Phytocoenologia, 39 (1), 109–156 Berlin – Stuttgart, April 21, 2009
The forest vegetation of Ramal de Guaramacal in the Venezuelan Andes by Nidia L. CUELLO A, Guanare, Venezuela and Antoine M. CLEEF, Amsterdam, The Netherlands with 12 figures, 9 photographs, 5 tables and 3 appendices Abstract. Montane forest community composition of Ramal de Guaramacal, Venezuelan Andes, was studied along the altitudinal gradient on both sides of the range with different slope expositions. Thirty five 0.1 ha plots were surveyed, with variable intervals of 30 to 150 meters between 1350 m and 2890 m and nine plots of variable size (50 m2 to 400 m2) were surveyed in dwarf forests located between 2800–3050 m. A total of 388 morphospecies with dbh ≥ 2.5 cm, corresponding to 189 genera and 78 families of vascular plants, were recorded from a total of 45 forest plots. The TWINSPAN phytosociological classification, based on both floristic composition and species relative abundance, revealed seven forest communities at association level, grouped in three alliances and one montane forest order group. Three subandean forest (LMRF) communities and four Andean – high Andean forest (UMRF-SARF) communities are distinguished and described according to the Zürich-Montpellier method. The Geo nomo undatae–Posoquerion c o ri a c e a e alliance contains two subandean forest communities (S i m ir o ery throxyli–Quararibeetum magn i f i c a e and C o n c h o c a rp o l a re n si s– C o u ssa re e t u m m o ri t z i a na e ); the Farameo killipii–Prunion mori t z i a n a e alliance contains one subandean forest community (C ro i z a t io b revipetiolatae–Wettinietum praem o rsa e ) and one Andean forest community (S c h e f f l e ro f e rru g i n e a e – Cy bianthetum laurifolii) and the R u i l o p e z i o p a l t o n i o i d e s– C y b i a n t h i o n m a rg i n a t i i alliance includes one Andean (Geissantho andini–Mico n i e t u m j a h n i i ) and two high Andean forest communities (G a u l t he r io anastomosantis–Hesperomeletum ob t u si f o l i a e and the Li b a n o t h a m n e t u m g ri f f i n i i ). Altitudinal zonation, forest floristic diversity, composition and forest structure is discussed between slopes and along the altitudinal gradient and compared, where possible, to other montane forests. In LMRF, Rubiaceae, Lauraceae and Melastomataceae are the most speciose of woody families. In UMRF, the Lauraceae family is still the most diverse, followed by Melastomataceae and Myrtaceae, while in SARF the Asteraceae and Ericaceae are the most species rich families. The structure of the montane forests of Ramal de Guaramacal becomes more compressed towards higher elevations. LMRF are dense and of medium height, with canopies up to 25 m tall, while UMRF canopies can reach up to 18 m, and those of SARF are only 6–8 (10) m tall. Basal area was slightly increased on the North than on the South slopes and shows different patterns against altitude between slopes. More diversity and density of palms, lianas and climbers is clearly observed in LMRF, but richness of liana species is also important in SARF forests. Forest altitudinal zonation is variable between the North and South slopes of Guaramacal, with the forest zones of UMRF on the windward South slope, tending toward reaching lower elevations than on the opposite and drier North slope. There is a low altitudinal limit of the upper forest (Upper Forest Line or UFL) apparently caused by the “top effect”. eschweizerbartxxx ingenta
Keywords: floristic composition, forest structure, Lower Montane Rain forest, Upper Montane Rain Forest, Subalpine Rain Forest, phytosociological classification, altitudinal zonation, Venezuela, Andes.
Introduction Montane forests of the northern Andes are fragile ecosystems of significant biological and ecological diversity with a complex biogeographical history, and playing a major role in the regional hydrological balance (Gentry 1995, Cavalier & Goldstein 1989, Cavelier et al. 1996, Holder 2006, Kappelle & Brown 2001). Despite increased attention and conservation interest of the northern Andean forest ecosystem over the past two decades (Henderson et al. 1991, Churchill et al. 1995, Gentry 1995, Luteyn & Churchill 2000, Kappelle & Brown 2001, Van der Hammen et al. 1984), studies on montane forests of the Venezuelan Andes remain limited in area, subject and time. The majority of studies have been carried out in the montane forests of the state of Mérida. DOI: 10.1127/0340 – 269X/2009/0039 – 0109
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The silvicultural studies of La Mucuy and La Carbonera (Lamprecht 1954, Veillon 1965, 1985), vegetation ecology (Vareschi 1953, 1956, Yánez 1998); floristic analysis (Kelly et al. 1994, 2004); and several studies focusing on different aspects of ecophysiology, population ecology and hydroecology of cloud forests (Brun 1979, ICAE 2005), aspects of diversity, structure and biogeography on a succesional and mature forest stands close to the town of Mérida (Schneider et al. 2000, Schneider 2001) are particularly noteworthy. Few Andean montane forest areas outside of Mérida State have been studied (Bono 1996, Ortega et al. 1987, Cuello 1996, 1999, 2002 and Dorr et al. 2000). Beyond the Andes, other montane forest areas previously studied are Coastal Cordillera (Huber 1986, Howorth & Pendry 2006); Cerro El Avila (Vareschi 1955, Steyermark 0340 – 269X/09/0039 – 0109 $ 21.60 © 2009 Gebrüder Borntraeger, D-14129 Berlin · D-70176 Stuttgart
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