| The surface on the Loess Plateau is filled with gullies,which are vertical and horizontal,and the phenomenon of soil erosion is corresponding serious.In recent years,the policy of returning farmland to forests h as been gladly,willingly and readily implemented of long standing on the Loess Plateau by the government,which has significantly improved the quality of the regional ecological environment by reinstating the vegetation.During the steady,enduring,and progressive procedure of watershed vegetation restoration,ecosystem services as water conservation,soil conservation,and carbon storage in the watershed have been substantially enhanced.Whether there are differences among the concomitant ramifications of vegetation restoration on ecosystem services in different regions on the Loess Plateau,and whether there are trade-offs and synergies relationships between different ecosystem services,are related to both extent and scope of ceilings on regional vegetation restoration and watershed management strategies in future.In this study,three typical watersheds in the Loess Plateau were initially selected:Huangfuchuan,Dalihe,and Yanhe watersheds;subsequently the characteristics of vegetation restoration in different watersheds were conducted by combing the regional watersheds with remote sensing interpretation and precipitation data at five-year intervals from 1990 to 2015.Afterward based on the In VEST model,the variations of carbon storage,soil conservation,and water conservation functions under the influence of vegetation restoration in the study area were evaluated.Conclusively,exploring the trade-offs and synergistic relationships among distinct ecosystem services in the watershed scale and proposing strategies for vegetation restoration in dissimilar regions are of great significance for the sustainable development and ecological protection of the Yellow River Basin.The main conclusions reached are as follows:(1)The research areas are listed from north to south,Huangfuchuan watershed,Dalihe watershed,and Yanhe watershed,of which the regulatory areas of utilized types of land use in urbanization in Huangfuchuan watershed is very small,and the transfer changes between different land use types in the watershed is not obvious during 1990-2015.In the Dalihe watershed,throughout the same period,the areas of cultivated land and unused land have decreased apprantly,the areas of forest land and construction land have obviously increased,further more the comprehensive constructions of the Dalihe watershed are better than Huangfuchuan watershed.The scale of the yanhe watershed is relatively large.In the past 25 years,the area of cultivated land in the watershed has decreased notably,and the areas of woodland and grassland have increased significantly.From 1990 to 2015,the average NDVI indexs of vegetation in three watersheds in the above sequence range from 0.32-0.65,0.36-0.73,and 0.49-0.81,seperately.During 25 years,the research peridod,the NDVI index of the entire region showed an increasing trend as a whole,with an average increase of more than 0.12,while precipitation,annual average temperature and NDVI in the study area all showed increasing trends.According to the results of M—K test,precipitation and air temperature in the region did not change significantly,while NDVI value showed a significantly increasing trend There is a significant positive correlation between the precipitation and the average NDVI,and there is no significant positive correlation between the annual average temperature and the average NDVI.(2)Comparing the assessment of the ecosystem services in the three watersheds in the research area,combind the distribution of ecosystem services within each watershed,the carbon storage in the Huangfuchuan watershed,Dalihe watershed,and Yanhe watershed respectively showed an increasing trend.The amounts of carbon storage among the districts are followed the consecutive order below:Yanhe Watershed>Huangfuchuan Watershed>Dalihe Watershed;The soil conservations in selected watersheds are in an increasing trend from north to south,however,the increaseing amount is in the order:Yanhe Watershed>Dalihe Watershed>Huangfuchuan Watershed.Meanwhile the water conservations in study areas are slightly different.It shows a decrease trend in the Huangfuchuan watershed and an increase trend in the Dalihe watershed,but the water conservation in the Yanhe watershed shows a trend of increasing firstly and decreasing later.The results of water conservation in the basin was closely related to the precipitation.The status of water conservation of the three watersheds in the research region is comply with the following rule:Yanhe Watershed>Dalihe Watershed>Huangfuchuan Watershed.In 2015,with an increase of NDVI in the three watersheds in research area,it had a positively impact on the ecosystem services of the watershed(3)There is a positive correlation between carbon storage and soil retention in Huangfuchuan watershed,Dalihe watershed,and Yanhe watershed,that is,the two of ecosystem service are in a synergistic relationship;However,there is a negative correlation in group of carbon storage and water conservation,and in soil conservation and water conservation,namely,the these two groups of services are in trade-offs;It is concluded that the trade-off relationship among the three services of carbon storage,soil conservation and water conservation in the study area is followed the below rule:Yanhe Watershed<Dalihe Watershed<Huangfuchuan Watershed,while the relationship of comprehensive benefit value is Yanhe Watershed>Dalihe Watershed>Huangfuchuan Watershed.From 1990 to 2015,the trade-off between carbon storage and water conservation in the study area decreased,while the comprehensive benefits increased.In summary,from 1990 to 2015,land use/land cover changes of the three watersheds in Huangfuchuan,Dalihe,and Yanhe was mainly due to the increasing areas of forest land and grassland,and the decreasing areas of cultivated land.The improvement of the ecological environment in each watershed has led to a positive development of the ecosystem service.However,there is a certain degree of trade-offs between the carbon storage,soil conservation and water conservation in the study area,which has an adverse effect on the sustainable development of ecosystem services in the watershed.Therefore,the future development stratgies of the watershed should continue to carry out on ecological protection to ameliorate the ecosystem stability of the three watersheds in Huangfuchuan,Dalihe and Yanhe. |
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