallawaya und des Hochlandes von Ulla-Ulla in den bolivianischen Anden. Teil II. Ð Phytocoenologia 20(3): 289Ð438.

Smolders, A. J. P., Lucassen, E. C. H. E. T. & Roelofs, J. G. M. (2002): The isoetid environment: biogeochemistry and threats. Ð Aquat. Bot. 73: 325Ð350. ter Braak, C. J. F. & Smilauer, P. (1998) CANOCO Reference Manual and User’s Guide to Canoco for Windows: Software for Canonical Community Ordination (version 4). Ð Microcomputer Power, Ithaca, NY USA, 352 pp. ter Braak, C. J. F. & Verdonschot, P. F. M. (1995): Canonical correspondence analysis and related multivariate methods in aquatic ecology. Ð Aquatic Sciences 57(3), 255Ð289.

Terneus, E. (2002): Comunidades de plantas acua´ticas en lagunas de los pa´ramos del norte y sur del Ecuador. Ð Caldasia 24(2): 379Ð391. van der Maarel, E. (1979): Transformation of cover-abundance values in phytosociology and its effects on community similarity. Ð Vegetatio 39(2): 97Ð114. van der Valk, A. G. & Davis, C. B. (1978): The role of seed banks in the vegetation dynamics of prairie glacial marshes. Ð Ecology 59: 322Ð335.

Addresses of the authors: Dr. Jose´ Antonio Molina* & Ana Lumbreras, Departamento de Biologı´a Vegetal II, Facultad de Farmacia, Universidad Complutense de Madrid, Pza. Ramo´n y Cajal s/n, 28040-Madrid (Spain).

Dr. Gonzalo Navarro,Cochabamba, Bolivia; E-mail: gonzalonavarrosanchez@gmail. com.

Nelly De La Barra, Unidad de Limnologı´a y Recursos Acua´ticos. Facultad de Ciencias y Tecnologı´a, Universidad Mayor de San Simo´n, Cochabamba, Bolivia. *Corresponding author, e-mail: jamabril@farm.ucm.es