2001年～2015年伊犁河谷草地植被覆盖度时空变化特征

Spatiotemporal dynamics of grassland fractional coverage in Yili Valley of Xinjiang from 2001 to 2015

基于MODIS NDVI数据,利用像元二分模型反演植被覆盖度,结合DEM数据及差值分析方法对伊犁河谷2001年~2015年草地植被覆盖度的时空变化特征进行了研究.得出如下结论:1)受持续畜牧超载及气候条件恶化影响,2001年~2015年伊犁河谷草地盖度持续降低,15a内全区草地平均盖度降低11.09%,90.04%草地的植被盖度出现不同程度的降低,但主要为降幅<0.10的轻度降低,1 000~2 250m海拔范围平均降幅最大;2)草地盖度变化主要表现在高覆盖草地持续减少,以及盖度降低草地的面积增大和降幅增高,并空间上逐步向高海拔区域延展.3)得益于草地保护政策的实施,2010年~2015年植被盖度降低速度明显减慢,但其降低总趋势未有改变.

Based on data of MODIS NDVI and DEM, the fractional coverage of the grassland in Yili Valley of Xinjiangby was extracted using dimidiate pixel model, and its spatiotemporal variations during the 2001-2015 period were investigated. Results showed.- 1） affected by persistent livestock overload and worsening of climatic condi- tions, grassland coverage in Yili Valley continued to decrease in 2001-2015, and the average coverage in the whole area decreased by 11.09% in 15 years. The percent of grassland with reduced coverage mounted to 90.04% while mainly slight decrease with the amplitude less than 0.10. Fractional coverage of grassland located among 1 000-2 250 m in altitude decreased the most on average. 2） The decrease of grassland coverage mainly manifested in the continuous decrease of the high coverage grassland area, and increase in the area as well as descending amplitude of grassland with reduced coverage which is also expanding towards high altitudes. 3） Benefiting from the implementation of grass-land conservation policies, decrease rate of vegetation coverage of grassland in Yili Valley slowed down significantly during the period of 2010-2015, though the general down- ward trend did not change.