Estimation And Prediction Of Net Ecosystem Productivity In Urban Scale Based On Remote Sensing Technology

The impact of human activities on the carbon cycle has largely contributed to global climate change,but also via climate feedbacks on natural carbon sources and sinks.Net Ecosystem Productivity is a key component of terrestrial carbon cycle.According to NEP,the sustainable development ability and the health of the ecosystem can be analyzed and evaluated.As a traffic location in the north and south of China,Xuzhou is an important node city of "One Belt,One Road",as well as an important coal producing area and North China power base.However,with the development of economy,mineral resources are depleting,land use and land change(LULC)is changing dramatically,the scale of building land is multiplied and transportation system is growing rapidly,Xuzhou has to faced the dilemma of urban transformation.The regional ecological environment has also suffered tremendous pressure of sustainable development simultaneously.Taking downtown Xuzhou as an example,based on remote sensing and geographic information technology,this paper analyzed the evolution of LULC and landscape pattern estimated NEP over 2001-2016 years.Considering the high spatial heterogeneity of urban scale,the Net Ecosystem Productivity(NPP)estimation model of urban scale is established,and then predicts its future development trend of LULC and NEP by historical data of LULC and NEP.Main methods and conclusions in this dissertation are as follows:First,the area of Construction Land in downtown Xuzhou doubled;Farmland and Forest showed a significant downward trend;the Grassland area was larger and the growth was more significant;and the Unused Land showed a fluctuating downward trend.Construction Land is mainly concentrated in the western part of the study area,and gradually spread to the east and south;cultivated land is mainly distributed at the edge of the Construction Land,with the expansion of the Construction Land,Farmland range gradually degenerates from the central city to the edge;the Water was distributed in the west,south and southeast of the study area.However,Unused Land gradually shifted from the western part of the study area to the eastern and southern regions.Second,in terms of urban landscape pattern.At the type level,Farmland changed significantly,NP increased,plaque area decreased,fragmentation significantly increased,NP of Construction Land increased,but the increase of plaque area was more significant.At the landscape level,LPI increases and NP increases significantly,but CONTAG,SPLIT and the aggregation index(AI)decrease,and DIVISION was significantly increased,which indicated that the landscape fragmentation and heterogeneity of the study area were enhanced and the connectivity was reduced.Third,Net Ecosystem Productivity.NEP of downtown Xuzhou in the 2001-2016 showed a first decline after the rise,the overall significant decline in the trend,of which the significantly reduced area was mainly distributed in the central part of the study area,the south of the study area and the northeast,the significantly increased area was small,and the distribution was more fragmented.Most areas in the downtown Xuzhou were in a largely unchanged state.In addition,the low-value areas of NEP were mainly distributed in the old town west of the study area,and was expanding to the east gradually,the high value of NEP was mainly distributed in the marginal areas of the study area where are Farmland,Forest and other areas.Forth,changes in land cover have led to significant changes in NEP.Due to changes in land cover,there have been significant changes in NEP,which the changes in land types that have a particularly significant impact on NEP have Grassland,Construction land and Water.Further analysis of the relationship between NEP and landscape pattern shows that the fragmentation,heterogeneity,connectivity and separation of landscape patterns were closely related to NEP,and with the fragmentation of landscape pattern,the increase of heterogeneity and separation,and the decrease of connectivity,NEP would be reduced to a certain extent.Fifth,based on the ARIMA model and the grey prediction model,the NEP in downtown Xuzhou has been predicted.According to the relative error,the effect of ARIMA model was better than that of GM.The results of prediction models showed that the NEP in the future shows a relatively stable state,but NEP value was in the low value region.