| 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. |
