Research On Land Use And Cover Change And Its Ecological Environment Effects In The Northern Agro-pastoral Ecotone

With the development and utilization of land resources intensified,the structure and function of natural ecosystems are disturbed and destroyed in varying degrees,the ecological environment changes and hinders regional health and sustainable development.It has important practical and realistic significance for the sustainable utilization and ecological security of regional land to study regional Land Use and Cover Change,and its ecological environmental effects.The typical northern agro-pastoral ecotone such Guyuan County was took as the research object in this paper,the LUCC data of comprehensive regional natural and cultural information was the main line,and“3S”technology was the main means,the quantitative relationship between land use change and ecological environment effect was built through the establishment of the landscape stability index model and the ecological service value evaluation model,in order to realize the sustainable development of regional land,comprehensive qualitative and quantitative research was carried out to provide scientific basis for the rational use of land resources,landscape pattern optimization and land renovation,and provide important theoretical basis and practical guidance for the ecological environment construction of the northern agro-pastoral ecotone.The main results are as follows:(1)Spatio-temporal evolution of LUCCThe area of cultivated land and grassland accounted for more than 83%of the total area of the study area,which constituted the landscape matrix of the study area.From 2000to 2015,the annual average growth rate of land use types showed:Grassland>Building>Woodland>Bare-land,the annual average decreasing rate of land use types showed:Water>Farmland>Saline-alkali land.The comprehensive land use dynamic degree increased from 0.79%in 2000—2010 year to 0.86%in 2000—2015 year,this showed that the quantity,structure,mode and intensity of land use in the research area have been further changed with the progress of economic development and urbanization.The comprehensive index of regional land use degree was between 335 and 350,indicating that the level of land use development was high,and the amount and change rate of land use degree wear less than 0 during the whole period of study,indicating that the comprehensive utilization level of land resources in the study area was in the period of adjustment.The conversion among farmland,grassland and woodland was relatively frequent,in which the roll out of farmland was greater than that of change over to farmland,while the grassland and woodland wear increased by 342.42 km~2 and 9.97 km~2 respectively,and the main roll in source was farmland,indicating that the project of"Returning Farmland to Woodland and Grassland"has achieved good results.The implementation of the project of returning farmland to forest and grassland has achieved good results.From2000 to 2015,29.87 km~2 farmland,10.29 km~2 grassland and 10.11 km~2 bare-land were transformed into building land,leading to the building land expansion,at the same time,8.37 km~2 water was converted to grassland and bare-land with the expansion of vegetable planting area and the increase of water consumption,eventually lead to the area of water area was decreasing and the area of bare-land was expanding during the whole study period.(2)Evolution of LUCC landscape patternFrom 2000 to 2015,about farmland landscape and woodland landscape,the PD and AI index decreased,while the index PAFRAC and LSI increased,indicating that the fragmentation degree of farmland and woodland decreased,but the distribution of farmland and woodland tended to disperse and the stability decreased.About grassland landscape,the index of MPS,AI,LSI and COHESION showed a continuous increase in addition to the decreasing trend of PD index,which indicated that the fragmentation degree of grassland was gradually weakened and distributed more centrally,the distribution of grassland was more concentrated,the stability is strengthened,at the same time,the internal connectivity of grassland was strengthened,and the edge effect is significantly improved,this allowed full play to positive ecological environment effect of grassland.About building landscape,the MPS and AI index was increasing,the PD and the PAFRAC index was decreasing,indicating that the construction land tended to expand continuously,and gradually realized the development trend of scale and agglomeration.About bare-land landscape,the MPS index increased,the index of PD and PAFRAC continued to decrease,this indicated the bare land has formed a joint effect,and the bare-land had relative rule geometry,which indirectly indicated that human activity was an important reason for the enhancement of desertification in the study area.The scale of water landscape decreases,and the geometry of patches tended to be irregular and complicated.From 2000 to 2015,in landscape-level,the index of SHDI,SHEI and CONTAG in the study area was increasing,and the index of DI and PD declined continuously,indicating that the diversity and uniformity of the landscape spatial distribution wear enhanced,the landscape dominance was weakened,while the fragmentation degree was reduced,and distribution was more concentrated,and connectivity was enhanced.(3)The ecological environment effect of LUCCThe spatial differentiation of landscape stability in the study area was obvious,Jiulian Cheng,Fengyuan Dian and Lianhua Tan,this three towns had high stability,and their stability index average value wear 0.879,0.817 and 0.776,while the landscape stability index of the No.2 Hui Township was only 0.000 2.From 2000 to 2015,the landscape stability of 12 townships in 16 towns in Guyuan county showed an upward trend,indicating that the overall landscape stability in the study area was constantly improving,but there were still some towns with poor landscape stability and the landscape stability index in these towns showed a continuous decline.In the ecosystem service value,the ecological service value of farmland occupied absolute advantage,and accounted for more than 44%of the total ecosystem service value in the whole research period.The contribution rate of water unit area to the ecological service value of Guyuan was 25353.27 yuan/hm~2,the increase and maintenance of water area was beneficial to the improvement of ecological service value,especially for the strengthening of regional support service and regulating service function.(4)The research results showed that the spatial structure,transformation direction and organization form among the land use types in the study area had been optimized continuously,which had a positive impact on the increase of regional stability,and the overall ecological environment quality of the region is improved.While the stability of the study area was increased,the value of landscape ecological service was reduced by 5.43×10~7 yuan,indicating that with the optimization of the spatial pattern,the ecological service function of the landscape was not necessarily enhanced,there is also a need to strengthen the protection of water and wetlands for the further exertion of regional ecosystem services.