中国华东及其周边地区NDVI对气温和降水的季节响应

地表植被与大气的相互作用过程是地球科学领域的研究重点和热点。本文基于SPOTVGT-NDVI数据和气象站点的气温和降水资料,采用时滞相关分析法,研究了1998年-2011年我国华东及其周边地区四季NDVI对气温和降水的时空响应特征。结果表明,在整个研究区,气温对NDVI的影响大于降水,NDVI与气温在夏季和秋季相关性较高,与降水在秋季和春季相关性较高,冬季NDVI与气温和降水相关性都最低。NDVI对气温响应的滞后期在春季和秋季较短,对降水响应的滞后期在冬季较短,夏季NDVI对气温和降水响应的滞后期都较长。在冬季、春季和秋季,NDVI对气温和降水最大相关系数的空间分布在研究区的南北部差异不明显,在夏季则具有较明显的南北差异。NDVI对气温变化响应的滞后期在春季、夏季和秋季具有较明显的南北差异,对降水变化响应的滞后期除在夏季具有一定的南北差异外,在其他季节空间分布规律性不显著。

Characteristics of Seasonal Response of NDVI to Variations in Temperature and Precipitation in East China and Its Surrounding Areas

The interaction between vegetation and the atmosphere is important in geosciences and has become a research focus in recent years. As a sensitive indicator of surface vegetation coverage and vegetation growth status, the Normalized Difference Vegetation Index (NDVI) has been widely used in environmental, ecological, and agricultural studies. With the time lag correlation method, characteristics of spatial and temporal response of NDVI to variations in air temperature and precipitation in East China and its surrounding areas were comprehensively examined based on SPOT VGT-NDVI data, monthly air temperature, and precipitation data at 135 meteorological stations during the period 1998-2011. Results indicate that across the entire study region, both air temperature and precipitation have an influence on NDVI, but air temperature plays a more prominent role. In general, the correlation between NDVI and air temperature is stronger in summer and autumn, and the correlation between NDVI and precipitation is stronger in autumn and spring. In winter, the correlation between NDVI and air temperature and precipitation seem to be low. The lag time of the maximum NDVI in response to air temperature is shorter in spring and autumn. The lag time of the maximum NDVI in response to precipitation is shorter in winter. In summer, the lag time of the maximum NDVI in response to air temperature and precipitation is longer. Spatial distribution of the maximum NDVI-temperature and NDVI-precipitation correlation coefficients varies slightly between the northern and southern parts of the study region in winter, spring and autumn, but in summer, it shows a marked difference between the northern and southern parts. The lag time of the maximum NDVI in response to temperature exhibits an obvious difference between the northern and southern parts of the study region in spring, summer, and autumn, but the lag time of the maximum NDVI in response to precipitation has a little difference between the northern and southern parts in all seasons except summer. Characteristics of response of NDVI to variations in air temperature and precipitation are closely related to the monsoon climate and the features of farming systems in East China and its surrounding areas. In the northern and middle parts of the study region, temperature rises in spring and drops in autumn quickly, and the precipitation is mainly concentrated in summer. In addition, cropland occupies a larger percentage in East China and its surrounding areas, with relatively consistent sowing- and harvest-time. Both may result in seasonal variations in NDVI and differences in the lag time of the maximum NDVI in response to temperature and precipitation.