2000-2013年三江源植被NDVI变化趋势及影响因素分析

基于2000-2013年三江源MODIS NDVI数据,本文系统地分析了三江源植被生长季累计NDVI的时空变化特征,并结合三江源生态保护与建设工程实施的相关统计数据,探讨了人类活动对三江源植被变化的影响,最后通过气候因子与生长季累计NDVI的相关性分析,揭示了影响三江源不同地区植被变化的主要气候限制因素。结果表明,2000-2013年三江源植被NDVI整体上呈增加趋势,NDVI明显增加的区域面积比例达17.84%,主要分布于研究区的西部和北部;明显减少的区域仅占0.78%,多零星分布于研究区中部;NDVI变化稳定或没有显著变化趋势的区域面积比例为59.64%,主要位于研究区东部和南部。三江源生态保护与建设工程的实施虽然促进了植被恢复,但对区域植被整体变化的影响有限,研究时段内区域植被整体好转主要受气候因素控制。西部长江源区的植被生长主要受气温影响,东北部黄河源区主要受降水制约,南部澜沧江源区降水和气温的限制性均不明显。

Analysis of NDVI Change Trend and Its Impact Factors in the Three-River HeadwaterRegion from 2000 to 2013

Based on the MODIS NDVI data for the Three-River Headwater Region from 2000 to 2013, this study first systematically analyzed the spatial-temporal change pattern of yearly accumulative NDVI during the growing season. Then, the impacts of human activities on the change of NDVI were explored based on the statistical data collected in the ecological protection and construction projects implemented within the study area. Finally, correlations between the NDVI data and climate factors were acquired, and the key limiting climate factors that could impact the vegetation change within different parts of the study area were discussed. Results show that, the accumulative NDVI during the growing season increased overall from 2000 to 2013. Specifically, areas with apparent increase of NDVI accounted for 17.84% of the study area and were mainly distributed in the western and northern parts, while areas with apparent decrease of NDVI covered only 0.78% of the Three-River Headwater Region and were sporadically located in the central part. NDVI in the eastern and southern parts primarily presented a stable change trend or had no significant change trend, and its area ratio was 59.64%. Although the ecological protection and construction projects implemented within the Three-River Headwater Region had promoted the vegetation restoration, NDVI change was mainly affected by the climate factors within the whole study area, since the impacts of human activities on the regional vegetation change were limited. Spatially, NDVI in the western part of the study area (Yangtze River source region) was strongly affected by temperature, while in the northeastern part (Yellow River source region) it was affected more by precipitation. In the southern part (Lancang River source region), however, vegetation growth was affected neither by precipitation nor by temperature.