典型草原植物水分利用效率和养分利用效率的联动关系研究：以稳定性碳、氧同位素为技术手段

How to scientifically regulate the water use efficiency (WUE) and nutrient use efficiency (NUE) of grassland plants is a very important scientific issue for global change study. Co-movement relationships between WUE and NUE occur in grassland plants, which may affect grassland primary productivity. However, there are very few studies on the co-movement relationships between WUE and NUE, the change of co-movement with changing precipitation and increasing nitrogen deposition and the underlying mechanisms, the relationship between the change of co-movement and primary productivity. Using stable carbon and oxygen isotope techniques and an established field manipulation experiment of precipitation change and nutrient addition, this study attempts to demonstrate the co-movement relationships between WUE and NUE on the two scales of leaf and community in the Inner Mongolia typical grassland, examine their responses to precipitation change and nitrogen deposition and explore the underlying mechanisms. The main objectives are: 1) the effect of increasing precipitation, decreasing precipitation and adding nitrogen on the co-movement relationships between WUE and NUE; 2) the determinant factors of WUE change and their impacts on NUE under various water and nitrogen conditions; 3) the relationship between the change of the co-movement relationship between WUE and NUE and primary productivity. This study will enhance our knowledge on the water and nutrient use strategy in grassland ecosystems as well as provide a theoretical basis for the scientific management of water and fertilizer conditions to promote primary productivity in the Inner Mongolia grassland ecosystems.

如何科学调控草原植物水分利用效率（WUE）和养分利用效率（NUE）以促进初级生产力是当前全球变化研究的热点问题。草原植物WUE和NUE之间存在联动关系，可能影响初级生产力。但关于两者之间联动关系的表现，联动关系随降水改变和氮沉降增加的转变及其机理，联动关系转变与初级生产力的关系等的研究甚少。本项目以内蒙古典型草原为研究对象，利用已建立的降水改变和氮沉降实验平台，采用稳定性碳、氧同位素技术手段，在叶片和群落两个尺度上揭示WUE和NUE联动关系对增加降雨、减少降雨和氮沉降的响应及其机理。重点研究：1）增雨、减雨和氮添加对典型草原WUE和NUE联动关系的影响；2）水氮环境改变下，决定WUE变化的影响因素及其对NUE的影响；3）WUE和NUE联动关系转变与初级生产力的关系。研究结果不仅能够深化对草原生态系统水分和养分利用的认识，还将为科学管理内蒙古草地生态系统水肥条件、促进初级生产力提供理论依据。

本项目以内蒙古典型草原为研究对象，利用降水改变和氮沉降实验平台，采用稳定性碳、氧同位素技术手段，揭示了WUE和NUE联动关系对增加降雨、减少降雨和氮沉降的响应及其机理。重点研究了：1）增雨、减雨和氮添加对典型草原WUE和NUE联动关系的影响；2）水氮环境改变下，决定WUE变化的影响因素及其对NUE的影响；3）WUE和NUE联动关系转变与初级生产力的关系。研究结果表明，草原优势物种在WUE 和NUE之间存在明显的联动关系。降雨和土壤可利用养分对联动关系的影响控制着草地植物生产力的变化。本研究深化了草原生态系统水分和养分利用的认识，为科学管理内蒙古草地生态系统水肥条件、促进初级生产力提供理论依据。