放牧强度对典型草原土-草-畜耦合界面水力侵蚀的影响机制

Characters)：Soil and water loss is one of the most prominent environmental problem in the world, but Soil Erosion which led by grazing hasn't been paid enough attention. In view of that, based on the basic theory of Animal Science and Soil Erosion,taking focus on the interaction between plants, livestock and soil and the interaction between plants-livestock-soil with environmental factors, this research will study the coupled discipline in different soil-grass-livestock interface.The study will start from the vegetation types of successional stages in typical steppe; taking grazing pressure and soil hydraulic erosion as index, establsh the empirical models of water erosion in degraded sequence of typical steppe. In this research, field observation and quantify precise observation in the laboratory would be combined to propose a reasonable soil-grass-livestock coupled model and explore the control measures of soil erosion in grazing grassland based on the appropriate stocking rates for different types of grassland which was objectly defined according to water and soil conservation and pasture productivity. This research would provide a scientific basis to restoration and management of erosied and degraded ecosystem in typical steppe to maintain the productivity of grazing grassland ecosystem.

水土流失是全球面临最突出的环境问题，但放牧导致的土壤侵蚀研究并未受到足够的重视。有鉴于此，本研究依据畜牧学和土壤侵蚀学的基本理论，针对不同放牧强度下典型草原区植物-家畜-土壤之间互作机制及其与环境因子之间的联动过程，围绕草丛与地境界面以及草地与家畜界面，从典型草原不同演替阶段的植被类型入手，以放牧压力和土壤水力侵蚀为指标，采用野外实地观测结合基地内定量精准观测，定量研究不同土-草-畜耦合界面水力侵蚀的规律，建立典型草原区植被退化序列上水力侵蚀的经验模型，并基于保持水土和牧草生产力客观界定不同类型草地的适宜载畜量，提出生态经济型的土-草-畜耦合新模式，探索放牧草地土壤侵蚀的控制措施，为典型草原区侵蚀退化生态系统的修复和管理提供科学依据，以维护放牧草地生态系统的生产力。

本项目针对典型草原“有畜”生态系统有别于其他生态系统土壤侵蚀的这一特殊现象，定量研究不同放牧强度下典型草原区土-草-畜耦合界面的草地植被、土壤过程和水力侵蚀的产流、产沙特征，揭示典型草原区不同牧压强度下的土壤水力侵蚀发生发展过程、规律特征。研究结果表明：①随着放牧强度的增加，草地植物群落结构、生产力和多样性的表现并不同步。随着放牧强度的增加，重要值在所有物种中呈先分散再集中的趋势，优良牧草的重要值及比例明显降低，同时群落高度、盖度、生物量显著降低，而群落密度呈相反的趋势，群落地下生物量由深到浅呈“T”形分布；②不同放牧强度对0–10 cm土壤紧实度土壤容重、土壤孔隙度及土壤平均含水量影响显著，对土壤全钾含量影响不显著，对速效钾含量影响显著。随着放牧强度的增加，各土层土壤有机碳、全氮含量均呈先增加后减少趋势，轻度和中度放牧有助于土壤碳氮的积累；③随放牧强度的增加，土壤侵蚀加剧，且伴随的雨强越大，重度放牧导致土壤侵蚀越明显，当坡度为15°、降雨强度为60mm/h、放牧强度为重度放牧的产沙量与产流量分别是坡度为5°、降雨强度为20mm/h、放牧强度为对照（未放牧）时的361.7倍和57.0倍。相同放牧强度下坡度由5°增加到10°的产沙量增加值明显高于由10°增加到15°的产沙量，且随雨强的增大，坡度增加导致产沙量增加的比值减小。其他立地类型一定条件下，随降雨强度的增加产流、产沙量明显增加，同时不同放牧强度、坡度、降雨条件下的总径流量和总产沙量具有较好的二次函数拟合效果。④轻度放牧草地生态系统健康略优于对照，进行适度放牧可以提高草地植物群落的多样性、优良牧草比例、土壤养分等，使草地生态系统依然处于健康稳定的状态。研究结果将可为侵蚀退化草场修复，科学保护与合理利用草地资源，维护草地生态系统的生态生产力提供部分理论和指导依据。