Grassland,is one of the most widespread vegetation types in the world,and accounts for nearly 20 ％ of the global land surface.China has abundant grassland resources,and the second largest grassland area of any country.However,in recent years,China's grassland ecosystem has suffered dramatic impairment through human activities and climate change.Grassland in the Heihe River Basin provides necessary resources for the livelihood of local communities.It is therefore important to monitor grassland change.In this study,we assessed historical grassland cover in Heihe River Basin using GIS technology and evaluated land use and land cover change (LUCC) since 1986.We also predicted the future grassland distribution pattern using a CA-Markov Model and land-use transfer matrix,reflecting change in spatial distribution and metabolic indices of grassland.In 1986,the total area of grassland in the Heihe River Basin was 32998 km2,of which 4290 km2 were classed as having high coverage,6372 km2 were classed as having medium coverage and 22336 km2 were classed as having low coverage.In 2000,the grassland area was 23939 km2,and areas with high,medium and low coverage were,respectively,5509,5540 and 12891 km2.In 2011,the grassland area was 24273 km2,and areas with high medium and low coverage were,respectively,5561,5715 and 12996 km2.During the period 1986-2000,the area of grassland in the Heihe River Basin was considerably reduced and severe degeneration occurred.During this period,there was substantial transformation of grassland from high to medium coverage,from medium to low coverage,and from low coverage to unutilized land.During the period 2000-2011,the grassland area in Heihe River Basin increased slightly and transition between the three coverage classes was small.Finally,in 2022 the predicted grassland area of the Heihe River Basin is 24450 km2 with,respectively,5560,5658 and 13232 km2 with high,medium,and low coverage,respectively.%草地是人类生存的基本资源和条件,在全球变化、全球循环和生态系统功能等方面起着非常关键的作用.本文基于GIS技术和1986、2000和2011年黑河流域草地分布数据,采用转移矩阵、草地动态变化度、空间动态度和CA-Markov模型等方法,分析了黑河流域近30年的草地变化,并对其未来分布格局做出预测.结果表明,(1)黑河流域1986年草地面积为32997.71 km2,高覆被草地、中覆被草地和低覆被草地面积分别为4290.02、6371.80和22335.89 km2;2000年草地面积为23939.46 km2,高覆被草地、中覆被草地和低覆被草地面积分别为5508.78、5540.01和12890.67 km2;2011年草地面积为24272.50 km2,高覆被草地、中覆被草地和低覆被草地面积分别为5561.31、5715.01和12996.18 km2,近30年间黑河流域草地面积呈现先减后增的趋势.(2) 1986-2000年期间,黑河流域草地面积大幅减少,且退化严重,高覆被草地主要向中低覆被草地转换,中覆被草地主要向低覆被草地转换,低覆被草地主要向未利用地转换.(3) 2000-2011年期间,黑河流域草地面积小幅增加,各类型草地转化面积较少,保持小幅缓慢上升趋势.(4)在现行趋势下,预测2022年黑河流域草地面积为24449.58 km2,高覆被草地、中覆被草地和低覆被草地面积分别为5560.28、5657.65和13231.65 km2,与2011年相比呈增加趋势,但下游地区草地面积和覆盖度依然较低.
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