秦巴山区植被覆盖与土壤湿度时空变化特征及其相互关系

基于2001-2014年MODIS-NDVI和MODIS-LST数据,利用温度植被干旱指数对土壤湿度进行遥感反演,分析了秦巴山区植被覆盖与土壤湿度时空变化特征及其相互关系。研究发现：① 秦巴山区植被覆盖与土壤湿度均呈增加趋势;② 植被覆盖整体水平较高且表现出“四周低,中间高”的空间分布特征,土壤湿度整体表现出“北低南高”的空间分布特征,大体上二者呈现出空间分布正相关性;③ 植被改善趋势表现明显,显著改善区分布分散,无明显集中区域,退化区域主要集中于北部渭河沿岸及东部边缘少量地区;土壤湿度增长态势明显,增大区分布于除西北边缘及东北边缘外的几乎整个研究区中,减小区域面积小且大部分表现不显著;④ 秦巴山区植被覆盖与土壤湿度时空变化上呈现出明显的正相关性,其中69.71%的区域表现出土壤湿度增大-植被覆盖改善的特征,分布于研究区除四周边缘地带外的大部分地区。

Spatio-temporal Variation and Interrelationship of Vegetation Cover and Soil Moisture in Qinling-Daba Mountains

Qinling-Daba Mountains, as the geographical dividing line in central China, is the main water source area of the middle line project of transferring water from south to north, and also a sensitive area of the regional response to the global climate change. The spatio-temporal variation of vegetation, as a main component of terrestrial ecology system, represents the comprehensive response to climate change and human activities. Based on the MODIS data during 2001-2014, this study estimated the soil moisture using temperature vegetation dryness index, dynamically monitored the distribution characters and spatiotemporal variations of vegetation cover and soil moisture, analyzed its change trend, forecasted its future trend, and explored the interrelationship between vegetation cover and soil moisture in Qinling-Daba Mountains. The main conclusions are as follows: (1) Vegetation showed an increasing trend in Qinling-Daba Mountains during 2001-2014 years, as well as soil moisture, which respectively represented the best in 2010 and 2011, then both showed declining trends. (2) Vegetation distribution had a feature of “higher overall and lower in the middle”, while soil moisture with “lower in the north and higher in the south”, which showed a positive spatial correlation. (3) Vegetation had an obvious improving trend, and the significantly improved areas are dispersionally distributed, with no obvious concentration areas, and degraded areas were mainly concentrated in the north of Weihe River and a few areas along the eastern edge. Soil moisture increased significantly, and the increased areas distributed almost over the entire area except the northwest and northeast edge, and the reduced areas were small and not noticeable. The reverse variation of vegetation cover was stronger than continuous change, but soil moisture was just the opposite. In predicted future, in 44.36% of the study area, dispersed in entire area, the vegetation cover will undergo a process from increase to reduction, while soil moisture will continue to grow in 43.98% of the study area, including Qinling mountain in Shaanxi Province, Daba mountain in Sichuan province, and some parts of Jialing River basin and Han River. (4) The correlation between vegetation cover and soil moisture is positive. Nearly 69.71% of the study area showed an increasing tendency in both vegetation cover and soil moisture content, which was distributed in almost all parts of the study area except for the edges.