This project will relate nutrient cycling to long term productivity of agroecosystems by comparing nutrient cycles that prevail under agricultural methods in ancient and complex Chinese agroecosystems with those of conventional farms. With nitrogen often being the limiting nutrient in such systems, nitrogen (N) - cycling is the main focus of the study, with other nutrient cycles to be also characterized where useful. N-cycling patterns are to be modeled from annual N-transfer budgets of village-scale agroecosystems. Food web and trophic chain models of N-cycling will be compared for their ability to differentiate agroecosystem behaviors, and various calculations will be assessed for their suitability in quantifying nutrient cycling. A nitrogen-recycling-efficiency index will be derived from N-cycling measures combined with input/output efficiency criteria and soil N pool size. This index will be related to ecological sustainability using as a benchmark Chinese agroecosystems that have sustained high yields for centuries. The contemporary importance of legume cultivation to sustained agroecosystem productivity will then be evaluated using the N- recycling index. %%% Traditional Chinese agroecosystems and the eco-farms derived from them are striking examples of environmental management based upon ecological principles. Nutrient cycling patterns of such systems provide an excellent contrast to Chinese farms that use only conventional chemical nutrient management. All three agroecosystem types (traditional, eco-farm, conventional) may be found in the same bioclimatic area of China; the combination of all three types in a comparative study constitutes a unique opportunity to develop measurements of sustainability.
