Effects of atmospheric N deposition on plant-microbe interactions

Across broad spatial scales we know that the structure and function of plant and soil microbial communities influence each other. This is because the availability of growth-limiting resources shapes the composition of biotic communities. Resource availability for soil microorganisms is constrained by organic compounds in dead leaves and roots that can be used to generate cellular energy. The pool of available substrates (plant inputs) influences which microorganisms are most competitive in the soil environment and that is reflected in the soil microbial community structure, which is the assembly of organisms present in a microbial community, and the microbial community function, which is the capacity to produce enzymes that catalyze biogeochemical reactions. Microbial community structure and function feeds back to impact the availability and cycling of growth limiting nutrients, and ultimately the success of plant communities. Although this conceptual model of plant-microbe interactions is well accepted, the strength and directionality of such interactions is not well understood. To investigate such interactions, I have established six experimental plots at the Chichaqua Wildlife Area in collaboration with Stan Harpole. At these sites we will manipulate nutrient additions to alter plant productivity and resource allocation, thereby creating conditions that will likely alter the structure and function of the plant and soil microbial communities. These prairie sites are part of the Nutrient Network (NutNet), a larger network of sites designed to address questions about the general impacts of nutrient additions on ecological systems.