宁夏荒漠草原带生态环境质量时空变化及其驱动机制

Spatiotemporal changes and driving mechanisms of eco-environmental quality in the desert steppe zone of Ningxia

生态环境质量及其变化评价是生态系统管理的关键依据,也是衡量区域生态文明建设成效的重要指标。宁夏荒漠草原带人工绿洲、旱作农田、荒漠草原、流动沙地并存,加上黄河及其沿岸湿地,山水林田湖草沙景观相对完整,是研究多种生态系统耦合生态环境质量评价的典型区域。以宁夏中部荒漠草原带为例,基于Google Earth Engine(GEE)云平台对2000—2020年Landsat地表反射率图像进行像元间优化重构,计算了区域湿度(WET)、绿度(NDVI)、干度(NDBSI)、热度(LST)四个分量指标,利用土地分类数据核算区域生态系统服务价值(ESV),通过主成分分析法将上述指标加权耦合,构建改进型遥感生态指数(IRSEI),在长时序尺度下对研究区域生态状况进行监测,并明确影响IRSEI的主要驱动因素。结果表明:(1)前两主轴累计贡献率为84.66%,其中NDVI与WET是PC1主要贡献因子;ESV是PC2的主要贡献因子。IRSEI的评价分析中引入ESV减少了分量指标在PC1的聚集现象,将分量指标分散有效反映了IRSEI的多样性。(2)研究区生态系统服务价值呈现稳步增加的趋势,其中调节服务>支持服务>供给服务>文化服务,空间上呈东北高西南低的格局。(3)2000—2020年IRSEI指数均值范围为0.546—0.598,呈现单峰型波动增加趋势,增长率为7.42%。2000—2020年,面积变化由中等与较高级为主转变为较高与高等级为主,其中高等级面积增长率达到84.79%。(4)降水是影响IRSEI分异的主要驱动因素,整体驱动因素上:降水>人口密度>温度>土地利用强度>经济生产总值。海拔则是通过影响气候因子进而间接影响了IRSEI指数。研究评价了2000—2020年宁夏荒漠草原带生态环境质量时空变化特征及驱动机制,为指导区域生态保护修复和可持续发展提供了重要决策参考。

The evaluation of ecological environment quality and its changes is the key basis for ecosystem management,and also an important indicator to measure the effectiveness of regional ecological civilization construction.The coexistence of artificial oases,dry farmland,desert grassland,and flowing inland in the desert grassland belt of Ningxia,along with the Yellow River and its coastal wetlands,presents a relatively complete landscape encompassing mountains,water bodies,forests,fields,lakes,grasslands,and sands.This area serves as a typical location for studying the evaluation of ecological environment quality within multiple ecosystems coupling.Based on the Google Earth Engine(GEE)cloud platform,this paper optimizes the reconstruction of Landsat surface reflectance images from 2000 to 2020 for the desert steppe zone of Ningxia.It calculates four component indicators of regional wetness(WET),greenness(NDVI),dryness(NDBSI),and heat(LST),and estimates the regional ecosystem service value(ESV)using land classification data.By applying principal component analysis to weight the coupling of these indicators,an improved remote sensing-based ecological index(IRSEI)is developed,which monitors the ecological condition of the study area over a long time scale,and identifies the main driving factors influencing IRSEI.The results showed that:(1)The first two principal axes accounted for 84.66%of the total variance,with NDVI and WET being the main contributors to PC1;ESV was the main contributor to PC2.The inclusion of ESV in the evaluation analysis of IRSEI decreased the clustering of component indicators in PC1,and enhanced the diversity of IRSEI by spreading the component indicators.(2)The ESV in the study area showed a steady increasing trend,with the order of regulating service>support service>supply service>cultural service.Spatially,the value was higher in the northeast and lower in the southwest.(3)The mean value of IRSEI index ranged from 0.546 to 0.598 from 2000 to 2020,showing a unimodal fluctuating increasing trend,with a growth rate of 7.42%.In the past 20 years,the area change shifted from mainly medium and high levels to mainly very high and high levels,with the high level area increasing by 84.79%.(4)Precipitation was the main driving factor affecting the variation of IRSEI,and the overall driving factors were ranked as:precipitation>population density>temperature>land use intensity>gross domestic product.Altitude affects the IRSEI index indirectly by influencing climatic factors.This study objectively assessed the spatiotemporal patterns and drivers of regional ecological environment quality in the past 20 years,and offered valuable insights for guiding regional ecological restoration and sustainable development.