毛乌素沙地植被NDVI动态及对降水的多时空响应

Changes in NDVI and its multiscale spatiotemporal responses to precipitation in the Mu Us Desert

毛乌素沙地生态环境脆弱,理解沙地植被-降水关系对沙地生态有效恢复和“以水定绿”至关重要。本文基于多尺度降水和NDVI数据,研究了2000—2018年毛乌素沙地植被动态变化及其对降水时滞与累积效应的响应关系。结果表明:(1)2000—2018年研究区沙地植被年均和季均NDVI总体均呈显著增加趋势(P<0.01),且增加趋势的空间分布差异性较大;夏季NDVI显著增加的区域达83.2%,年均NDVI显著增加的区域仅占34.15%;(2)沙地植被NDVI的年际变化和月变化对降水的响应均无显著时间滞后,但存在显著时间累积效应;约38.58%的区域ND-VI年变化对降水的累积响应时间为1a和2a,且集中分布在年均降水量较少的区域;(3)生长季季节NDVI与累积月降水相关系数的时空分布差异明显。春季、夏季和秋季NDVI对降水的累积响应时间和占比分别为2~3个月(19.25%),4个月(73.58%),1个月(27.22%)或3个月(34.91%)。本研究揭示了毛乌素沙地植被对降水的响应并无显著时滞效应,而时间累积效应在研究区不同时空尺度上均表现出明显差异。研究结果为优化人工固沙植被的生态恢复方案以及实施“以水定绿”策略提供了有力的科学依据。

The Mu Us Desert possesses a delicate ecological environment.It is therefore of utmost importance to understand the correlation between sand-fixing vegetation and precipitation to achieve effective ecological resto-ration and implement the concept of“water-oriented greening”in the desert.This study examined the fluctuation patterns in vegetation within the Mu Us Desert from 2000 to 2018,as well as its reaction to delayed and cumula-tive precipitation effects.Our findings revealed significant trends in the annual and seasonal average NDVI of the study area from 2000 to 2018(P<0.01).However,the spatial distribution of these trends exhibited substantial variation.Notably,the region with a significant increase in summer NDVI accounted for 83.2%of the total area,whereas the region with a significant increase in annual NDVI accounted for only 34.15%of the total area.More-over,the annual and monthly variations in vegetation NDVI showed no significant time lag in response to precipi-tation,but a significant cumulative effect was observed.Approximately 38.58%of the study region exhibited a cu-mulative response of NDVI to precipitation lasting between one and two years,which was mostly concentrated in areas with lower annual precipitation and negligible changes in annual NDVI.Finally,the spatial and temporal distribution of the correlation coefficient between seasonal NDVI and cumulative monthly precipitation exhibited pronounced differences.The response time and percentage of NDVI to precipitation varied across seasons,with a range of 2-3 months(19.25%)for spring,4 months(73.58%)for summer,and either 1 month(27.22%)or 3 months(34.91%)for autumn.This study revealed the absence of significant temporal delays in the vegetation re-sponse to precipitation in the Mu Us Desert.Additionally,it revealed that the cumulative effects varied signifi-cantly across different spatiotemporal scales.Consequently,the findings of this study serve as a foundation for op-timizing ecological restoration programs involving artificial vegetation,as well as implementing the“water-based greening”approach.