| The Three Gorges Reservoir Area is the ecological security protection area in the Yangtze river basin,and also as the national important ecological barrier area,important eco-function area for soil and water conservation,biodiversity,main functional area for ecological conservation and restoration,and the key area of forestry ecological projects.The Three Gorges Reservoir Area is an ecologically sensitive and fragile area.Since 2000,the construction projects of Grain for Green Project and sheltering forests of the Yangtze river have been continuously implemented in the Three Gorges Reservoir Area,and significant changes have taken place in land use,which have lead to changes to local ecosystem servicesLanlingxi watershed,Maoping town,Zigui county,Hubei,as a representative pilot of the Three Gorges Reservoir Area,which included specialized in the national demonstration of Grain for Green Project was research area was the research areaLand use change.ecosystem service functions change(water conservation,soil conservation,carbon storage and water purification),and response of ecosystem service function to land use change were analyzed with observed data of corresponding meteorology,water quality,geography and land use/cover change before and after Grain for Green Project from national positioning observation station of forest ecosystem in Zigui,Yichang,Hubei province Time scale were before and after conversion of farmland to forests,and spatial scale were protection forest along the river at low altitude(<375m),economic forest at middle altitude(375～800m),ecological welfare forest at high altitude(>800m).Conclusions are as follows:(1)The Lanlingxi watershed covered an area of 1527.43 hm2.In 1999,farmland area was 497.65 hm2 and covered 32.58%of the watershed,while the the area of tea and citrus covered less than 2%.In 2017,the proportion of farmland fell to 4.16%because most of farmland was replaced by tea,citrus and frutex.The tea area increased to 296.47 hm2 and covered 19.41%of the watershed,while citrus covered 3.47%,and frutex covered 4.68%.of the watershed.Land use conversion was from farmland to tea,citrus and frutex.At the protection forest along the river,farmland was the main land use in 1999,while in 2017,tea area covered 29.53%which was at first place,and the proportion of farmland dropped to 8.37%.In 1999,at economic forest,the area of coniferous forest was in first place,farmland was next with proportion for 28.68%.In 2017,the area of coniferous forest had nearly no change,and the proportion of tea increased to 18.88%which took the second place,while the proportion of farmland was less than 4%.At ecological welfare forest,coniferous forest was the main land use befor and after the project,proportion for 97.87～97.95%,without significant change.(2)In 1999,ecosystem service function per unit area were as follows:water conservation for 612.79 mm,soil conservation for 415.08 t/hm2,carbon storage for 77.91 t/hm2,nitrogen output for 3.77 kg/hm2,phosphorus output for 0.42 kg/hm2.In 2017,ecosystem service function per unit area were as follows:water conservation for 759.45mm,soil conservation for 493.64 t/hm2,carbon storage for 96.89 t/hm2,which were higher than 1999 for 23.81%,18.93%,24.37%Nitrogen output for 2.65 kg/hm2,phosphorus output for 0.22 kg/hm2.which were less than 1999 for 29.69%,46.88%.After returning farmland to forests,the ability of water conservation,soil conservation,carbon storage and water purification of Langlingxi watershed ecosystem were improved.In 1999,farmland was the main land use at protection forest along the river,ecosystem service function per unit area at this altitude were as follows:water conservation for 449.39 mm,soil conservation for 357.26 t/hm2,carbon storage for 53.60 t/hm2,nitrogen output for 4.84 kg/hm2,phosphorus output for 0.69 kg/hm2.There were many coniferous forest at economic forest,ecosystem service function per unit area at this altitude were as follows:water conservation for 596.13 mm,soil conservation for 449.39 t/hm2,carbon storage for 72.98 t/hm2,nitrogen output for 3.61 kg/hm2,phosphorus output for 0.38 kg/hm2.The proportion of coniferous forest at cological welfare forest was beyound 97%,and ecosystem service function per unit area at this altitude were as follows:water conservation for 789.91 mm,soil conservation for 503.78 t/hm2,carbon storage for 113.40 t/hm2,nitrogen output for 2.63 kg/hm2,phosphorus output for 0.14 kg/hm2.In 2017,at protection forest along the river,ecosystem service function per unit area at this altitude were as follows:water conservation increased 43.95%,soil conservation increased 28.56%,carbon storage increased 48.65%,nitrogen output decreased 24.17%,phosphorus output decreased 49.28%.At economic forest,ecosystem service function per unit area were as follows water conservation increased 31.41%,soil conservation increased 19.82%,carbon storage increased 20.84%,nitrogen output decreased 21.05%,phosphorus output decreased 47.37%.At cological welfare forest,ecosystem service function per unit area were as follows:water conservation increased 13.02%,soil conservation increased 15.17%,carbon storage increased 9.30%,nitrogen output decreased 10.00%,phosphorus output decreased 7.14%After returning farmland to forests,with the decrease of farmland area and the increase of tea,citrus,frutex,the ability of water conservation,soil conservation,carbon storage and water purification of the ecosystem were improved.The local ecological environment had been effectively improved with Grain for Green Project.The assessments of land use/cover change and ecosystem service function change in the study area can be used for constructive suggestions provided for the ecosystem protection in the study area,committed to rational development of land resources,promote the progress of the Grain for Green Project,and realize the sustainable development of regional society,economy and ecosystem. |
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