Die Tropenstation La Gamba

Die „Tropenstation La Gamba“ in Costa Rica – Wissenschaftlicher Bericht
LAUTSCH, D. 2000: Ferns and fern allies of the Bosque Esquinas ("Regenwald der
Österreicher"), Costa Rica. - Diploma Thesis, University of Vienna. Vienna. Faculty for
mathematical and natural science.
The study deals with the diversity and (to a minor degree) ecology of ferns and fern
allies in the Bosque Esquinas, Costa Rica. The Bosque Esquinas ("Regenwald der
Österreicher") is situated in SE Costa Rica at 8'41' N and 83'13' W, between the Golfo
Dulce (Pacific Ocean) and the Carretera Interamericana. The forest covers an area of
approx. 14 000 ha (140 km') and is part of the Corcovado National Park. According to
HOLDRIDGE's Life Zone System (HOLDRIDGE, 1967) the Esquinas forest can be
classified as a 'Tropical Wet Forest', annual rainfall is around 6500-7000 mm and
average temperature c. 27.5'C.
Collection work and field studies were carried out during a period of five
months (Feb. to April, and July to September 1999). The Biological Station La Gamba
served as base for the field work. The floristic inventory is certainly not complete, but is
thought to cover the most significant and most frequent taxa.
Specimens of 83 species out of 47 genera of Pteridophyta s. str. were collected
and identified to species. The total number of species to be expected in the Esquinas
forest is perhaps 100-120 species in around 50 genera. The group of Lyopodiophyta,
especially the genus Selaginella, needs further study and is treated here only
fragmentarily. In this group c. 15 species in three genera can be expected. Keys are
presented for identification of the ferns recorded and descriptions of the families, genera
and species are provided together with illustrations of most species.
The forest sites with the highest fern density, both in species and individual
number, were found to be the ravines. This is apparently a result of general adaptation of
ferns to wet and instable environments. Most of the species occurring in primary forest
are not restricted to it, whereas most of the species characteristic of disturbed sites and
secondary forest are not found in primary forest. The latter ferns are very important
plants in vegetation succession.
With regard vascular plants, the most significant pioneers in vegetation
succession are the following ferns: Pityrogramma calomelanos (Pteridaceae),
Dicranopteris pectinata (Gleicheniaceae) and Lycopodiella cernua
(Lycopodiaceae/Lycopodiophyta). In the subsequent step of succession, species of
Cyatheaceae become (among others) important. Cnemidaria choricarpa (Cyatheaceae)
invades wet, Metaxya rostrata (Metaxyaceae) dry sites. In secondary forest Cyathea spp.
are important treelets.
There are two key species indicating dry soil: Polybotria cervina
(Dryopteridaceae) and Lygodium venustum (Schizaeaceae). Five species can be taken as
indicative of wet soil: Nephrolepis multflora (Oleandraceae), Lonchitis hirsuta
(Dennstaedtiaceae), Thelypteris nicaraguensis (Thelypteridaceae), Tectaria
draconoptera, T plantaginea and T. incisa (Tectariaceae). Acrostichum aureum
(Pteridaceae) is the key species indicating saline soil. In the brackish 'slacks' at the Golfo
Dulce a characteristic association of Acrostichum aureum (Pteridaceae) and Nephrolepis
multiflora (Oleandraceae) and Cocos nucifera (Arecaceae) can be found.
Anschrift des Autors:
Mag. Dominik Lautsch
Inst. f. Botanik der Univ. Wien
Rennweg 14, A-1030 Wien
TEL. ++43-1-4277-54080
Fax. ++43-1-4277-9541
a9606933@unet.univie.ac.at
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