放牧强度对温性草甸草原生态系统碳氮分配的影响

放牧是草原最主要的利用方式，明确放牧活动对草原生态系统碳氮分配及其耦合关系影响机制，是研究我国草原碳氮循环过程的关键。目前从生态系统角度考虑该方面影响机理尚不清晰且适宜模型匮乏。本项目以内蒙古羊草草甸草原为研究对象，依托呼伦贝尔草原生态系统国家野外观测站，基于控制放牧实验平台，利用长期定位观测数据和模型模拟，研究不同放牧强度下植物地上地下碳氮分配、凋落物碳氮动态、土壤及微生物垂直碳氮分配和内在联系，及其草原生态系统碳氮与植物功能群、物种多样性和土壤物理生物特性关键因子的关系，确定维持碳氮稳定性的因子及阈值；建立适用于温性草甸草原生态系统碳氮过程模型，评估和预测放牧干扰对草原生态系统碳氮平衡和碳氮分配的影响；从生态系统角度揭示草甸草原碳氮分配及其耦合关系对放牧干扰的综合响应机理。为我国草原合理利用及适应性管理提供科学依据，同时推动我国草原生态系统碳氮循环在全球变化生态学研究领域中的理论突破。

Livestock grazing is a main land use type on grassland by human, the effect mechanism of carbon and nitrogen allocation and coupling relationship under different grazing intensity is key to studying the grassland carbon and nitrogen cycle processes. At present, the mechanism of this effect is not clear from the ecosystem perspective and the suitable model is scarce. Our full experiments will be conducted in a representative Leymus Chinensis meadow steppe of Inner Mongolia, where the HulunBuir Grassland Ecosystem Research Station located. The station had built a grazing experiment platform in 2008 and carried out continuous observation during 2009-2018 to quantify the impact of six grazing intensities on grassland biodiversity, above-and below-ground biomass, soil physical and chemical characteristics, soil microbial properties and greenhouse gas emission. Huge data continuously collected from 2009 to 2018. These studies raised new scientific issues which will be focused in this study, we will adopt long-term positioning observation data and model simulations methods to explore carbon and nitrogen allocation in plants above and below ground, carbon and nitrogen dynamics of litter, carbon and nitrogen allocation of soil and microorganisms vertical and interrelationships, and the relationship between carbon and nitrogen in grassland ecosystems and the key factors of plant functional groups, species diversity and soil physical and biological properties were systematically studied, the factors and threshold of maintaining carbon and nitrogen stability were identified under different grazing intensities; At the same time, a carbon and nitrogen cycle process model suitable for the meadow grassland ecosystem was established to evaluate and predict the effects of grazing disturbance on carbon and nitrogen balance and carbon and nitrogen allocation in grassland ecosystems; The comprehensive response mechanism of carbon and nitrogen allocation and its coupling relationship to grazing disturbance in meadow grassland was revealed from ecosystem perspective. This project will not only provide theoretical basis for the rational utilization and adaptive management of the China steppe, but also greatly promote the theoretical breakthrough of carbon and nitrogen cycle of grasslands in the field of global change ecology research in China.