2003—2018年黄土高原植被光学厚度时空变化及其影响因素

Spatiotemporal variation in vegetation optical depth and its influencing factors over the Loess Plateau during 2003-2018

植被光学厚度(VOD)是表征地表生物量和植被含水量的关键指标,准确认知黄土高原大规模植被恢复背景下的VOD变化特征对于科学评估生态工程效益具有至关重要的作用。本文基于X波段的VODCA数据,利用趋势分析、偏相关分析和残差分析等方法,探究了2003—2018年黄土高原VOD时空变化特征,量化了气候因子和人类活动对VOD的相对贡献。结果表明:(1)2003—2018年黄土高原VOD呈显著增长趋势,增速为0.28%/10a(P<0.01),且秋季增速达到0.32%/10a(P<0.01),大于春季和夏季;(2)空间分布上,黄土高原VOD呈极显著增长区域占总面积的69.7%;减少区域仅占5.4%,且主要分布在内蒙古北部和鄂尔多斯西部;(3)黄土高原VOD与降水、太阳辐射呈显著正相关的区域主要分布在西部半干旱草原地区,负相关区域主要分布在甘肃省南部的沟壑区;(4)回归分析表明,气温、降水、辐射和人类活动对VOD的相对贡献率分别为45.74%、2.09%、38.20%和13.97%,而人类活动影响逐渐增加,其影响呈增长趋势的区域占研究区的88.4%。

The vegetation optical depth(VOD),as a crucial indicator reflecting surface biomass and vegetation water content,plays a vital role in accurately characterizing the changes in VOD under the context of large-scale vegetation restoration on the Loess Plateau.This is crucial for scientifically assessing the benefits of ecological engineering.This study,using X-band VODCA data,employs various methods including trend analysis,partial correlation analysis,and residual analysis to scrutinize the spatiotemporal variations of vegetation optical depth(VOD)on the Loess Plateau from 2003 to 2018.The research quantifies the respective contributions of climatic factors and human activities to the fluctuations in vegetation optical depth.The result indicates that:(1)The VOD on the Loess Plateau showed a significant increasing trend during the period of 2003-2018,with a growth rate of 0.28%/10a(P<0.01).Moreover,the growth rate in autumn surpassed that in spring and summer,reaching 0.32%/10a(P<0.01).(2)In terms of spatial distribution,there was a significantly increasing trend in VOD across 69.7%of the Loess Plateau,while the VOD decrease was observed in only 5.4%of the area,primarily concentrated in the northern part of Inner Mongolia and western Ordos.(3)In the Loess Plateau,the VOD showed a significant positive correlation with precipitation and solar radiation,mainly distributed in the western semi-arid grassland region.Conversely,negatively correlated regions were predominantly distributed in the gully areas in the southern part of Gansu Province.(4)Regression analysis reveals that the relative contributions of temperature,precipitation,radiation,and human activities to VOD are 45.74%,2.09%,38.20%,and 13.97%,respectively.Notably,the impact of human activities is progressively growing,encompassing 88.4%of the study area with an increasing trend.The comprehensive results of this study reveal the dynamic features of VOD changes on the Loess Plateau,offering a scientific basis for estimating vegetation carbon storage and supporting sustainable management in the context of ecological restoration on the Loess Plateau.