PhD ceremony Ms. C.X. Garzón López: Determinants of the spatial distribution of tree species in a neotropical forest

PhD ceremony: Ms. C.X. Garzón López, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Determinants of the spatial distribution of tree species in a neotropical forest

Promotor(s): prof. H. Olff, prof. S. Bohlman

Faculty: Mathematics and Natural Sciences

In her thesis, Carol Garzón López quantified the landscape distribution of six species of tropical forest trees and evaluated the relative importance of environmental variables (part of the deterministic processes) and seed limitation (part of the stochastic processes) in determining tree spatial distributions. The mechanisms controlling species spatial distribution are divided in two extremes: deterministic (species specific adaptation to environmental conditions) and stochastic (dispersal limitation and stochastic demography). There are several studies looking at these two mechanisms but the outcomes vary greatly due to the lack of explicit consideration of a critical component: spatial scale. Previous studies aiming to unravel stochastic and deterministic processes in tropical forests are often contradictory, leading to potential underestimation of the importance of deterministic/stochastic processes.

Garzón López used remote sensing techniques in combination with field experiments to link seed limitation and establishment limitation, in order to estimate the relative importance of stochastic and deterministic processes in determining species recruitment at the early stages. The study provided three important findings: i) the spatial scale has a critical effect on habitat association studies, ii) seed predation depend on conspecific and heterospecific plant species densities, iii) seed and establishment limitation control the spatial distribution during the early recruitment stages. These findings suggest that the relative importance of stochastic and deterministic processes that control species distribution depend on the scale of the study and ecological factors that continuously change in time and space.