| In recent years,with the gradual implementation of “Grain for Green” and natural forest protection projects,great changes have taken place in land use.Under the background of climate change,clarifying the temporal and spatial characteristics of land use and evaluating its impact on ecosystem services could meet the assessment needs of ecological benefits of “Grain for Green” and natural forest protection projects.At the same time,it is of great significance to improve the efficiency of regional land use and ecological protection and give full play to the basic supporting role of land resources in the construction of ecological civilization.Therefore,aiming at the problems of poor vegetation and fragile ecological environment in Zhushan county,land use type maps,meteorological data,Landsat and MODIS remote sensing images in 1980,1995,2000,2005,2010 and 2015 and forest resources survey satellite remote sensing image in 2009 and other data in Zhushan county were selected for the study.The temporal and spatial characteristics of different land use types,and the net primary production,soil and water conservation and carbon storage services and the relationship among land use,landscape index,meteorological factors and ecosystem services were studied by field investigation,model calculation and statistical analysis.Main conclusions are as follows:(1)In Zhushan county,the land use structure was relatively stable in recent 35 years,and land use area showed a trend of forest land > cropland > grassland > water area > built-up land.During the study period,forest land,cropland and grassland all showed a two-way conversion equilibrium situation while the process was slightly different.Specifically,the area of forest land decreased.The area of cropland increased first and then decreased.The change of grassland area was not significant,and just decreased slightly as a whole.The water area and built-up land showed an increasing trend year by year,approaching a sub-extreme non-equilibrium situation.The conversion of cropland and forest land was strong.Grassland was mainly converted into water area and built-up land,while water area and built-up land were mainly expanded by occupying cropland and forest land.(2)At class level,landscape pattern showed the regular characteristics of increasing the dispersion degree,fragility and fragmentation degree,and decreasing the connectivity of landscape.In 2010-2015,the phenomenon of forest land patch merging was prominent.The spatial expansion type of plantation changed from outlying type to edge-expansion type,and the filling type gradually increased.At landscape level,the patterns in the study area tended to be fragmented and heterogeneous.(3)The linear change trend of NDVI showed spatial heterogeneity.The rising trend in the southern mountainous area was more obvious than that in the northern mountainous area,and the central plain showed a downward trend.The significant trend of vegetation change was as follows: significant improvement(49.19%)> slight improvement(42.39%)> basically unchanged(5.70%)> slight degradation(2.70%)> significant degradation(0.02%).(4)NPP showed an upward trend on the inter annual scale,but the growth rate was lower than the national average rate.The distribution of NPP is axisymmetric with the highest average NPP in July,and NPP from June to August was higher than other months.The spatial distribution pattern of NPP in different periods was different,but the overall trend was the same,decreasing from the north and south to the central region.The impact of human activities on NPP was mainly manifested in two aspects.On the one hand,it was the positive promotion under the policies of “Grain for Green” and natural forest protection projects;on the other hand,it was the negative loss impact caused by occupying forest land,cropland and grassland in the process of urbanization.(5)The spatial distribution pattern of soil erosion and carbon storage remained basically stable.The high-value areas were mainly in forest land while the low-value areas in the relatively broken areas in the middle of the study area.In terms of temporal changes,the amount of soil erosion in Zhushan county showed a trend of decreasing first and then increasing and then decreasing in recent 35 years.This trend was closely related to precipitation and reservoir construction.Besides,“Grain for Green” and natural forest protection projects played an important role in the reduction of soil erosion.The carbon storage had been reduced and the loss is serious,which was closely related to the urban expansion directly occupying forest land,cropland and other ecological land.(6)The main factors influencing soil conservation and carbon storage were different.Soil conservation was mainly affected by AI,LPI and ED,and carbon storage was mainly affected by LSI,ED and AI.There was a significant negative correlation between IJI and soil conservation and carbon storage,and a significant positive correlation between LPI and soil conservation and carbon storage(P = 0.002).There was no consistent correlation between CONTAG and soil conservation and carbon storage,which may be related to the scale effect of landscape index on ecosystem services. |
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