Tree litter, microbes and nitrogen: a triangular approach to understanding plant-soil interactions

AMY T. AUSTIN; VIVANCO, LUCIA

Simposio; 32nd New Phytologist Symposium: Plant interactions with other organisms: molecules, ecology and evolution; 2013

Microorganisms regulate central ecosystem processes such as litter decomposition, but the nature and magnitude of plant?soil feedbacks and their interaction with global change in natural ecosystems are elusive. By using unpolluted pristine forests in Patagonia, Argentina, our group is focused on understanding the relative importance of tree species identity, resource availability and microbial composition on key ecosystem processes. We have demonstrated that plant species and N addition affected microbial functioning, with a clear home-field advantage for litter decomposition in its origin, and strong N stimulation of litter decomposition. These findings contrast with studies from polluted Northern Hemisphere ecosystems, and highlight the importance of using undisturbed ecosystems for evaluation of potential human impact. Current work on pyrosequenced bacterial and fungal microbial communities in the litter of the forest floor demonstrates that plant species affected the composition of bacterial and fungal communities even at the level of phylum. In addition, N addition consistently reduced bacterial and fungal richness, and this reduction was dependent on the identity of the plant species. Our results suggest that long-term plant?soil interactions can modulate the composition of microbial communities, and could explain the observed home-field advantage for litter decomposition. In contrast, disruption of these interactions with N addition altered microbial communities with important consequences for plant?soil interactions.