内蒙古草地生产力及载畜量变化分析

Changes in Grassland Productivity and Livestock Carrying Capacity in Inner Mongolia

草地生产力和载畜量历来是草地生态系统研究的热点问题,但多年来的研究成果却未能有效地揭示草畜供求关系。以内蒙古3个植被类型(草甸草原、典型草原、荒漠草原)为研究对象,基于MODIS遥感数据,应用光能利用率模型(CASA模型)和连续3年(2011—2013年)大量成对(围栏和放牧)的野外样地调查数据,分析了不同类型草地净初级生产力(NPP)、牧草利用率及超载情况。结果表明:(1)2011—2013年内蒙古草甸草原、典型草原、荒漠草原NPP平均值分别为122、116.2和39.3 g?m^(-2)?a^(-1);(2)2011—2013年内蒙古草甸草原、典型草原、荒漠草原利用率分别为41.28%、40.38%、38.05%;(3)2011年3种类型草地均过度放牧,超载率分别为43.59%、44.95%和75.92%,2012年草甸草原和荒漠草原过度放牧,超载率为1.21%、57.53%,2013年荒漠草原过度放牧,超载率为57.38%,而2012年典型草原,2013年草甸草原和典型草原与理论载畜量相比尚有127.4、1 158.82、392.33万羊单位潜力,可持续放牧。因此,在内蒙古草原牧场放牧管理时,应结合不同类型草地和降水条件,在荒漠草原及干旱年份适当减少载畜量从而实现草畜动态平衡。研究结果可为草地放牧管理决策提供参考依据。

Because of the combined effects of human activities and climate change, the grasslands in Inner Mongolia show varied degrees of overgrazing. Although grassland productivity and livestock carrying capacity have always been subjects of interest in grassland ecosystem research, the findings from many years of research, however, have failed to effectively translate into improved supply-demand relationships of livestock forage. In addition, the degradation of the grassland ecosystems remains a concern. Therefore, in-depth analyses of grassland productivity, livestock carrying capacity, and the supply-demand relationship of livestock forage will have significant impacts on the sustainable development of grasslands and the forage-livestock balance in Inner Mongolia. Based on MODIS remote sensing data, three types of vegetation （meadow steppe, typical steppe, and desert steppe） in Inner Mongolia were studied using the light energy utilization model （CASA model）. The net primary productivity （NPP）, pasture utilization, and over capacity conditions were analyzed using paired field samples （fenced and grazed） over three consecutive years （2011-2013）. The results showed the following： （1） From 2011 to 2013, the average NPPs of meadow steppe, typical steppe, and desert steppe in Inner Mongolia were 122.0, 116.2 and 39.3 g·m^-2·a^-1, respectively. （2） From 2011 to 2013, the grassland utilization rates for meadow steppe, typical steppe, and desert steppe were 41.28%, 40.38% and 38.05%, respectively. （3） In 2011, all three types of grasslands were overgrazed. The rates of overgrazed areas were 43.59%, 44.95% and 75.92% for meadow steppe, typical steppe, and desert steppe, respectively. In 2012, the meadow steppe and desert steppe were overgrazed, with utilization rates of 1.21% and 57.53%, respectively. In 2013, the desert steppe was overgrazed with a utilization rate of 57.38%. The typical steppe in 2012, the meadow steppe in 2013, and the typical steppe in 2013 still had 1.274, 11.588 2, and 3.923 3 million sheep units, respectively, of potential grazing capacity compared with the theoretical livestock carrying capacity. These results indicate that these grasslands could support sustainable grazing. Hence, in Inner Mongolia, grassland pasture management measures should consider different types of grasslands and precipitation levels in order to reduce livestock carrying capacity for desert steppes and drought years, thereby achieving dynamic forage livestock balance. The findings of this study will provide reference data for grassland pasture management.