青藏高原高寒草地不仅是我国重要的畜牧业生产基地和生态安全屏障，也是当地牧民赖以生存的居所。然而，在人类活动加剧及全球变化影响下，高寒草地生态环境恶化，进而引发畜牧业发展受阻，牧民返贫等一系列社会、环境问题。为遏制草地退化形势，中央及地方政府出台了一系列草地管理政策，以期通过调整草地管理模式来解决草地退化问题。然而，这些草地管理政策的成效在科学家及政策制定者间还存在争议。因此，当前极重要的挑战是研究可持续的草地管理模式以保护区域生态、支持畜牧业生产以及提高牧民生计。放牧是草地管理的基本手段，其核心是放牧系统单元，放牧系统单元是放牧过程中形成的草地、畜群、人居三位一体的动态稳定格局，具有维持牧业生产、牧民生计和草地健康等多方面功能，是一种畜牧业“社会-生态”耦合系统。

为探究不同草地管理模式对放牧系统单元的影响，本研究基于制度分析与发展框架（IAD, Institutional Analysis and Development framework）和放牧系统单元相关概念，以青藏高原黄河源区海南州、果洛州、黄南州共7个牧业县为例，通过入户访谈与野外样方调查的方法收集数据，共收集有效问卷329份，开展36份样方调查，问卷访谈主要涉及牧户个人及家庭基本信息、草畜情况、草地状况感知、收入状况等，样方调查包括植物群落调查、地上生物量取样、土壤采样用于理化性质分析。采用基于IAD框架而开发的智能体决策模型（PIDM，Participants Intellectual Decision model），二元Logistic回归和“生产-生态-生计”权衡分析模型，利用定性与定量相结合的方法，分析牧户草地管理模式选择的主要影响因素及草地管理模式对放牧系统单元结构与功能的影响。主要研究结论如下：

（1）随着草地承包经营权分置为草地承包权和草地经营权，草地经营权可以在牧民之间进行流转。高寒牧区出现了多种多样的草地管理模式，主要包括合作草地管理模式：联户经营管理和合作社管理，以及单独管理：单户草地管理和公共草地管理。尽管在现行草地管理制度下，牧民可以通过草地流转进行草地资源的重新配置，以选择适宜的草地管理模式，但仍有77%以上的牧民选择单户草地管理模式。

（2）牧民草地管理模式的选择受多种因素的影响。其中个人和家庭变量集中的“受访者性别”（OR=3.214）和“草地面积”（OR=1.031）；制度与规则变量集中的“草地围封”（OR=0.487）；市场和环境变量集中的“村庄规模”（OR=1.112），“到城镇的距离”（OR=1.012）和“合作社的数量”（OR=1.024）；认知与改革变量中的“草地状况变好”（OR=1.992）和“想要去城市居住生活”（OR=0.347）是影响牧民是否选择合作草地管理模式的主要影响因素。

（3）不同草地管理模式对放牧系统单元草地-畜群-人居结构的影响各不相同。单户草地管理下草地条块化分割、牲畜分散化经营以及人居个体化管理会导致放牧系统单元结构失衡；公共草地管理开放进入的草地状况以及人居管理途径的阻断加速了放牧系统单元的崩溃；联户经营管理，通过小规模、粗放式的半定居游牧模式在一定程度上重构了放牧系统单元；合作社管理的划区轮牧模式使放牧系统单元的结构得到进一步优化。

（4）不同草地管理模式对放牧系统单元生态-生产-生计单独功能的影响不同。联户经营管理下放牧系统单元拥有最高的生态功能（0.78），公共草地管理下放牧系统单元拥有最高的生产及生计功能（0.59和0.59）。不同草地管理模式对放牧系统单元生态-生产-生计功能间权衡关系的影响不同。联户经营管理下放牧系统单元多种功能间权衡最大（RMSE=0.39），而合作社管理下放牧系统单元多种功能间权衡最小（RMSE=0.13）。同时，由于权衡关系的存在，放牧系统单元多功能总效益在不同草地管理模式间没有显著性差异。

