氮是构成一切生命体的重要元素，但大多数陆地生态系统土壤中的可利用氮素相对于植物的生长需要往往不足，因而氮限制着陆地生态系统碳的持续积累。草海位于贵州西北部，是我国最大的天然岩溶湿地，该湿地内水生植物对稳定区域岩溶碳汇效应具有十分重要的作用，而稳定的氮源供给则是保障该湿地内生物过程利用岩溶作用产生的无机碳向有机碳持续转化的关键。本项目以草海岩溶湿地流域为研究对象，利用地球化学及稳定同位素等解析手段，揭示草海岩溶湿地生态系统氮素的时空分布规律，并阐明该湿地生态系统中氮的来源，及迁移转化过程。研究结果将是对喀斯特生态系统氮循环研究的一个重要补充，同时可进一步深化对生物参与下岩溶碳汇稳定性的认识，也为草海湿地的保护提供借鉴和指导。

Nitrogen is a major nutrient that is essential to all life on earth, but the available nitrogen in most terrestrial ecosystems is often deficient in relation to the growth of plants, and nitrogen limits the continued accumulation of carbon in terrestrial ecosystems. The Caohai wetland is located in the northwest of Guizhou province, and is the largest natural karst wetland in China, the wetland ecosystem play an important role in maintaining the stability of carbon sink effect related to carbonate rock dissolution, but the stable supply of nitrogen source is the key to ensure the sustainable use of aquatic photosynthesis through converting dissolved inorganic carbon into organic carbon. In this study, the Caohai wetland catchment has been selected as the study area, to identify the sources and transformation of inorganic and organic nitrogen in the wetland through hydrochemistry and stable isotope. The main objectives of this study are: (1) to clarify the spatial and temporal variability of nitrogen in wetland; (2) to elucidate the sources and transformation of nitrogen using stable isotopes for karstic settings; and (3) to analyze original data using statistic methods to illustrate the behavior of nitrogen in the typical karst-dominated wetland. Results will provide important information on karst-dominated wetland ecosystem response to nitrogen, the baseline data to understand the influence of biological behavior on karst carbon sink, and provide the utility for protection and remediation planning in wetland ecosystems.