祁连山南坡主要河谷NDVI时空变化及影响因素分析

Temporal and spatial variations of NDVI and analysis of influencing factors in main valleys of southern slope of Qilian Mountains

为进一步保护祁连山生态环境及合理开发利用河流沿线的植被资源,该文基于MODIS数据的NDVI产品及DEM数据集,对祁连山南坡主要河流谷地2000—2018年植被生长季的NDVI时空分布特征进行了研究,并提取研究区的主要地形因子,分析其对河流谷地植被生长季NDVI的影响。结果表明:随着河流两侧缓冲区距离逐渐增大,各年份的NDVI值呈现先增加后平稳再减少的分布特点;2000—2018年研究区河谷NDVI的变化趋势基本一致,整体表现出2010年出现了近20年的峰值;祁连山南坡河流谷地NDVI值,从斜坡(16°~25°)至急坡(41°~45°)增加的速率最大,说明该区间为NDVI值突变区间。2000—2018年祁连山南坡主要河流谷地的NDVI时空分布,可能受地形、气温和降水等自然因素影响较大,其受人为干扰因素影响较小,其中降水并非影响研究区河谷植被NDVI分布的主导因素,而气温可能是影响研究区河谷植被NDVI分布的主导因素。在地形因子中,存在较适合植被生长的特定坡度区间,且太阳辐射能量的增加有利于植被的生长。

In order to protect the ecological environment of the Qilian Mountains and utilize the vegetation resources along the river,the spatial and temporal distribution characteristics of NDVI in the main growing valleys of the southern slope of Qilian Mountains on the vegetation growing season from 2000 to 2018 based on the NDVI products and DEM datasets of MODIS data,and extracts the main topographic factors of the study area was analyzed.The results were as followes:With the increasing distance of buffers on both sides of the river,the NDVI values of each year showed increase first and then level off and then decreased.The trend of NDVI was basically same and the peak of the past 20 years appeared in 2010 in the study area from 2000 to 2018.The NDVI value of the river valley increased from the slope(16°-25°)to the steep slope(41°-45°)in the southern slope of the Qilian Mountains,indicating that the interval is the NDVI value mutation interval.The spatial and temporal distribution of NDVI may be affected by natural factors such as topography,temperature and precipitation,which were less affected by human disturbance factors,and the precipitation did not affect the NDVI distribution,and temperature may be the dominant factor affecting the distribution of NDVI in the valleys of the southern slope of Qilian Mountains from 2000 to 2018.Among the topographic factors,there was a specific slope interval that suitable vegetation growth,and the increase of solar radiation energy is beneficial to the growth of vegetation.