渭河流域相对湿度与植被覆盖变化及其响应关系

Changes of Relative Humidity and Vegetation Coverage and Their Reciprocal Response in Weihe River Basin

借助GIS、遥感技术和数理统计等方法,对渭河流域相对湿度和植被覆盖变化进行了研究,定量分析植被恢复对该地区空气相对湿度的影响。结果表明:(1)近60a相对湿度分布具有一定的纬度地带性,存在由北向南递增的特点。相对湿度总体上呈下降趋势,退耕10a间呈微弱上升趋势。(2)退耕10a间植被覆盖呈整体改善,局部恶化的趋势,近1/3的地区植被覆盖基本不变。植被覆盖状况改善较为明显的几个县(市)主要集中在渭河干流及泾河上游、马莲河上游、北洛河中游一带,植被退化的县(市)大多位于渭河中下游、泾河中上游地区。(3)退耕前的50a对于相对湿度影响较大的因子依次为降水、日照和气温。退耕后的10a相对湿度随着植被覆盖状况的改善(退化)而相应上升(下降)。(4)吴旗县冬季和年的相对湿度与NDVI呈负相关,春季和夏季的相对湿度与NDVI呈极显著的正相关。1982—2006年夏季湿润则植被状况较好,夏季干燥则植被状况较差。

Changes of relative humidity and vegetation coverage in Weihe River basin were studied and the effects of vegetation restoration on air relative humidity were analyzed quantitatively by using GIS,remote sensing technology and statistical methods.It was observed that：（1） The relative humidity had a latitude zonal distribution character,increased from north to south.The overall average relative humidity of Weihe River basin declined gradually and presented an upward trend during the last 10 years.（2） The overall vegetation coverage was improved,while the local vegetation coverage presented a bad trend.Nearly a third of basin was stable.Counties（cities） with an obviously improving trend were mainly located along the main stream as well as in the upper reaches of Jinghe River and Malian River and the middle reaches of Beiluo River.Counties（cities） with a degrading trend were mainly located in the middle and lower reaches of Weihe River and the middle and the upper reaches of Jinghe River.（3） Before the implementation of vegetation restoration,the main influence factors were precipitation,sunshine and temperature.After the implementation of vegetation restoration,the relative humidity increased or decreased with the vegetation cover condition improving or degrading.（4） The NDVI in Wuqi County was negatively correlated with the winter relative humidity and yearly averaged relative humidity.There was a significant positive correlation between the NDVI and the relative humidity in spring and summer.During the period from 1982 to 2006,vegetation condition in summer had the same trend as relative humidity.Vegetation condition was better or worse when relative humidity was high or low.