巴音布鲁克高寒草原植被覆盖度时空格局及影响因素

Temporal-spatial patterns and influencing factors of vegetation coverage in Bayanbulak Alpine Grassland,China

基于MODIS NDVI数据采用线性混合光谱模型,对巴音布鲁克草原2000—2020年植被覆盖度状况进行测算,采用一元回归线性分析方法分析了其时空变化特征,以及气象、地形和土地覆被变化对区域植被覆盖度的影响。结果显示:(1)2000—2020年巴音布鲁克草原平均植被覆盖度为46.19%,总体呈西部高东部低的空间分布格局。植被覆盖度大于60%的区域分布在西北部和南部,面积占比为24.70%;植被覆盖度小于15%的区域面积占比为19.91%,分布在研究区边缘。(2)2000—2020年巴音布鲁克草原植被覆盖度呈先下降后升高的变化趋势,总体年下降速率为0.093%。像元尺度上,大部分地区植被覆盖度基本不变,呈降低趋势的面积占比为24.86%,呈面状分布在中东部和北部;呈增加趋势的面积占比为10.54%,分散分布在研究区中部和西部边缘。(3)植被覆盖度随着海拔升高逐渐降低,阳坡植被覆盖度总体低于阴坡;年降水量和年平均气温对植被覆盖度的影响具有明显的空间异质性,分别约10.70%和13.99%的地区植被覆盖度与当年降水量和上年降水量呈正相关,8.23%和11.11%的地区植被覆盖度与当年和上年平均气温呈正相关,8.23%和5.35%的地区与当年和上年平均气温呈负相关。土地覆被类型的转化,尤其是冰川和永久积雪的减少促进了植被覆盖度的变化。

Based on MODIS NDVI data,the fractional vegetation cover(FVC)of Bayanbulak Grassland was measured from 2000 to 2020 by using a linear mixed spectral model,and the spatial-temporal variation patterns were analyzed by using the linear regression method.Besides,the influence of meteorological,terrain and land cover changes on regional FVC were analyzed.The results were as follows:(1)From 2000 to 2020,the average FVC of Bayanbulak Grassland was 46.19%,which showed a spatial distribution pattern of high in the west and low in the east.Areas with FVC greater than 60%were distributed in the northwest and south,accounting for 24.70%of the total area;areas with FVC lower than 15%were distributed at the edge of the study area.(2)FVC showed a trend of decreasing first and then increasing from 2000 to 2020,with an average annual decline rate of 0.093%;on the pixel scale,FVC remained basically unchanged in most areas,and the areas with a decreasing trend accounted for 24.86%,faceted in the central-east and north,and the areas with an increasing trend accounted for 10.54%,distributed in the edge of the middle and west of the study area.(3)FVC gradually decreased with elevation,and it was generally lower on the sunny slope than that on the shady slope.The effects of annual precipitation and annually average temperature on FVC showed significant spatial heterogeneity.About 10.70%and 13.99%of the regions had a positive correlation between FVC with the current year's precipitation and the last year's precipitation,and 8.23%and 11.11%of the regions had a positive correlation between FVC with the current year's average temperature and the last year's average temperature,and 8.23%and 5.35%of the regions had a negative correlation between FVC with the current year's average temperature and the last year's average temperature.The transformation of land cover types,especially the reduction of glaciers and permanent snow cover,contributed to the change of FVC.