放（禁）牧梯度下高寒草甸水源涵养功能效应及最适放牧强度(封育年限)的研究

Grazing，is one of the important disturbances in grassland by human activity. Over grazing, as well as global climate warming has resulted in the ecosystem degradation of the alpine meadow in Qinghai-Tibetan Plateau. Fencing and proper grazing management are good measures and has attracted a lot of interest in the restoration of the degraded grassland. But it is still unclear that the quantitative assessment on the influence of grazing and fencing on the ecosystem water conservation capacity. What's the balance between the water conservation capacity and the optimum grazing intensity or fencing years? In this study, basing on the established experiment platform including grazing intensity gradients, different fencing years and vegetation-soil carbon-nitrogen-water cycling, we will study layered soil moisture, precipitation infiltration and ecosystem evapotranspiration. Vegetation community characteristics, soil physical and chemical properties will also be investigated. Through these studies, soil water conservation and holding capacity in the different grazing management of the grassland will be estimated. Influence of the grazing intensity on the water conservation will be quantized. Relationship between the water conservation and retention capacity and evapotranspiration with the parameter of the vegetation and soil will be analyzed. Optimum grazing intensity and fencing years which is good for water conservation in alpine meadow will be discussed. The results can provide some theoretical basis to protect the water conservation of the alpine grassland in Qinghai-Tibetan Plateau.

放牧干扰是人类活动影响草地生态系统重要的方式之一。过度放牧叠加气候温暖化导致了青藏高原高寒草甸的退化。恢复退化草地过程中围栏封育、适度放牧是良好的措施而受到高度重视。但如何定量化评估不同放牧强度及不同封育年限对高寒草甸生态系统水涵养功能影响？土壤最大持水能力与最适宜的放牧强度或封育年限有怎样的平衡关系？需做深入探讨。本研究拟依托海北高寒草甸建立的放牧梯度和不同封育年限及植被-土壤碳-氮-水循环过程研究平台，通过放（禁）牧梯度实验区土壤湿度、水分渗漏、植被蒸散等生态水文要素的监测研究，结合植被群落特征和土壤理化性状的调查，估算放(禁)牧梯度下土壤持水现状和潜力；量化放（禁）牧梯度下水源涵养功能的效应；解析土壤贮水量、持水力、植被蒸散与放（禁）牧梯度下相关植被和土壤参数的关系；探索高寒草甸生态系统土壤最大持水能力与最适放牧强度或最适封育年限的平衡模式，为保护高寒草甸水源涵养功能提供理论依据。

围栏封育和适度放牧是恢复退化草地的重要措施,二者对高寒草甸生态系统水涵养功能影响如何？高寒草甸生态系统水涵养功能的影响因素有哪些？本项目依托海北高寒草甸建立的放牧梯度和不同封育年限及植被-土壤碳-氮-水循环过程研究平台，量化放（禁）牧梯度下高寒草甸的水源涵养功能效应；探索高寒草甸生态系统土壤最大持水能力与最适放牧强度或最适封育年限的平衡模式。项目研究结果表明:（1）不同牧压梯度下高寒草甸植被实际耗水量在生长季的变化特征基本一致，但总体上来讲短期禁牧（2年）与重度放牧的植被实际耗水量较大，植被实际耗水量与降水量呈极显著正相关关系。（2）随着封育时间的延长，土壤饱和持水量、毛管持水量和田间持水量均提高。土壤持水量与地下生物量、土壤有机质含量和土壤孔隙度均呈现显著的正相关关系，而与土壤容重出现极显著的负相关关系.（3）仅针对土壤持水能力而言，并非封育时间越长越好，封育达到5～6年左右时土壤最大饱和水量达最大。表明中度放牧和封育5-6年有利于高寒草甸水源涵养功能的提高。迄今为止，研究成果共发表中英文论文9篇，其中SCI（E）论文3篇。