Above-ground biomass and high temperatures are more important than productivity for the spatial pattern of bird richness in Subtropical Dry forests of Argentina

Abstract

The different ways in which biodiversity is distributed on Earth have always intrigued ecologists, promoting constant research to elucidate the causes and mechanisms that guide their spatial patterns. Numerous hypotheses have been proposed to explain biodiversity across the world. In South American Subtropical Dry forests, a global deforestation hotspot, this type of research remains poorly explored. We aimed to evaluate the response of forests bird communities to different biophysical and environmental factors analyzed simultaneously under three major hypotheses in ecology. Generalized linear mixed models (GLMMs) were used to analyze the seasonal richness and relative frequency in birds for 27 forest sites scattered through the Dry Chaco, Argentina, under the influence of the following predictors: (a) mean seasonal temperature, (b) forest biomass, (c) forest primary productivity using the NDVI (Normalized Difference Vegetation Index) and (d) landscape heterogeneity. Our results indicate that forest sites with high biomass and temperature values and with low landscape heterogeneity hold higher bird richness, without any influence of forest productivity. The relative frequency was higher in areas with high temperatures and high landscape heterogeneity around, although with low values of forest productivity. Overall, we highlight that the spatial pattern of bird communities in the Argentinean Dry Chaco forests is determined by areas with high biomass, high temperatures and mainly low landscape transformation in the surroundings. These associations must be considered in future decisions on land use for better territory planning and the conservation of these important areas for bird diversity.