Large mammalian herbivores modulate plant life-form diversity in tropical forests

Author(s)

Yuri Silva de Souza

• Document type: Master's Dissertation
• Press: Rio Claro. 2021-03-22.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro
• Defense date: 2021-03-12
• Advisor: Mauro Galetti Rodrigues

Abstract

The world’s terrestrial biomes are broadly classified according to the dominant plant-life forms that define ecosystem structure and processes. Although the abundance and distribution of different plant life-forms can be strongly determined by factors as climate and soil composition, large mammalian herbivores have a strong impact on plant communities, thus defaunation (the local or functional extinction of large animals) has the potential to alter the compositional structure of plant life-forms in natural ecosystems. Tropical rainforests sustain a high diversity of life-forms, including trees, palms, lianas, shrubs, herbs, and bamboos, all of which play important ecosystem functions. Here, we experimentally evaluate how large mammalian herbivores affect the dominance, diversity, and coexistence of these major tropical forest plant life-forms in a long-term replicated exclusion experiment in the Atlantic Forest of Brazil. Over the course of 10 years large herbivore exclusion decreased life-form diversity, increased the absolute abundance of palms and trees (22% and 38%, respectively), and increased the diversity of species within these two groups, in the detriment of other life-forms. Furthermore, all pairwise relationships between life-forms were positive on plots where herbivores had access, whereas several strong negative relationships emerged in plots where herbivores were excluded. This occurred despite strong background directional temporal trends affecting plant communities in both experimental treatments across the region. Our work indicates that defaunation alters life-form dominance and erodes life-form diversity and coexistence and hence might lead to profound impacts on important ecosystem functions and a vertical and horizontal structural simplification of tropical rainforests (AU)

• FAPESP's process: 19/05538-5 - Influence of defaunation on the dynamics of tropical plant life forms
• Grantee: Yuri Silva de Souza
• Support Opportunities: Scholarships in Brazil - Master