Entropy Dynamics of Southeastern Longleaf Pine Ecosystems

Ecosystems are open systems that exchange matter and energy with their environment. Ecosystem structure and legacy can affect the efficiency to exchange matter. Entropy has been proposed to describe these differences as it relates energy use efficiencies of ecosystems to their thermodynamic environment (i.e., temperature gradients). We studied three sites in a longleaf pine ecosystem with varying levels of anthropogenic legacy and plant functional diversity, all of which were exposed to extreme drought. We show that structural and functional characteristics contribute to differences in energy use efficiencies at the three study sites. Our results demonstrate that ecosystem function during drought is modulated by decreased absorbed solar energy and variation in the partitioning of energy and entropy exports owing to differences in site enhanced vegetation index and/or soil water content. Slow adjustment at the anthropogenically altered site prolonged its recovery from drought by approximately 1 year. In contrast, stands with greater plant functional diversity (i.e., the ones that included both C3 and C4species) adjusted their entropy exports when faced with drought, which accelerated their recovery. Our study provides a path forward for using entropy to determine ecosystem function across different global ecosystems.

See full text at: https://bg.copernicus.org/articles/16/1845/2019/