生态补水前后永定河两岸植被覆盖度变化及驱动力分析

Analysis of Fractional Vegetation Cover Changes and Driving Forces on Both Banks of Yongding River Before and After Ecological Water Replenishment

植被是生态系统的重要组成部分,在能量交换、水土保持、防风固沙等方面具有重要作用。为了研究生态补水对永定河两岸植被覆盖度的变化的影响,基于Landsat-8卫星影像数据,利用影像图差值比较法、皮尔逊相关系数、残差分析等方法对永定河生态补水前后植被覆盖度时空变化及其驱动力进行分析。结果表明,(1)2014—2020年永定河两岸植被覆盖度总体上呈现西北高、东南低的分布格局,植被覆盖度变化呈现优化趋势,改善区域面积大于退化区域面积。(3)植被覆盖度与年气温的平均相关系数为−0.17,与年降水量的平均相关系数为0.15。植被覆盖度总体上与气温呈负相关,与降水量呈正相关,但具有显著性(P<0.05)的面积分别仅占23.03%和16.26%。(4)生态补水前,人类活动对植被覆盖度的影响主要是负面影响,而在生态补水后,人类活动对植被覆盖度的影响逐渐向好,发挥正面影响的面积占比63.04%。2014—2020年期间人类活动变化的趋势向促进植被覆盖度增长的方向发展。(5)气候变化和人类活动对于植被覆盖度改善和轻改善区域相对贡献在60%以上的面积占比分别为16.98%和68.09%,人类活动对于植被覆盖度变化的影响更大,整体上对于植被覆盖度的增长具有积极作用。(6)永定河区域水面面积七年增长约100.07%,与植被覆盖度均值变化趋势一致,呈现“升—降—升”的变化规律,且它们之间的相关系数可达0.83(P<0.05),呈显著正相关。综上所述,2014—2020年永定河两岸植被覆盖度整体呈现改善趋势,气象因素对其影响较不显著,生态补水对植被覆盖度的增长具有显著相关关系。

Vegetation is one of important parts in ecosystem and plays an essential role in energy exchange,water and soil conservation,wind protection and sand fixation.In order to reveal the influence of ecological water replenishment on fractional vegetation cover changes and its driving forces,this study analyzed the Landsat-8 satellite image data through image difference comparison,Pearson correlation coefficient,and residual analysis.The results showed that(1)from 2014 to 2020,fractional vegetation cover on both banks of Yongding River presented distribution pattern of high in the northwest and low in the southeast,respectively.The fractional vegetation cover variation showed an optimization trend,where the improved area was larger than the degraded area.(3)The average correlation coefficient between FVC and annual air temperature and annual precipitation was−0.17 and 0.15,respectively.In general,FVC was negatively correlated with air temperature and positively correlated with precipitation.The negative and positive correlations(P<0.05)were significant in the area only accounting for 23.03%and 16.26%,respectively.(4)Before ecological water replenishment,the impact of human activities on fractional vegetation cover was mainly negative,which,however,was reversed after ecological water replenishment with the improved area reaching up to 63.04%.During 2014 and 2020,human activities promoted the growth of fractional vegetation cover.(5)The relative contribution(>60%)of climate change and human activities to FVC improvement and light improvement areas were 16.98%and 68.09%,respectively.Human activities had a greater impact on the FVC change and had a positive effect on the FVC growth.(6)The water surface area of Yongding River region increased by about 100.07%in the past seven years,consistent with the change trend of the average fractional vegetation cover,showing a“rise-fall-rise”changing pattern.The correlation coefficient between water surface area and fractional vegetation cover was up to 0.83(P<0.05).In conclusion,the fractional vegetation cover on both banks of Yongding River showed an overall improvement trend during 2014−2020.The growth of fractional vegetation cover had a significant correlation with the ecological water replenishment but not with meteorological factors.