陕北地区NDVI对水热条件年内变化的响应及其空间特征

利用陕北地区1999—2010年GIMMS-NDVI数据，结合同期气温和降水资料，基于GIS软件和时滞互相关方法，以陕北地区植被覆盖对气温、降水的响应关系为主线，通过生态功能区划和植被类型两个层面分析了水热条件的季相变化同各旬NDVI均值（TN，Ten-day NDVI）变化之间的关系，结果如下:（1） 陕北地区生态亚区的TN与旬平均降水TP（Ten-day Precipitation）的相关程度从大到小依次是:高植被覆盖率（人工植被）、低植被覆盖率、高植被覆盖率（自然植被）、高植被覆盖率（人工—自然混合植被）；各个生态亚区的TN与旬均温TT（Ten-day Temperature）的相关程度从大到小依次是:高植被覆盖率（人工—自然混合植被）、低植被覆盖率、高植被覆盖率（自然植被）、高植被覆盖率（人工植被）。（2） 陕北地区各个生态亚区植被NDVI对水热条件的滞后时间一致，长短排序依次是:高植被覆盖率（人工植被）、低植被覆盖率、高植被覆盖率（自然植被）、高植被覆盖度（人工—自然混合植被）。（3） 陕北地区不同植被类型对水、热条件的响应程度由高到低依次是耕地、草原、密集灌丛、沙漠和林地，所有植被类型对降水的响应均比温度快。水热条件对陕北不同植被类型的影响程度从大到小依次为耕地、草原、密集灌丛、沙漠和林地。同一植被类型的不同亚类受水、热条件影响程度和响应速度均有差异。

Intra-Annual Response of NDVI to Changes in Temperature and Precipitation and Its Spatial Characteristics in Northern Shaanxi

By combing GIMMS-NDVI data and the temperature and precipitation data from 1999 to 2010 in northern Shaanxi, and based on delay cross-correlation method, temporal and spatial characteristics of the relationship between hydro-thermal condition and vegetation cover were analyzed. Results show that: (1) different ecological subregions in northern Shaanxi differently respond to temperature and precipitation condition, the descending order of the correlation between TN(Ten-day NDVI) and TP(Ten-day Precipitation) is high rate of vegetation coverage(hybrid vegetation), low rate of vegetation coverage, high rate of vegetation coverage (natural vegetation), high rate of vegetation coverage(artificial vegetation).The descending order of the correlation between TN and TT(Ten-day Temperature) is high rate of vegetation coverage(hybrid vegetation), low rate of vegetation coverage, high rate of vegetation coverage(nature vegetation), high rate of vegetation coverage(artificial vegetation); (2) one ecologic zone has the same lagged effect on water and heat, the descending order of the lay time is high rate of vegetation coverage(artificial vegetation), low rate of vegetation coverage, high rate of vegetation coverage(natural vegetation), high rate of vegetation coverage(hybrid vegetation); (3) different vegetation types respond to water and thermal condition differently. The descending order of the responding degree for each vegetation type is arable land, grassland, dense shrub, desert, woodland. All plants respond to precipitation faster than temperature. Descending order of requirement of water and heat for different vegetation types is arable land, grassland, dense shrub, desert, woodland. The influence of water and heat on the same plant in different sub-categories is different.