Die Tropenstation La Gamba

Die „Tropenstation La Gamba“ in Costa Rica – Wissenschaftlicher Bericht
Central America. Probable reasons are: (a) high annual precipitation without a dry season
(favouring tree diversity), (b) the well structured geomorphology with plains, hills, slopes, ridges
and gorges, (c) soil heterogeneity with different nutrient and water conditions, creating many
microhabitats which allow different guilds to survive, and (d) the dynamics of the forest, by which
different forest stages allow the whole species spectrum, from short pioneer to climax species, to
regenerate within a small area.
These ecological differences allow different forest types to develop within a small area.
This is why the four selected plots show such profound differences and have different affinities to
other forest types. Broadly speaking, however, they are more closely related to Panama and South
America than to the drier Northern forests of Central America.
Special features of the four forest plots. (1) Inland slope forest. This forest type proved to have
its closest affinities to lowland forests in the Chocó region (Colombia) and to lowland forests on
the Atlantic side of Costa Rica (e.g. La Selva). This is reflected in the abundance of palms and
hemiepiphytes, and is also reflected in parameters such as high individual-density, BA and TV.
(2) Gorge forest. This forest type was found to have typical structural features of montane forests
as found frequently in Costa Rica, with thick- but short-stemmed trees, abundance of tree ferns and
epiphytes, and the occurrence of species otherwise confined to montane forests (Billia colombiana
– Hippocastaneaceae, Perrottetia sessiliflora - Celastraceae), and the richness of toothed-leaved
species.
(3) Ridge forest. This type proved heterogeneous and included typical elements of slope forests in
its wetter section, while the drier section had elements of secondary forest with a high density of
Vochysiacae. Its structure exhibits features of Amazonian forests on poor soils in Venezuela, e.g.
extremely high individual-density, and tall but thin-stemmed trees.
(4) Coastal slope forest. This plot was found to be unusual and difficult to compare with other
areas because of its extremely tall trees, exceptionally high BAs and TVs, the rareness of palms
and the abundance of otherwise rare species and families such as Caryocar costaricensis
(Caryocaraceae), Manilkara staminodella (Sapotaceae) and Schizolobium parahyba
(Caesalpiniaceae). Similar forests were found near Palmar Norte (Costa Rica) and in the Península
de Osa, but they appear to be rare elsewhere.
Mag. Dr. Anton Weissenhofer
Univ. Vienna, Austria
Dep. of Palynology and Structural Botany
Rennweg 14 - A 1030 Vienna (Wien), Austria
Tel. 0043 1 4277 54083
Fax. 0043 1 4277 9541
anton.weissenhofer@univie.ac.at
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