Peeking into the black box: The structure and function of soil microbial communities in response to increasing nitrogen availability

Soil microbial communities are enormously important in the cycling of nitrogen (N). Soil microbial communities may be changing due to increasing atmospheric N deposition, which in turn may have serious consequences for terrestrial storage and cycling of N and carbon (C). This work seeks to understand how the soil microbial community responds to changes in N availability and how microbial community changes translate in to changes in ecosystem functions related to N and C storage and cycling. In the first experiment, I used a phospholipid fatty acid (PLFA) approach to examine how the general soil microbial community and how specific components of the microbial community respond to increases in inorganic and organic N availability. In the second study, I focus on how the community structure of ectomycorrhizal fungi varies over an atmospheric N deposition gradient and how changes in the ectomycorrhizal fungal community relate to changes in ecosystem functions associated with N cycling such as lignin depolymerization, proteolytic activity, and N mineralization. In the third study, I conducted an N addition experiment in Maine, the point along the northeastern N deposition gradient in the United States receiving the lowest amounts of ambient N, in order to examine the role of N in producing the patterns observed in the gradient study. In the final experiment, I examined the response of fungal hyphae in situ to inorganic N fertilization which gives us insight into how ectomycorrhizal communities respond to increasing atmospheric N deposition