9700737 D'Antonio This proposal examines the links between biological invasions, changes in community composition, and alteration of ecosystem processes that contribute to changes in the global nitrogen (N) cycle. The objectives of the proposed research are to define mechanisms by which non-indigenous grasses in Hawaiian seasonal submontane woodlands have altered ecosystem N cycling and how these changes affect N availability to plant growth and ecosystem N accumulation. The hypothesis that insertion of grasses increases rates of N cycling and decreases rates of loss will be tested by comparing N dynamics among unburned woodland with grasses removed, unburned woodland with grasses, and burned sites that are grass dominated. Measurements of mineral nitrification, soil trace gas emissions, plant production, and ecosystem N partitioning using an 15N tracer will be made. This research provides a unique link between community and ecosystem processes by addressing the role that a new growth form plays in ecosystem N dynamics. This research will differentiate mechanisms through which grasses effect N dynamics, and it will simultaneously compare the physical, chemical, and competitive effects of a growth form on nutrient dynamics. This research also addresses feedbacks between growth form of invading species and local rates of resource supply that may influence competitive interactions and ultimately, the success of the invaders.
