宁夏沿黄城市带植被覆盖度时空变化及驱动力分析

Spatiotemporal Changes and Driving Force Analysis of Vegetation Cover in the Urban Belt Along the Yellow River in Ningxia

宁夏沿黄城市带位于黄河中上游,是宁夏的人口和经济中心,定量分析该区域植被覆盖度(FVC)的时空分布特征及其驱动因子,对于推动黄河流域生态保护和高质量发展先行区建设具有重要意义.利用Landsat系列卫星遥感数据,基于像元二分模型反演了2001~2020年宁夏沿黄城市带FVC,分析了其空间格局和时空变化特征,并结合该地区同期气象、地形和土地利用等数据,采用Sen+Mann-Kendall趋势分析、Hurst指数和参数最优地理探测器模型对其驱动因素进行分析.结果表明:①时间上,2001~2020年宁夏沿黄城市带FVC总体呈现显著增加趋势(P<0.01),增长速率为0.25%·a^(-1),多年FVC均值为33.38%,总体植被处于较低水平;空间上,宁夏沿黄城市带FVC具有显著的地域差异,整体上呈现出“东北高西南低”的趋势,类型以极低植被覆盖度和低植被覆盖度为主.②20年间,宁夏沿黄城市带植被状况得到明显改善,植被覆盖度改善区域面积占比为62.60%,远大于退化区域的面积,FVC平均变异系数为0.098,整体稳定性较好.③FVC的H值小于0.5的区域占66.15%,表现出较强的反持续性;FVC呈改善趋势的面积占比为34.84%,持续稳定不变的区域面积占7.8%,呈退化趋势的区域占52.9%,有9.0%的区域的FVC未来变化趋势不确定.④驱动因子分析表明,土地利用类型是影响宁夏沿黄城市带植被覆盖度空间分布的主要因子;各因子交互作用的解释力(Q值)均高于单因子,表现出双因子协同增强和非线性增强关系,不存在独立关系;各驱动因子对研究区植被生长的影响均有其适宜的范围.

The urban belt along the Yellow River in Ningxia,located in the middle and upper reaches of the Yellow River,serves as the population and economic center of Ningxia.Quantitatively analyzing the spatiotemporal distribution characteristics of the fraction of vegetation cover(FVC)in this region and its driving factors is of great significance for promoting ecological protection and the construction of a leading area for high-quality development in the Yellow River Basin.In this study,Landsat satellite remote sensing data were utilized to derive the vegetation cover from 2001 to 2020 in the cities along the Yellow River in Ningxia using a pixel-based binary model.The spatial pattern and spatiotemporal changes were analyzed.Additionally,meteorological data and topographic information for the same period in this region were combined.Sen+Mann-Kendall trend analysis,Hurst index,and parameter-optimized geographical detector models were used to analyze the driving factors.The results indicated:①From 2001 to 2020,there was a significant overall increasing trend in vegetation cover in the urban belt along the Yellow River in Ningxia(P<0.01),with a growth rate of 0.25%per annum.The 20-year average FVC was 33.38%,and the vegetation cover was at a relatively low level.In terms of spatial distribution,the vegetation was high in the northeast and low in the southwest,and the main types were very low vegetation coverage and low vegetation coverage.②During the 20 years,the vegetation condition of the urban belt along the Yellow River in Ningxia had been significantly improved,and the portion of the area with improved vegetation cover accounted for 62.60%,which was much larger than that of the degraded area,and the average coefficient of variation of FVC was 0.098,which was good for the overall stability.③The area with H value of FVC less than 0.5 accounted for 66.15%,which showed strong anti-continuance,the area of FVC with improving trend accounted for 34.84%,the area of continuously stable and unchanged area accounted for 7.8%,the area with degrading trend accounted for 52.9%,and the future trend of FVC was uncertain in 9.0% of the area.④The analysis of driving factors revealed that land use type was the primary factor influencing the spatial distribution of vegetation cover in the urban belt along the Yellow River in Ningxia.The explanatory power(Q value)of interactions among various factors was higher than that of individual factors,demonstrating synergistic and nonlinear relationships among them,with no independent relationships.Risk detection showed that each driving factor had its appropriate range for impacting vegetation growth in the study area.