Vegetation Productivity Modeling Response To Climate Change In Shitouhe River Basin Of Qinling Mountains Based On BIOME-BGC Model

Climate change and elevated CO₂ concentration,as direct factors to change plant growth conditions,affect plant growth and development process and water cycle process,and have a significant impact on total primary productivity,net primary productivity and net ecosystem productivity of vegetation.The research on dynamics and response of vegetation productivity under the background of climate change has obvious theoretical and practical significance.Qinling Mountains,as an important geographical dividing line in China,has an obvious response of vegetation growth to climate change.Previous studies focused on the spatial and temporal distribution characteristics of vegetation growth and carbon cycle of ecosystem in Qinling Mountains by using mathematical statistical models and remote sensing estimation models,and lacked research on the long-term response of vegetation productivity to climate change,which is not conducive to the time-longitudinal analysis of the impact of climate factors on vegetation productivity.In this paper,Biome-BGC model was used to simulate the dynamic changes of productivity of five vegetation types in the Shitouhe River Basin of Qinling Mountains from 1959 to 2016.Based on the correlation analysis between vegetation productivity and climatic factors,the response of vegetation productivity to climate change was explored.Through the comparative analysis of simulation results of future temperature,precipitation and atmospheric CO₂ concentration under different scenarios,the intensity of the unit climate factor variation on productivity is estimated.On the other hand,the downscaling meteorological data in the Qinling region were selected to predict the productivity of vegetation types in the early,middle and late stages of this century.In addition,the sensitivity of model parameters in the study area was preliminarily discussed.The results show that:?1?The annual average vegetation productivity?GPP,NPP,NEP?of temperate deciduous broad-leaved forest was 1136.67,638.02 and 30.89 g C m^-2a^-1,the average vegetation productivity of evergreen coniferous forest was 880.69,362.38 and 39.85 g C m^-2a^-1,the average vegetation productivity of deciduous coniferous forest was 501.56,328.59 and31.24 g C m^-2a^-1,the average vegetation productivity of alpine shrub was 687.92,203.74and 15.02 g C m^-2a^-1,and the average vegetation productivity of alpine meadow was306.36,179.41 and 38.62 g C m^-2a^-1,respectively.Overall,the interannual variation characteristics of productivity of different vegetation types are basically the same in the past 58 years.GPP and NPP show a slight upward trend in fluctuation,among which the upward trend of GPP is stronger than that of NPP,and NEP keeps stable in fluctuation.?2?The responses of annual GPP,NPP and NEP to annual temperature,precipitation and CO₂ concentration were different among different vegetation types.The responses of GPP,NPP and NEP to monthly temperature,monthly and previous monthly precipitation were also significantly different.?3?In the future,the overall increase of temperature,total precipitation and CO₂concentration will affect the growth of vegetation productivity in the study area.The overall increase of temperature,total precipitation and CO₂ concentration will be 1?,5%and 50?mol·mol-1,which will lead to the increase or decrease of GPP,NPP and NEP in different vegetation areas.The positive and negative effects of GPP,NPP and NEP are also different.?4?In the early,middle and late stages of this century,GPP and NPP of deciduous broad-leaved forest showed a progressive decline trend,NEP remained stable,GPP and NPP of other vegetation types increased gradually,NEP was basically stable;vegetation productivity showed the characteristics of high in summer and low in winter,NEP showed the characteristics of"positive in summer and negative in winter",summer months were mostly"carbon sink"months,and winter months were mostly"carbon source"months.?5?The parameters of Biome-BGC model,such as C/N ratio of leaves,C/N ratio of fine roots,fraction of leaf N in Rubisco,carbon distribution of new fine roots and leaves,showed high sensitivity under the vegetation types in the study area.Annual turnover rate of standing trees,C/N ratio of fine roots,fraction of leaf N in Rubisco were positive influential parameters,such as C/N ratio of leaves,maximum stomatal conductance,new fine roots.Carbon partition ratio with blade was a negative parameter.