| Chengde’s transitional region from the plateau to the plain belongs to the transition zone from semi-arid to semi-humid and the typical agro-pastoral interlaced zone.With the influence of global climate change,human activities and natural disasters,this region had experienced a series of environmental problems such as land desertification,land degradation,biodiversity decreasing sharply and water shortage,which have disrupted the balance and stability of the ecosystem and aggravated the contradiction between human society and ecological environment,hindering the regional sustainable development and ecological civilization construction.Therefore,Chengde’s transitional region from the plateau to the plain was taken as the study to construct the regional ecological vulnerability assessment system based on the Ecological Sensitivity-Ecological Resilience-Ecological Pressure(SRP)model.The Ecological Vulnerability Index(EVI)of the region from 2000 to2020 was calculated using spatial principal component analysis method,and continue with standardization processing.The results were divided into slight(0 ≤ EVI < 0.2),mild(0.2 ≤EVI < 0.4),moderate(0.4 ≤ EVI < 0.6),severe(0.6 ≤ EVI < 0.8),and extreme(0.8 ≤ EVI ≤1.0)for spatial presentation using the Arc GIS software.Analyze land types and regional vulnerability levels in combination with land use types and regions(Weichang Manchu Mongolian Autonomous County,Fengning Manchu Autonomous County and Longhua County),and assess the ecological vulnerability in different periods based on the comprehensive ecological vulnerability index(CEVI).The mutual transformation and center of gravity transfer direction of different vulnerability levels were analyzed based on the transfer matrix and center of gravity transfer model,and analyzed the impact of single factors and inter-indicator that influence the spatial distribution ability and function types using the geographic detector model.At the same time,net primary productivity of vegetation is used as an evaluation indicator to use the feature ranking in machine learning algorithm to extract Erdaoying Village,Sanfuxing Village and Taolu Village three villages for vulnerability verification.From the above researches,the following main conclusions were drawn that:(1)Based on the principles of scientificity,comprehensiveness,operability,and dynamism in ecological vulnerability assessment,the ecological vulnerability assessment system for Chengde’s transitional region from the plateau to the plain was constructed by selecting elevation,slope,terrain undulation,average annual temperature,average annual precipitation,soil erosion intensity,normalized vegetation index,biological abundance index,population density,and GDP density.(2)The overall spatial distribution of ecological vulnerability in Chengde’s transitional region from the plateau to the plain shows an increasing trend from northwest to southeast.The ecological vulnerability degree of cultivated land,forest land,grassland,and unused land was mainly the moderate and severe,construction land is mainly the severe and extreme,and watershed was mainly the severe.The ecological vulnerability of Weichang Manchu Mongolian Autonomous County was mainly the moderate,Fengning Manchu Autonomous County was mainly the moderate and severe,and Longhua County was mainly the moderate and extreme.(3)During the period from 2000 to 2020,the ecological vulnerability degree of Chengde’s transitional region from the plateau to the plain was mainly moderate and severe,and mainly shifted from severe to moderate,accounting for 12.05%.Since 2010,the ecological environment in the region has been continuously improved.The ecological vulnerability degree includes slights,mild,moderate,severe,and extreme,with the overall shift of the center of gravity moving towards the east(104.09 m),southeast(164.09 m),southwest(117.67 m),northeast(149.27 m),and southwest(224.00 m)directions,respectively.The overall shift of the ecological vulnerability center of gravity moving towards the southwest direction,and migration distance was 372.46 m.(4)The annual average temperature,elevation and soil erosion intensity were the main driving factors affecting the spatial distribution of ecological vulnerability in Chengde’s transitional region from the plateau to the plain.The normalized vegetation index,elevation,slope and population density were the four factors with the strongest ability affecting the net primary productivity of vegetation in Sanfuxing Village.The four indicator factors with the strongest ability affecting the net primary productivity of vegetation in Taolu Village were normalized vegetation index,soil erosion intensity,elevation and slope.The four indicator factors with the strongest ability affecting the net primary productivity of vegetation in Erdaoying Village were elevation,population density,GDP and normalized vegetation index. |
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