玛多县大型野生食草动物种群数量对草畜平衡的影响研究

以黄河源区玛多县为研究区域,利用无人机遥感技术调查了县域内藏野驴、藏原羚、岩羊等大型野生食草动物和家畜的种群数量,利用降尺度算法生成了2016年玛多县30 m空间分辨率的产草量数据,在此基础上估算了包括野生动物和家畜在内的草畜平衡状况,分析了大型野生食草动物对玛多县草畜平衡的影响。结果表明:1)通过飞行样带内种群密度,推算了玛多县内大型食草动物种群数量,分别与统计数据、暖季调查结果对比验证,估算出2017年冷季藏野驴、藏原羚和岩羊分别为1.71、1.60和0.93万匹(只),家牦牛、藏羊和马分别为7.08、10.22、0.12万头(匹、只),大型野生食草动物和家畜总计47.5万羊单位,大型野生食草动物羊单位数量与家畜羊单位数量之比为1∶4.5;2)仅考虑饲养家畜,载畜压力指数为1.13,表明草地略微超载;在综合考虑饲养家畜和野生动物的情况下,载畜压力指数为1.38,表明草地中度超载;3)若没有将大型野生食草动物纳入草畜平衡核算体系内,载畜压力将被低估22%。超载过牧是造成玛多县草地退化一个主要驱动因素,需人工补饲7.90万t干草或减畜30%才能维持草畜平衡。

Effects of wild large herbivore populations on the grassland-livestock balance in Maduo County

The number of wild large herbivores, including Equus kiang, Procapra picticaudata and Pseudois nayaur was investigated using remote sensing technology or an unmanned aerial vehicle (UAV). The balance of grassland-livestock, including wild and domestic herbivores, was estimated from data (30 m resolution) in Maduo County in 2016 and the effects of wild herbivore population on the balance of grassland-livestock analyzed. The population of large herbivores was estimated from animal density from sample flights, and the results compared with data from summer monitoring. The estimated number of E. kiang, P. picticaudata and P. nayaur were 1.71, 1.60 and 0.93 million respectively, while the number of yak, Tibetan sheep and horses were 7.08, 10.22 and 0.12 million respectively. The number of large wild herbivores present was equivalent to 47.5 million sheep stock units. The ratio of sheep stock units from wild herbivores to the number of domestic herbivores was 1∶4.5. The carrying capacity index of domestic livestock was 1.13, indicating that the grassland was slightly overstocked; the carrying capacity index for wild herbivores was 0.25 and the combined carrying capacity index (1.38) indicated that the grassland was overstocked. Not including wild herbivores in the grassland-livestock balance accounting system resulted in the carrying capacity index being underestimated by 22%. Overstocking is one of the main drivers of grassland degradation in Maduo County; feeding of 79000 tons of hay or reducing livestock numbers by 30% would be required to achieve balance.