基于土地利用变化的黄河流域景观格局及生态风险评估

Landscape pattern identification and ecological risk assessment using land-use change in the Yellow River Basin

黄河流域生态环境脆弱,水土流失严重,诊断其景观格局及生态风险对促进流域高质量发展具有重要意义。该研究采用黄河流域2000、2010和2018年的土地利用数据,计算景观格局指数并构建生态风险评价模型,从网格尺度和县域尺度揭示生态风险的时空演化特征和空间关联性。结果表明:1)草地和耕地面积之和占黄河流域总面积的70%以上,2000—2018年,耕地面积减少14243 km^(2),未利用地面积减少9410.3 km^(2),建设用地面积增加12179.8 km^(2)。2)2000—2018年,黄河流域斑块数、斑块密度、最大斑块指数、景观形状指数、香农多样性指数值上升,蔓延度指数值下降,黄河流域景观格局趋于复杂化、破碎化和分散化。3)2000—2018年,黄河流域的生态风险值呈上升趋势,较高风险区和高风险区的面积增加,低风险区和较低风险区的面积大幅度减少,生态风险等级大多由低等级向高等级转移。4)2000—2018年,黄河流域生态风险呈现空间正相关,但空间聚集程度和空间分异性减弱。网格尺度的Moran’s I指数大于县域尺度,表明网格尺度的空间正相关性更强。基于上述结果,该研究将黄河流域划分为生态风险重点管控区、严格管控区和一般管控区,并提出差别化的管控建议,以期为流域管理及风险防控提供定量参考和决策依据。

Ecological risk assessment is essential to the diagnosis of the adverse environmental factors as a result of human activities for the decision-making in risk management.Since the Yellow River Basin of China has a fragile ecological environment and serious soil erosion,this study aims to analyze its landscape pattern and ecological risk factors for a better control of impact sites,and the sustainable development of agricultural production.First,the index of landscape pattern was calculated using the land-use change data on the Yellow River Basin in 2000,2010 and 2018.Then,an assessment model of ecological risk index(ERI)was constructed using the index of landscape pattern,thereby exploring the spatial and temporal characteristics of ecological risks.The transfer laws of ecological risks were set at the grid scale(1078 grid units divided by ARCGIS)and county scale(391 county-level units divided by administrative regions).Finally,the Moran’s I and a local indicator of spatial association(LISA)were selected to clarify the spatial correlation of ecological risks.The research results show that:1)The grass land and cultivated land were the main types of land-use area,accounting for more than 70%of the total area in the Yellow River Basin.From 2000 to 2018,the area of cultivated land had decreased by 14243 km^(2),and the area of unused land had decreased by 9410.3 km^(2),while the area of construction land had increased by 12179.8 km^(2).It infers that the Yellow River Basin was still in a period of rapid urbanization during this stage,where the rigid demand was strong for construction land.2)Most indicators increased,including the number of patches,patch density,largest patch index,landscape shape index,and Shannon diversity index,whereas,the splitting index had decreased in the Yellow River Basin from 2000 to 2018.The overall landscape pattern tended to be complex,fragmented,and decentralized.Specifically,the forest land and cultivated land showed the highest fragmentation,and the grass land and cultivated land had the most complex landscape shapes and structures.3)There was an upward trend of the maximum ecological risk,increasing from 0.62 to 0.74 from 2000 to 2018.The higher-risk and high-risk areas continued to increase,and the low-risk and lower-risk areas were greatly reduced.Ecological risk levels mostly shifted from low to high levels.The most shifted areas on the grid scale were from low-risk areas to medium-risk areas(119437 km^(2)),and the most shifted areas on the county scale were from medium-risk to higher-risk areas(123095 km^(2)).4)The Moran’s I of ecological risk was greater than 0 from 2000 to 2018,showing a positive spatial correlation.But there was a downward trend of Moran’s I,indicating that the spatial aggregation and spatial differentiation of ecological risks were weakened.The Moran’s I on the grid scale was larger than that on the county scale,indicating that the grid-scale ecological risk had a stronger spatial positive correlation.There was a decreasing trend in the number of"high-high"and"low-low"agglomeration units,indicating that the local spatial aggregation of ecological risks decreased.Some recommendations were made on the differentiated management,where the key,strict,and general control areas were divided without crossing municipal administrative regions.The finding can provide a potential insightful reference for the prevention and control of ecological risks,and thereby promote the high-quality development of the Yellow River Basin.