Short- and long-term impacts of an introduced large herbivore (Buffalo, Bubalus bubalis L.) on a neotropical seasonal forest

Abstract

Herbivory of large mammals is a key factor influencing plant communities, with effects on plant growth, survival and reproduction. These effects may be more pronounced when the herbivores are exotic ungulates. We evaluated the impacts of buffaloes (density of 1 individual per hectare) on sapling and shrub assemblages in a semideciduous seasonal forest in southern Brazil. We also investigated whether these impacts could affect the long-term maintenance of forest communities. To address these points, we used two distinct approaches in fragments of seasonal forests located in buffalo farms: firstly, by establishing a buffalo-exclusion experiment (over 14 months), and secondly, by comparing areas with three different histories of buffalo occurrence (protected from buffalo encroachment for 3 and 10 years and freely accessed by buffalo). In both approaches, we evaluated the following ecological attributes: plant cover, richness, diversity (Shannon index), biomass and average height. The results of the exclusion experiment did not indicate any significant effect of buffalo exclusion for the evaluated ecological attributes. On the other hand, species composition differed between communities when comparing buffalo presence versus 10 years of buffalo exclusion. Moreover, richness increased and average height decreased after this 10-year period. We also detected an increase in diversity and a retraction of soil compaction, after 10 years of exclusion. We conclude that forest patches do not show short-term responses to buffalo removal. Nevertheless, in the long-term absence of large herbivores, the forest tends to develop in complexity by increasing in species richness.