2000~2014年黄土高原植被覆盖时空变化特征及其归因

基于MODIS-NDVI数据,辅以一元线性回归分析、Mann-Kendall检验、Hurst指数等方法,分析了2000~2014年黄土高原植被覆盖时空演变特征及其驱动因素.研究表明:近15年黄土高原NDVI呈显著增加趋势,增速为6.93%/10a(P<0.01);空间上,植被归一化指数,或归一化值被指数Normalized Difference Vegetation Index(NDVI)呈由东南向西北递减的分布格局,高值区主要分布在东南部的土石山区、河谷平原区;同时,500m以下和3500米左右的NDVI值最高;在趋势上,NDVI呈现增加和减小趋势的面积比重分别为88.24%和11.76%;Hurst指数表明研究区未来NDVI变化趋势呈持续性和反持续的比重分别为50.07%和49.93%,其中持续改善和由改善变为退化的面积分别占43.98%和44.28%;降水是影响NDVI变化的主要驱动因子,表现为NDVI随降水的增加而增加;人类活动也是影响NDVI的重要因素,且对NDVI有双重影响.

Spatiotemporal analyses and associated driving forces of vegetation coverage change in the Loess Plateau

Based on the MODIS-NDVI data, this study investigated the patterns of spatiotemporal variation of vegetation coverage in the Loess Plateau during 2000~2014, using the methods of linear regression, Mann-Kendall, correlation analysis and Hurst. In addition, potential factors affecting NDVI variations were identified. The results are as follows: 1) the Normalized Difference Vegetation Index (NDVI) of this study region was significantly increased significant, with a linear tendency being 0.0693/10a during 2000~2014, and vegetation restoration was characterized by three fast-growing periods. 2) As for spatial distribution, NDVI showed a decreasing trend from southeast to the northwest. High values of NDVI were mainly found in Southeast soil stone mountain area and valley plains area. 3) The area with improved NDVI was larger than the degraded area, and accounting for 88.24% and 11.76% of the total study area, respectively. 4) Result of Hurst analyses indicated 50.07% of the study area will keep the current NDVI change tendency in the future. The area with a continuous NDVI increase was predicted to account for 43.98% of the study area. The area, in which NDVI was changed from increase during 2000~2014 to decrease in the future, was predicted to account for 44.28% of the study area. 5) The spatial variation of NDVI was affected by Digital Elevation Model (DEM) and slope. The NDVI was best in the region with the altitude around 3500m and the region with the altitude below 500m. The NDVI was increased with the increase of the slope. 6) The NDVI was mainly affected by the precipitation, and the NDVI was increased with the increase of the precipitation. 7) Human activities can induce both negative effect (through urbanization) and positive effect (through the implementation of Grain to Green).