Spatial And Temporal Measure And Regulation Of Land Ecological Health In Poyang Lake Ecological Economic Zone

Promoting the coordinated and sustainable development of living organisms and the natural environment is an important basis for realizing the overall layout of the“five in one”.It is the basic approach actively explored by all sectors of society to formulate differentiated and precise management and protection system by analyzing the spatial-temporal evolution law of ecosystem health level under systematic and external factors.The Poyang Lake Ecological Economic Zone is in an important development position in Jiangxi Province and even the whole country.With the rapid development of industrialization,urbanization and agricultural modernization,a series of environmental problems such as soil pollution,soil erosion and vegetation cover decline have become prominent,and explore the Poyang Lake Ecological Economic Zone land ecological health evolution law and characteristic,has become a coordinated sustainable utilization of resources and economic development contradictions are urgently needed.Therefore,this paper takes poyang lake ecological economic zone as the research object.Based on the theoretical model of PSR framework,20 indicators such as vegetation coverage,biodiversity index and human activity intensity index are selected from the aspects of natural environment,social and economic development and human activities to build the evaluation index system.At the same time,the fuzzy mathematics is introduced into the variable weight vector to correct the index weight,and the3km×3km grid is used as the research unit to evaluate the ecological health of the study area from 1995to 2015.On this basis,Moran's I index and variogram were used to measure the temporal variability and spatial differentiation of land ecological health,and the influencing factors of land ecological health were revealed.In order to better reveal the law of the evolution of land ecological health in the study area,it provides a reference for the government and administrative departments at all levels to develop precise and differentiated ecological management measures.The main results of the study are as follows:(1)The land use types in the study area are mainly forest land and cultivated land.During the study period,the area of paddy fields,dry land,forest land and grassland continued to decline,and the area of construction land continued to grow.The area of paddy field changed from 16012.22 km~2 to 15511.50km~2,the area showed a decreasing trend,the decline rate was 3.13%;the dry land area changed from4703.23 km~2 to 4509.88 km~2,the decline rate was 4.11%;the construction land area increased by 934.90km~2,the growth rate reached 68.18%.Land use change is dominated by stable maps,which is mostly concentrated in the hinterland and lakeside area of poyang lake.The phenomenon of new construction land occupying ecological land and production ecological land is common,and the contradiction between cultivated land protection,urban and rural development and ecological construction cannot be ignored.(2)From 1995 to 2015,the average EHI index of land ecological health in the study area was 0.395,0.388,and 0.410,respectively.During the 20 years,the ecological health status of the Poyang Lake Ecological Economic Zone was generally stable,and experienced the process of“degrading first and then turning good”.According to the principle of natural breakpoint method,the ecological health index value is divided into five levels of I~V.From 1995 to 2005,the area of I grade increased by 60.33%,and the area of II~V grades decreased by different extents.The area of Class II decreased by 590.22 km~2,and the area of Class III decreased from 14114.06 km~2 to 10378.02 km~2,an increase of-26.47%.The areas of grade IV degradation to grades I and II are 363.83 km~2 and 718.11 km~2,respectively,mainly in Fengcheng and Linchuan districts.The area of V grade decreased from 3050.58 km~2 to 2961.74 km~2,an increase of-2.91%.The area of V grade to grade I and grade II was 48.61 km~2 and 222.98 km~2,respectively,mainly in Yulin Reservoir area,Laoshan District and Poyang Lake area of Wuning County.Mainly due to the contraction situation,the Wanli District is completely degraded to the IV level by the V grade.From 2005 to 2015,the area of Grade I and Grade II showed a downward trend,and the area of Grade III to Grade V increased in different degrees.Among them,the area of I grade decreased by9787.14 km~2,an increase of-73.82%.The area of Grade II decreased by 3929.73 km~2,an increase of-23.94%,and the area of Class II increased to Grade III of 8514.70 km~2.The upgrading area was dominated by Duchang county,Yuyang county,Leping city and Yugan county in the eastern part of Poyang Lake;V level area increased by 982.57 km~2,growth of 33.18%.Its source is Grade III and IV,mainly appears in the lakeside area of Poyang Lake,and some areas of Guixi city have also been upgraded to Grade V.(3)In terms of spatial correlation,the EHI index of the study area is not spatially distributed,but presents a certain spatial correlation feature.From 1995 to 2015,the Moran's I values were 0.7080,0.7515,and 0.7475,respectively,and the spatial aggregation level showed an increasing trend.That is,within a certain distance threshold range,the area with high EHI value has a high eco-health index value of neighbors,and the low-value area of land use ecological risk has low eco-health index of neighbors.Spatially,each agglomeration type exhibits different diffusion and reflow characteristics.The hinterland of Poyang Lake is always in the HH agglomeration area,and it is overflowing.Nanchang City gradually evolved into a LL cluster by HH agglomeration.The area of HH type is 9954.71km~2,11507.61km~2 and10295.78 km~2 respectively.which are mainly distributed in the hinterland of Poyang Lake,Wuning county and Fuliang county in the north.In 2015,the area of HH in Guixi city increased significantly.The area of LL type is 12641.75 km~2,13676.01 km~2 and 12276.81 km~2,respectively.It is mainly distributed in the group of Gao'an city-Yushu city-Fengcheng-Linchuan district-Dongxiang county in the south,Especially in 2005,the diffusion phenomenon is obvious.By 2015,this type of area returned to the initial level of the study.(4)In terms of spatial variability,the spatial variability of the land ecological health index was the largest in 1995,followed by 2015,and the variability was the weakest in 2005.The EHI index has a positive base effect caused by random or short-distance variation,and the function simulation results are best fitted by a spherical model with a base value.The nugget values C0 are 0.00062,0.00059,and0.00059,respectively.The base values are 0.00250,0.00189,and 0.00241,respectively.The range A is3.98km,6.25km,and 5.25km,respectively.The correlation range of EHI index was controlled after a large expansion,showing an inverted V-shaped trend.The spatial variability of EHI increased gradually from southwest to northeast,which was consistent with the flow direction of Ganjiang river.(5)The factors affecting the ecological health level of land in the study area can be summarized into seven aspects:ecological integrity,food security,ecological purification capacity,disaster tolerance,economic development,population pressure and land desertification level.Among them,ecological integrity,food security,ecological purification capacity and disaster tolerance capacity have significant positive correlation with land ecological health.For each unit of the four,the corresponding increase of ecological health index is 0.031,0.013,0.005 and 0.003.Economic development,population pressure and land desertification level have significant negative correlation with land ecological health,and each of the four improves 1 unit.Eco-health index decreased by 0.014,0.007 and 0.003 per unit.From the aspects of industrial system,environmental system,resource system,cultural system and security system,the overall model of land ecological security regulation in the study area will be constructed.The typical regional regulation of each level should be based on the policy and expand the path of ecological benefits and sustainable development of economic development.