黑河中游植被覆盖率变化趋势及其驱动因子分析

利用2002~2011年的黑河干流中游归一化值被指数数据获得植被覆盖率变化趋势,选取合适的NDVI阈值将整个区域划分为"绿洲区"和"荒漠区",并分别探讨了地下水埋深、中游耗水量及累积降水量对两种区域面积和植被覆盖率变化的影响。结果表明:黑河干流中游植被覆盖率整体呈增长趋势,由2002年的32%增长到了2011年的36%,对植被覆盖率增长贡献最大的因素为绿洲区扩张,10年间绿洲区面积占比增长了10%;影响绿洲扩张的主要因素为地下水位埋深和中游耗水量,绿洲区植被覆盖率变化较小,可忽略其影响。荒漠区植被覆盖率的变化主要受累积降水量影响。利用地下水位埋深、中游耗水量、累积降水量可预测区域植被覆盖率的变化趋势,区分人类活动和气候变化对区域植被覆盖率的影响是可行的。

Analysis on the changing trend of vegetation cover rate and its driving factors in middle reaches of Heihe River

The changing trend of vegetation cover rate has been obtained by using the NDVI data during 2002 to 2011 in middle reaches of Heihe River. The whole region can be divided into oasis region and desert area by selected suitable NDVI threshold value. The influences of ground water table, water consumption in middle reaches and cumulative precipitation to the areas of two regions and the change of vegetation cover rate were discussed respectively. The results showed that:As a whole the vegetation cover rate in middle reaches of Heihe River was assumedan in creasing trend,from 32% in 2002 had increased to 36% in 2011. The expansion of oasis area was the largest contribution factor for increasing vegetation cover rate. During 10 years, the oasis areas has increased 10%. The main factors to influence the expansion of oasis area were the ground water table and water consumption in middle reaches. But the change of the vegetation cover ratein oasis was rather small,so its influence can be ignored.The change of vegetation cover ratein desert region was major influenced by the cumulative precipitation.So it is feasible by using ground water table, water consumption in middle reaches and cumulative precipitation to forecast changing trend of regional vegetation cover rate and distinguishing the impacts between human activities and climate change on regional vegetation cover rate.