陕西吴起植被动态及其与气候变化的关系

使用归一化植被指数(normalized difference vegetation index,NDVI)资料,分析了陕西省吴起县1982-2003年NDVI的演变情况及其与气候变化的关系。结果表明,22年来植被覆盖状况尽管有波动起伏,但整体在持续转好,表现在低覆盖率植被面积在减少,高覆盖率植被面积在增加;年平均NDVI与降水量呈正相关,植被覆盖的改善有利于减小风速;从季节平均值来看,春季降水量与夏季NDVI、夏季降水量与秋季NDVI的相关性均极显著(P<0.01),并且夏秋两季的降水量与年NDVI相关性也显著,说明降水量是影响吴起县植被分布状况的关键性因子;春夏季蒸发量与夏季的NDVI均呈极显著的负相关(P<0.01);春夏季相对湿度与夏季的NDVI呈极显著的正相关(P<0.01),冬季相对湿度与冬季的NDVI呈极显著的负相关(P<0.01)。

Vegetation change and its relations with climate variables in Wuqi of Shaanxi

By using the monthly GIMMS normalized difference vegetation index(NDVI)data and local meteorological records,the inter-annual vegetation change and its relations with the climate variables in Wuqi County of Shaanxi Province in 1982-2003 were examined.The results showed that in the past 22 years,the vegetation coverage in the County had an overall improvement though undulation was observed.The areas with lower vegetation coverage decreased,while those with higher vegetation coverage increased.The annual NDVI had a positive correlation with precipitation,and the improved vegetation coverage benefited the decrease of wind speed.There was a significant positive correlation between the precipitation in spring and the NDVI in summer,and the precipitation in summer and the NDVI in autumn.In the meanwhile,the correlation of annual mean NDVI with the precipitation both in summer and in autumn was also significantly positive,indicating that precipitation was the key factor determining the distribution of vegetation in Wuqi.The NDVI in summer had a significant negative correlation with the evaporation in spring and summer but a positive correlation with the relative humidity in these seasons,while the NDVI in winter had a significant negative correlation with the relative humidity in this season.