| As a typical river basin in Three Gorges Reservoir area,Daning River Basin(DNHB),dominated by the forest ecosystem,plays an important role in water purification,water yield,soil retention and water conservation,carbon storage,organic matter production,and other ecosystem services.DNHB is the ecological barrier area in the upper stream of Yangtze River,and even the entire Yangtze River Basin.Important ecological conservation tasks have been undertaken since the impoundment of Three Gorges Reservoir.In the past 20 years,policies of returning farmlands to forests and ecological conservation have been implemented continuously,and the coverage of regional forestlands have increased rapidly in DNHB.However,whether this rapid conversion to forest ecosystem can simultaneously increase the benefits of ecosystem services still lacks quantitative assessment.Therefore,a clear idea for drawing the line of the ecological function importance and managing the future land cover and ecosystem in DNHB can be obtained by analyzing the land use and land cover change(LUCC)process.It identifying major habitat evolution patterns,developing evolution trends,assessing the functional quality of ecosystem service,and determining the trade-offs between ecosystem services and LUCC in Daning River Basin in the past 20 years.Based on the above analysis and remote sensing,meteorological,soil,and environmental data,we analyzed 20 years of LUCC and habitat succession in DNHB by using the Markov transfer matrix.The ecosystem carbon storage,water yield,soil retention and NPP of the land cover in the basin were assessed using InVEST and CASA models in terms of the important change nodes in 2010.In accordance with assessment results,the trade-offs among different land use/cover types in patch scales and sub-watershed scales were analyzed to quantify the overall benefits of ecosystem services,obtain the trade-offs between ecosystem service and LUCC,establish different management patterns based on ecological benefit areas.It predict the future function change trends of ecosystem services,and provide the selection basis for land cover and ecosystem management on a forest scale in DNHB.The main research results and findings are as follows:(1)A topographic correction method(CR method)was developed to remove the envelope from remote sensing images,while the land use/cover classification map of DNHB obtained using this method passed through Kappa testing(0.8654)satisfied the remote sensing mapping requirements.The effectiveness of the topographic CR method in removing the envelope and the shadows of remote sensing images in complex terrains was verified.The process of LUCC in DNHB in the past 20 years was quantitatively analyzed.From 1995 to 2000,land use and land cover conversion was based on a natural process with minimal human intervention.From 2000 to 2005,the LUCC process was characterized by logging,reclamation,and agricultural development.From 2005 to 2010,the process of returning farmland to forest characterized the LUCC process.From 2010to 2015,the LUCC process was characterized by the continued process of returning farmland to forest with construction land reclamation and new centralized residential areas.In the past 20 years,changes in forest,cultivated,and grasslands have dominated Land use/cover in the research area,and peak changes occurred in 2010.Habitat evolution,including the five modes of flooding,artificial replacement,positive vegetation succession,negative vegetation succession,and artificial positive succession,in the past 20 years of DNHB was described.The overall evolution trend is positive and characterized by the positive succession of a large area of vegetation,and succession changes from 2005 to 2010 are the most significant.(2)With the aid of the terrain corrected CASA model,the accuracy of the assessment of the net primary productivity of mountainous vegetation was further improved.The inVEST model can evaluate the ecosystem carbon storage,water yield,Soil retention and NPP of the land use and land cover in the basin.Evaluation results:The total carbon storage was 14085.72×10~4 t,and the average carbon density was 251.48t/hm~2.The total water yield was 838.47×10~6 m~3,and the unit water yield was 1281.98 m~3/hm~2.The water conservation depth was 150.80mm.The total soil retention is 65.23×10~4 t,and the unit soil retention is 116.46 t/hm~2.The total NPP is 941.44×10~4t,and the unit NPP is 1559.27g/m~2·a,In 2010 of DNHB,respectively;(3)The trade-offs of ecosystem services in DNHB indicated a synergistic effect in37.16%of regional ecosystem services and a trade-offs effect in 62.84%of regional ecosystem services in 2010.The overall synergistic degree in the basin was low,and the main trade-offs were concentrated between the carbon storage/organic matter production and water conservation/soil retention,with the following specific research results.On a patch scale,the overall benefits(OB)and the coefficient of variation(CV)of ecosystem services in the upper stream at the north and east of the basin were in the high-value area with sharp trade-offs and dominated by the broad-leaved and mixed forests.This outcome was mainly caused by the steep slope terrains,poor hydrothermal conditions,and relatively poor water conservation and soil retention capacities.The OB and CV of the ecosystem services in the lower stream at the center and south of the basin were in the low-value area with relatively low trade-offs mainly because of flat terrains and frequent human disturbances.On a forest scale,the trade-offs results of ecosystem service benefits were classified according to different forest types:broadleaf forest(BF)>conifer and broadleaf forests(CBF)>other forests(OF)>conifer and conifer forests(CCF)>conifer forest(CF)>broadleaf and broadleaf forests(BBF)>bamboo broadleaf(BB)>loosened forest(LF)>shrubbery forest(SF).Based on this sorting result,the forests land use and land cover management model for DNHB was defined.On the basin scale,the ecological service management zones in DNHB were divided into spatial units for forest resource management and regulation based on the comprehensive benefit analysis results of forest ecosystem services.The main ecosystem service provision capacity and the comprehensive service benefit spatial characteristics as indicators.Then,the research area was divided into four key land use/cover management areas,namely,high-value,sub-high-value,sub-low-value,and low-value areas of ecological service comprehensive benefits according to discrete spatial characteristics of the ecosystem service supply capabilities and comprehensive benefits of the four land-covered resources.The management methods for all areas were defined,and the division results were used as the red lines for defining the ecological functions in the research area.(4)Based on the above analysis results,multiple scenarios of LUCC in DNHB were established.According to the Logistic–CA–Markov model,the natural growth,ecological protection,ecological agriculture,and ecological construction scenarios were established to simulate the spatial distribution of land use and land cover in the research area in 2030.According to the changes in land use/cover under different scenarios,the trade-offs results showed significant differences in ecosystem service functions under different scenarios.Policy makers should consider the relationships among organic matter production,water yield,and soil retention services in selecting future regional development scenario strategies to maximize the ecosystem service benefits in the basin and provide decision-making and regulation ideas for the management of the land and ecological resources in DNHB. |
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