1999—2010年中国西北地区植被覆盖对气候变化和人类活动的响应

Response of Vegetation Cover to Climate Change and Human Activities in Northwest China During 1999-2010

中国西北地区气候干旱,频繁出现沙尘天气,属于生态脆弱区域,而植被变化是生态系统对气候变化响应的指示器,研究其变化对改善西北生态环境具有重要意义。本文利用1999—2010年归一化植被指数(NDVI)以及气象数据研究中国西北地区植被覆盖时空变化,以Sen趋势度结合Mann-Kendall检验、相关和偏相关分析以及残差法分析人类活动和气候变化对植被覆盖变化的影响。结果表明:西北地区植被覆盖整体呈增加趋势,但在局部地区气候干旱少雨和人类活动抑制植被生长。植被变化强度空间差异是人类活动和气候要素共同作用的结果:气温高,降水少,大部分地区植被覆盖与气候要素相关显著,并且植被变化对气温和降水的响应存在一定滞后时间;蒸发量大于降水量,人类引水灌溉弥补降水不足,使得农业植被呈增长趋势。新疆北部地区植被覆盖呈下降趋势,原因是气候干旱、沙漠化严重会抑制植被生长,人类活动频繁、城市扩建同样会破坏植被生长。

As a typical ecological fragile area,Northwest China is marked by drought and dust climate.Vegetation is known as an indicator of the terrestrial ecosystems response to climate change.In th paper,the normalized difference vegetation index(NDVI)from1999to 2010 and meteorological data are employed to investigate the spatiotemporal variation of vegetation cover over Northwest China,and the effects of human activities and climate change on vegetation cover change were also analyzed by using Sen-trend combined with the Mann-Kendall test,correlation and partial correlation analysis and residual method.The results showed that the vegetation coverage presented an increasing trend over Northwest China,but the vegetation growth was still hindered in some areas.The spatial difference of vegetation cover change may be the results of the interaction between human activities and climate change.Vegetation cover was significantly correlated with climatic factors in most area.What's more,the response of vegetation cover change to temperature and precipitation had a lag time.Evapotranspiration was greater than precipitation,and human irrigation had to make up for the lack of water,which made agricultural vegetation area increase.The vegetation cover decreased in Northern Xinjiang due to drought and desertification,human activities and urban expansion also inhibited the growth of vegetation seriously.