PRF/J: Nutrient Cycling as a Measure of Agroecosystem Sustainability

该项目将通过比较古代和复杂的中国农业生态系统中以农业方法为主的营养循环与传统农场的营养循环，将营养循环与农业生态系统的长期生产力联系起来。由于氮通常是这些系统中的限制性养分，氮(N)循环是研究的主要焦点，其他营养循环也将在有用的地方进行表征。氮循环模式将根据村庄尺度农业生态系统的年度氮转移预算进行建模。将比较食物网和营养链模型区分农业生态系统行为的能力，并评估各种计算方法在量化养分循环方面的适用性。将氮循环措施与投入/产出效率标准和土壤氮库大小相结合，得出氮循环效率指数。该指数将与生态可持续性有关，作为中国农业生态系统的基准，几个世纪以来一直保持高产。豆科作物种植对维持农业生态系统生产力的当代重要性将利用氮循环指数进行评估。中国传统的农业生态系统及其衍生的生态农场是基于生态原则的环境管理的突出例子。这种系统的养分循环模式与只使用传统化学养分管理的中国农场形成了极好的对比。三种农业生态系统类型（传统、生态农场、传统）在中国同一生物气候区均存在；在比较研究中，所有三种类型的结合构成了发展可持续性测量的独特机会。

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.