Variation in the density and diversity of seed rain in two neotropical rainforests (at Cocha Cashu and Los Amigos Biological Stations, southeastern Peru)
2007
Thesis
103
Swiss Federal Institute of Technology
Zurich, Switzerland
Los Amigos;Cocha Cashu;plants;trees;ecology;intermediate spatial scales;dispersal
The ecological mechanisms that maintain tree diversity in (neo)tropical rainforests are still widely discussed. One of the many factors and steps to consider is seed dispersal. Different from temperate forests up to 90% of all tree species in the tropics depend on frugivorous animals (e.g. bats, monkeys, birds) as their seed dispersers. Studies have demonstrated that seed dispersal by those animals often shows a clumped pattern, with most of the dispersed seeds carried to sleep-, roost- or feed trees or between those along travel routes. In this study it was asked if fruiting trees act as dispersal foci by testing the following three hypothesises: Higher species richness and density is found in seed rain beneath animal-dispersed trees during their fruiting period(s): I) compared to their non-fruiting period, II) compared to non-fruiting periods of conspecific trees (species groups), III) compared to non-fruiting periods of conspecifics and wind-dispersed trees (all trees). Seed rain was observed at Cocha Cashu and Los Amigos Biological Stations in the lowland rainforest of south-eastern Peru. At both sites and in all cases hypothesis I) had to be rejected. Furthermore significant higher species richness in seed rain was observed during fruiting compared to non-fruiting periods on a species-groups- or on an over-all-tree-level. The pattern in seed density also shows similarities between the two sites, indicating on an over-all-tree-level only little significance and on a species-groups-level very little or no significance for differences between the different phenology categories. These results show evidence for the role of fruiting trees as important dispersal foci in a neotropical rainforest.