Document Type

Thesis

Degree

Master of Science

Major

Biology, Ecology

Date of Defense

11-26-2018

Graduate Advisor

Robert E. Ricklefs, Ph.D.

Committee

Robert Marquis

Sebastian Tello

Abstract

During the last few thousand years, human population growth and resource use has been reshaping the planet’s nutrient cycles, climate and biodiversity and might be causing significant changes to spatial and temporal patterns in the distribution of species, and a general erosion of biodiversity at global scales. Many studies have been looking to model and predict how species could respond to actual rates of change on environmental conditions, with a high interest in terms of species distribution and richness with potential extinctions. However, how global change impact local communities still remains unclear. Moreover, previous research suffers from a significant bias against Tropical montane regions. In this study, we evaluate whether diversity and composition of communities in an Andean Tropical forest are changing, potentially in response to changes in environmental conditions. We analyze the dynamics in 26 forest plots that are part of a larger network of nearly 490 plots located on the eastern slopes of the Bolivian Andes. We quantify mortality and recruitment rates, document changes in diversity and compare changes in species composition to null model expectations. We have that mortality and recruitment rates occur at about 1.6% per year, and that richness seems to be increasing in regions of cold climates, but decreasing in warm regions. Finally, we find evidence that community composition is shifting across all environmental conditions. Our analyses support the idea that communities in the Tropical Andes are going through changes consistent with an effect of global change. However, the final causes for the changes we observe are yet unknown. Understanding the responses of forest communities is urgently needed to advance theory in community ecology, but also to understand and manage natural ecosystems in a changing World.

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