前期研究结果表明，干热河谷地区凋落物周转时间与植物氮磷以外的某些元素含量具有极大的关联，意味着这些元素可能会限制植物对土壤的养分返还。那么这些元素是否可以调节植物-土壤反馈过程，影响氮磷元素的循环，最终作用于植物C:N:P化学计量特征和生产力呢？围绕这一问题，本项目以干热河谷萨瓦纳草地中的优势植物为对象，依托野外控制实验平台，通过物种配置和元素添加处理，探讨植物体元素（特别是氮磷以外的其它元素）含量种间差异和外源元素添加对植物-土壤反馈的调控作用，确定其中的限制性元素，阐明这些元素对生态系统生产力与植物C:N:P化学计量特征时间变化的影响机制，揭示多元素耦合的生物地球化学机制。研究结果将有助于认识干热河谷生态系统碳氮磷生物地球化学循环，可在一定程度上为该地区生态系统管理提供科学支撑。

Our previous study showed that litter turnover time was significantly related to concentration of some elements beyond nitrogen and phosphorus in plants from one arid-hot valley. This indicated that these elements might limit nutrient return from plant to soil. Can availabilities of these elements affect plant C:N:P stoichiometry and productivity via regulating the process of plant-soil feedback and cycles of nitrogen and phosphorus? To answer this question,we will carry out a research in this project relying on field experimental platforms with the treatments of plant species and element addition respectively. We will focus on the dominant plants in savanna grassland from the arid-hot valley to investigate the effect of interspecific variation of plant element concentrations (especially concentrations of those elements beyond nitrogen and phosphorus) and exogenous elemental addition on regulating the process of plant-soil feedback, identifying the limited elements in biogeochemical cycles, unravelling how these elements will affect the subsequent changes of ecosystem productivity and plant C:N:P stoichiometry, revealing biogeochemical mechanism of the coupling of multiple elements. The results will enhance our understanding of the biogeochemical cycle of carbon, nitrogen and phosphorus in ecosystem from this arid-hot valley, and potentially will provide a scientific support to ecosystem management in this area.