Geographical situation:

The study area El Bosque La Carbonera - San Eusebio is a montane cloud forest in the Venezuelan Andes, approximately 40 km air distance northwest of Mérida. Elevation above sea level is between 2200-2500 m; mean annual temperature is 12.6 °C and mean annual precipitation does not exceed 1500 mm, but with daily cloud and mist entry.

The forest has been in possession of the University of the Andes (ULA), Instituto de Silvicultura de la Facultad de Ciencias Forestales, for the last 50 years. The 370 ha forest consists mainly of primary vegetation, but includes an area of about 120 ha secondary vegetation: relics of primary forest where some selective logging has taken place and some abandoned tree plantations of Cedrela montana Moritz ex Turcz. (Meliaceae) are situated. In the primary forest the emergent tree Decussocarpus rospigliosii (Pilger) de Laub. (Podocarpaceae) is dominant (see Figure below).

The plots were established in primary forest (a triangle of approximately 0.1 ha with four emergent D. rospigliosii and 66 subcanopy and understory trees), and in secondary and disturbed vegetation at four representatively selected locations:

1. A plot in a relic forest with one emergent relic tree (D. rospigliosii).
2. A transect along the dirt road through secondary and disturbed forest.
3. A tree plantation of Cedrela montana comprising approximately 400 trees.
4. A sector of a former clear cutting, which was completely cleared for a biomass determination 26 years ago and left undisturbed since then.

Epiphytes were sampled following the single rope technique of mountaineering climbing. In primary forest reiterated access to the canopy was provided by installing a permanent rope system, connecting three emerging phorophytes in a triangle with transversal ropes (see figure left below). Reaching all the tree crowns within the triangle was possible by lowering down from the transversal ropes. Here epiphyte individuals of 60 trees (DBH > 5 cm) were completely registered and measured (in total 4121 individuals).

View at the primary forest at La Carbonera. In front the former clear cutting (study site IV.). Photo: S. Engwald.

Presentation of canopy access in the primary forest of La Carbonera: 1. Climbing up an emergent D. rospigliosii-tree. 2. A traversal rope (position can be changed by means of shunts) is fixed at the rope-triangle between three emergent trees. 3. The climber reaches even the outer canopy of smaller trees. Engwald 1999.

Viviane Schmit-Neuerburg ascends a non-eleastic rope, normally used by speleologists. She is demonstrating the single rope technique equipped with harness, Yumar-ascenders, clips, metal loops, and safety cords. Photo: S.Engwald

Before climbing Stefan Engwald shoots a thin fishing line over a thick and trustworthy branch. Then the climbing rope can be pulled up. Photo: V. Schmit-Neuerburg.

66 vascular epiphyte species and more than 1000 epiphytic individuals were found by S. Engwald in the crown of a sampled Decussocarpus-tree. Photo: J. Szarzynski.

Scientists move from tree to tree hanging in a strong pulley, which is connected to their harness. Photo left: S. Engwald; Photo right: J. Szarzynski.

Organization:
Our works took place in close cooperation with the Centro Jardín Botánico (Facultad de Ciencias) of the Universidad de Los Andes (Mérida) and their directors Prof. Dr. M. Ricardi and Dr. J. Gaviria. Yelitza León from the Centro Jardín Botánico studied the epiphytic bryophyte flora of La Carbonera for her PhD.-thesis under the direction of Prof. Dr. J.-P. Frahm from the University of Bonn. Living plants were collected for further cultivation in the Botanical Garden of the Centro Jardín Botánico. Vouchers were deposited at the Herbarium of the Centro Jardín Botánico (MERC), with duplicates at the "Herbario Nacional de Venezuela" (VEN).

Scientific aim:
Our studies should elucidate the structural and ecological conditions that determine the spatial distribution of epiphytes within the canopy of the primary forest. Therefore various parameters were analyzed: forest stand and tree architecture, stand climate as well as microclimate of an selected host tree (especially light environment), substrate quality (structural and chemical properties of branches, but also of canopy substrate). Ecological requirements of some frequent epiphyte species were determined and statistically proved. Diversity and floristic characters (species composition, alpha- and beta-diversity indices, species-area-curves etc.) were described in order to detect specific patterns of epiphyte diversity in mountain rain forest.

Another aim comprises the comparison of epiphytic plant communities in a primary cloud forest and neighbouring areas of secondary vegetation, contributing to the still very incomplete knowledge of the effects of anthropogenic alterations to one of the most important structural elements of tropical vegetation, the epiphytes. The bioindicative qualities of vascular epiphytes should be tested.

Publications

• Barthlott, W., Schmit-Neuerburg, V., Engwald, S. & J. Nieder, 2001: Diversity and abundance of vascular epiphytes in secondary vegetation: a case study in a montane rain forest of the Venezuelan Andes. - J. Plant Ecology 152 (2): 145-156.
• Engwald, S., 1999: Diversität und Ökologie der Epiphyten eines Berg- und eines Tieflandregenwaldes in Venezuela.- Dissertation. Hamburg, Libri-BoD: 390 pp.
• Engwald, S., Schmit-Neuerburg, V. & W. Barthlott, 2000: Epiphytes in rain forests of Venezuela - diversity and dynamics of a biocenosis.- in Breckle, S.W., Schweizer, B. & U. Arndt (Eds.): Results of worldwide ecological studies. Proceedings of the 1st Symposium by the A.F.W Schimper-Foundation - from H. and E. Walter - Hoheneim, Oktober 1998.- Stuttgart-Hohenheim, Verlag Günter Heimbach (ISBN 3-9805730-2-8): 425-434.
• Nieder, J., Engwald, S. & W. Barthlott, 1999: Patterns of neotropical epiphyte diversity.- Selbyana 20 (1): 66-75.
• León-Vargas, Y., Engwald, S. & M.C.F. Proctor, 2006: Microclimate, light adaptation and desiccation tolerance of epiphytic bryophytes in two Venezuelan cloud forests.- Journal of Biogeography 33: 901-913.