喀斯特断陷盆地景观生态风险演变及其地形分异

Evolution of landscape ecological risk and its topographic differentiation in Karst Fault Basin

景观生态风险评价是构建区域生态安全格局的关键途径。以喀斯特断陷盆地为研究对象,从自然、社会、景观格局三个维度选取11个评价因子构建景观生态风险评价指标体系,通过空间主成分分析的方法评价研究区2000—2020年的景观生态风险时空演变格局,并基于地形位指数系统揭示喀斯特断陷盆地景观生态风险与地形的关系。结果表明:(1)2000—2020年,喀斯特断陷盆地的景观生态风险水平整体呈下降趋势,生态环境整体好转。(2)景观生态风险的变化呈现出较强的时空异质性,南部更甚。2000和2005年,研究区高、较高景观生态风险区主要分布于研究区北部和南部部分地区;2010年及其以后,高风险区面积显著减少,低风险区面积显著增加,但南部个别区县的风险水平未明显改善。(3)20年间,除建设用地外,不同土地利用类型的生态风险水平均显著降低。到2020年,耕地、林地、草地均主要分布在风险水平较低的区域,而建设用地在高风险区的面积仍高达43.43%。(4)景观生态风险在不同地形位梯度的变化随时间推移有显著差异。研究初期,各风险区对地形的选择性较强,低、较低风险区在中、低地形位区间的分布优势较强,高风险区倾向分布在高地形位区间;随时间推移,不同等级风险区对地形的选择性减弱,地形对景观生态风险的影响逐渐减小,人类活动对景观生态风险的影响日益凸显。

Under the dual background of the acceleration of urbanization and the requirement of sustainable development,people are paying more and more attention to regionally ecological security.In this context,landscape ecological risk assessment could evaluate the regionally ecological environment from the perspective of landscape pattern and ecology,and it is a crucial way to construct regionally ecological security pattern.Previous attempts to evaluate landscape ecological risk mainly focused on land use and the calculation of landscape index,overlooking the impact of topography.The Karst Fault Basin is located in the middle and upper reaches of the Pearl River and the Yangtze River,with complex topography and fragile ecological environment.Here,taking the Karst Faulted Basin as the research object,we selected 11 evaluation factors from three dimensions of nature,society and landscape pattern to construct an evaluation index system of landscape ecological risk.The factors′weights were determined by spatially principal component analysis(SPCA)and mathematical statistics,and the spatio-temporal evolution pattern of landscape ecological risk in the study area from 2000 to 2020 was evaluated.Furthermore,based on terrain niche index derived from Digital Elevation Model(DEM),the topographic distribution indices of each ecological risk grade in the study area from 2000 to 2020 were calculated,and the relationship between landscape ecological risk and topography in the Karst Faulted Basin was systematically revealed.The results showed that:(1)from 2000 to 2020,the landscape ecological risk level of the Karst Faulted Basin presented a downward trend,and the overall level of ecological environment improved.The change of landscape ecological risk demonstrated strongly spatial and temporal heterogeneity.In 2000 and 2005,the landscape ecological risks in the study area were mainly medium,relatively high and high,and concentrated in the north and some parts of southern study area.After 2010,the area of high risk region decreased significantly,while the area of low risk region increased significantly.However,the landscape ecological risk level of some southern districts and counties showed a trend of rising instead of decreasing.(2)The landscape ecological risk levels of different land use types decreased significantly except for construction land in past 20 years.In 2020,the cultivated land,forest land and grassland were mainly distributed in areas of low and relatively low risk level,while the area of construction land in high risk regions was still as high as 43.43%.(3)The changes of landscape ecological risk in different topographic gradients presented significant differences over time.At the early stage of the study period,all risk areas had strong terrain selectivity.Low and relatively low risk regions were mainly distributed in the middle and low terrain intervals,and high risk areas tended to be distributed in the high terrain intervals.As time went by,the topographic selectivity of different risk regions declined,indicating that the impact of terrain on landscape ecological risk gradually decreased,and the influences of human activities on landscape ecological risk became increasingly obvious.Our analysis can provide a reliable scientific basis for optimization of landscape pattern,ecological protection decision and further development and construction of the Karst Fault Basin.