2000~2020年岷江上游植被NDVI时空变化及其地形响应

Spatio-temporal Changes of Vegetation NDVI and Its Topographic Response in the Upper Reaches of the Minjiang River from 2000 to 2020

岷江上游地区承载着不可替代的资源支撑、生态服务与环境调节功能,是国家生态红线的水土流失敏感主控区域,也是国家生存与发展重要的自然基础。目前,该区域生态和经济社会过程在空间上的叠加,不仅影响到资源、环境与生态等功能的发挥,而且对岷江流域乃至长江上游的生态安全和区域的可持续发展均构成严重威胁。认识和理解岷江上游植被NDVI时空变化及其地形响应机制,分析植被变化最佳地形位,可以为该地区生态环境建设提供方向指引与科学参考。综合运用遥感与GIS技术对岷江上游植被NDVI时空变化进行分析,并通过空间叠加分析详细探讨了植被NDVI时空变化对海拔、坡度、坡向与地形起伏度等地形因子的响应,结合不同植被变化类型的分布指数进一步明确了不同地形因子背景下植被变化地域分异规律,得出了不同植被变化类型最佳地形位。结果表明:(1)2000~2020年间,岷江上游地区植被覆盖良好且格局稳定,主要沿河谷地带扩散状分布约有26.62%的区域植被显著增长,仅有1.21%的区域植被显著退化;(2)植被变化趋势类型在高程、坡度、坡向与地形起伏度等不同地形位下具有显著不同的分布格局,整体而言不同地形位下面积占比波动较小,分布指数各异;(3)植被显著退化区域的最佳地形位分别为受人类活动影响的“优势”地带与受自然条件制约的“劣势”地带,植被显著增长区域的最佳地形位主要分布在海拔相对较低,而坡度、起伏度较大且为阴坡的人类聚落辐射区域。

The upper reaches of Minjiang River play important roles in resource support,ecological service,and environmental regulation.It is the soil erosion sensitive control region of the national ecological red line and an important natural basis for the survival and development of the country.At present,the spatial superposition of the ecological,economical,and social processes in this region not only affects resources,environmental,and ecological functions but also poses a serious threat to the ecological security and regional sustainable development of the Minjiang River basin and even the upper reaches of the Yangtze River.Recognizing and understanding the temporal and spatial variation of vegetation Normalized Difference Vegetation Index(NDVI) and its topographic response mechanism in the upper reaches of Minjiang River and analyzing the best topographic position of vegetation changes can provide direction,guidance,and scientific reference for ecological environmental construction in this region.In this study,the spatial and temporal changes of vegetation NDVI in the upper reaches of Minjiang River were analyzed using remote sensing and GIS technology.Through spatial overlay analysis,the response of spatial-temporal variation of NDVI to topographic factors such as elevation,slope,aspect,and topographic relief was discussed in detail.Combined with the distribution index of different types of vegetation change,the regional differentiation rule of vegetation change under the background of different topographic factors was further defined,and the best topographic position of different types of vegetation change was obtained.The results showed that:(1) vegetation coverage in the upper reaches of Minjiang River was good and stable,and approximately 26.62% of the vegetation increased significantly,while only 1.21% of the vegetation decreased significantly during 2000-2020.(2) The types of vegetation change had significantly different distribution patterns under different topographic positions,such as elevation,slope,aspect,and relief degree.Overall,the area proportion fluctuated slightly under different topographic positions,and the distribution index was different.(3) The best topographic position of the regions with significant vegetation degradation was the "dominant" zone,which was affected by human activities and the "inferior" zone,which was restricted by natural conditions.The best topographic position of the regions with significant vegetation growth was mainly distributed in the areas with relatively low elevation,large slope,and relief and shady slope of human settlement radiation.