综合不同草地管理模式对放牧系统单元结构和功能的影响，本研究认为合作社管理若经适当的设计改进，具有实现草地可持续管理的潜力。具体改进措施应包括：加强合作社成员间互相监督以改善草地生态状况；引入高新技术以提高畜牧业产出效率；细化劳动力分配以实现生计多样化。

The Qinghai-Tibetan Plateau of China, known as the “Roof of the World”, composed the largest alpine grassland in the world. In addition to support the development of local husbandry, the alpine grassland plays an important role in protecting the local and global ecology. Moreover, it is a living space for local residents. However, in recent years, the intensification of human activities as well as the impact of global change have greatly affected the vulnerable alpine grassland, caused widespread grassland degradation, leading to a series of social and ecological problems such as land desertification and poverty returning of local pastoralists. To alleviate this dilemma, the central and local governments of China had launched several grassland management policies in order to solve this problem by adjusting grassland management practices. However, the impacts of these reforms to grassland management practices and the pastoral social-ecological system are widely debated by scholars and policy analysts. Hence, developing sustainable grassland management practices is a key challenge related to the protection of regional ecological environments, the provision of livestock production and the improvement of pastoralist welfare in the alpine grassland. Grazing system unit is a stable pattern of grassland, livestock and human residence, which is formed in the process of grazing management. The grazing system unit can provide multiple functions including support human livelihoods and livestock production and protect ecological conditions as is a coupled “social-ecological” system. In order to explore which management practice can achieve the goal of sustainable grassland utilization, seven counties in the source region of the Yellow River on the Qinghai-Tibetan plateau were selected as case sites, and the qualitative and quantitative methods were applied to analyze the influence of different grassland management practices on the structure and function of grazing system unit. The main conclusions are as follows:

1. With the implementation of STPR（Separating Three Property Right）policy, the rural land contract-use right has been separated into contract right and use right. As a consequence, two types of grassland management practices appeared: coo-management practices including shareholding cooperative grassland management (SCGM) and joint household grassland management (JHGM), and non-cooperative management practices including individual grassland management (IGM) and communal grassland management (CGM). It is, however, evident that there is still a large number of herdsmen (more than 77%) adhere to the individual management practices when the grassland management options were more flexible.

2. The respondents’ gender, grassland area, village scale and location, grassland condition perception were significantly positively associated with the pastoralists’ willingness to cooperative grassland management practices, while grassland fence and urban life expectance was negatively associated with it.

3. The influence on the structure of grazing system unit varied under different grassland management practices. the IGM practice, the decentralized management of livestock and the individualized management of human settlements led to the imbalance of unit structure of grazing system with the fragmentation of grassland. The open access of grasslands under CGM practice and the blocking of human settlements management accelerated the collapse of grazing system units. JHGM practice reconstructed the grazing system unit to a certain extent through the small-scale and extensive semi-settled nomadic mode. The zoned rotational grazing mode managed by the SCGM practice further optimized the grazing system unit.

4. Ecological, productivity and livelihood functions and the trade-off of multiple functions of grazing system unit varied with different management practices. JHGM led to the highest ecological benefits, while CGM led to the highest benefits for livestock production and livelihood welfare. SCGM resulted in the lowest level of trade-offs as well as relatively high total benefits among multiple objectives in the ecological, productivity and livelihood dimensions. while the overall benefit of grazing system unit under multiple-functions approaches remains stable due to the existence of trade-offs.

The SCGM showed great potential to achieve sustainable grassland utilization if properly designed. Suggestions for improvement were proposed as follows: strengthening mutual supervision among members of cooperatives to improve the ecological condition of grasslands; introducing new and high technology to improve the output efficiency of animal husbandry and diversify livelihoods by detailing labor distribution.