2000-2018年天山中段高海拔草地暖季承载力

草地是新疆重要的植被类型，快速评价区域草地生产力状况，揭示高海拔草地暖季食草动物承载力，对典型区域草地与食草牲畜平衡管理具有重要意义。为克服传统实地取样方法在数据可获取性、多年监测连续性、区域覆盖性等方面的限制，利用MODIS MOD17A3H/NPP数据产品，以新疆和静县为研究区，探索草地地上生物量（Aboveground Biomass，AGB）估算模型在高海拔草地应用的有效性，分析研究区草地AGB的时空变化规律，探讨其多年载畜状况。结果表明：1）基于MODIS MOD17A3H数据模拟的草地地上净初级生产力（Aboveground Net Primary Productivity，ANPP）与已有文献获取的实地数据相比，均方根误差（Root Mean Square Error，RMSE）处于3.23～11.89 g/m2之间，估算结果具有较高精度。2）研究期内（2000-2018年）研究区AGB均值为1 252.34 kg/hm2，且存在波动上升的趋势，其线性增长率为7.78 kg/(hm2·a)（P<0.01），草地AGB整体处于轻微上升趋势，AGB增长的草地占比达74.90%。3）研究期内年均地上干草产量均值为15.01万t，其中海拔>2 500 m的高寒草原及高寒草甸干草产量最大，占比分别为24.20%及57.46%，修正后可利用干草产量为8.62万t。4）研究区草地理论载畜量多年均值为24.26万～31.94万羊单位，不考虑自然及管理因素修正的理论承载力为31.94万羊单位，草地欠载2.99%；修正后理论承载力为24.26万羊单位，草地超载27.82%。研究结果可为制定区域国土管理制度和牧业规划政策提供参考，对促进区域自然资源可持续发展具有积极作用。

Carrying capacity of high-altitude grassland in warm seasons in the middle section of Tianshan Mountain from 2000 to 2018

Abstract: Grassland is an important vegetation type in Xinjiang of western China, particularly on the coordinated development of ecological protection and animal husbandry. It is of great significance to rapidly and accurately evaluate the productivity of regional grasslands, thereby revealing the carrying capacity of herbivores in the warm season of high-altitude grasslands, especially for the balanced management of regional grasslands and herbivorous livestock. However, there are only a few reports on the temporal and spatial changes of grassland Aboveground Biomass (AGB) in high-altitude regions using long-term series. It is necessary to effectively evaluate the carrying capacity considering some limiting factors. Taking the Hejing County of Xinjiang as the research area, this study aims to explore the spatiotemporal dynamics and carrying capacity of the grassland AGB using MODIS 17A3H/NPP (Net Primary Productivity, NPP) data products. An estimation model was also proposed to improve the traditional field sampling, in terms of data availability, multi-year monitoring continuity, and regional coverage. The natural and management factors were considered to further modify the model, according to the grassland type, landform, and township. The results showed that: 1) The Aboveground Net Primary Productivity (ANPP) of grassland presented a Root Mean Square Error (RMSE) value of 3.23-11.89 g/m2, indicating a higher accuracy. 2) The AGB average value was 1 252.34 kg/ hm2 during the study period (2000-2018), indicating a fluctuating upward trend. Specifically, the linear growth rate was 7.78 kg/(hm2·a) (P<0.01), and the overall AGB of grassland was a slight upward trend, where the proportion of grassland with the AGB growth reached 74.90%. The degradation was distributed mostly in the areas with a slope of more than 30%. 3) The annual average aboveground hay was 150 100 t. Among them, the alpine grassland and meadow over 2 500 m produced the largest hay, accounting for 24.20% and 57.46%, respectively. The available hay was reduced to 86 200 t after revision. 4) The average theoretical carrying capacity of grassland in the study area was 242 600 to 319 400 heads. The theoretical carrying capacity of standard sheep without considering natural and management factors was 319 400 heads, the underload of grassland is 2.99%; after revised the carrying capacity was 242 600 heads, and the grass was overloaded by 27.82%, it further illustrated that there was a certain overload risk in the development of grassland animal husbandry in the study area. The research results could provide references for the formulation of regional land management and animal husbandry planning policies, and played a positive role in promoting the sustainable economic development of regional natural resources. The average theoretical carrying capacity of grassland was 242 600 to 319 400 heads. The theoretical carrying capacity of standard sheep was 319 400 heads without considering the natural and management factors, where the underload of grassland was 2.99%. After that, the carrying capacity was 242 600 heads, and the grass was overloaded by 27.82%. Consequently, there was a certain overload risk in the development of grassland and animal husbandry in the study area. The findings can provide a strong reference for the decision-making on the land and animal husbandry, thereby promoting the sustainable development of regional natural resources.