Prediction Of Forest Net Primary Productivity And Its Climate Response Analysis In Northeast China Based On CMIP6

Forests are the most important terrestrial ecosystem on earth,storing 50%of global terrestrial carbon and absorbing about 31%of anthropogenic carbon emissions.They are an important bridge connecting the terrestrial biosphere and the atmosphere,realizing the carbon cycle,water cycle and energy exchange,and play an irreplaceable role in coping with climate change.Northeast China is located in the middle and high latitudes of the northern hemisphere,and is one of the main distribution areas of natural forests in China,with diverse forest types,including coniferous,broad-leaved and mixed coniferous forests,which play an important role in the ecosystem carbon cycle.Based on the BEPS model and InTEC model,this study simulates the net primary productivity（NPP）of forests in northeast China from 2015 to 2100under three climate models（SSP126,SSP245,and SSP585）of CMIP6,analyzes the spatial and temporal patterns of NPP of forests in northeast China under different climate scenarios and The spatial and temporal patterns and trends of NPP in Northeast China under different climate scenarios were analyzed to study the carbon sequestration capacity of Northeast China forests under different anthropogenic emission change scenarios.The climate response patterns of spatial and temporal changes of forest NPP in Northeast China under long time scales are analyzed to reveal the response mechanisms of CO₂ concentration,temperature,precipitation,solar radiation and other factors on forest carbon sequestration.This study clarifies the important role played by forest ecosystems in global climate change,and provides scientific support for the scientific formulation of policies to cope with global climate change,protect the ecological environment,rationalize the use of ecological resources and achieve sustainable development.The main findings of this paper are as follows:（1）Under all three models,forest NPP in Northeast China all showed fluctuating increasing trends from 2015 to 2100,with the largest increase in forest NPP in Northeast China under the SSP585 model and the smallest change under the SSP126 model.The interannual trends of NPP of three forest types in Northeast China under the same scenario model were all ranked in the order of magnitude of change:mixed coniferous forests>broadleaf forests>coniferous forests.（2）All three models showed significant positive correlations between forest NPP and CO₂concentration and temperature in Northeast China.Future forest NPP values in Northeast China all increased with precipitation,and the higher the scenario emission concentration,the greater the increase in NPP values.None of the relationships between forest NPP and solar radiation in Northeast China were significant.Combined with the analysis of the projected importance of variables,it was found that with the increase of low,medium and high emission scenario concentrations,CO₂ concentration gradually explained the importance of forest NPP in Northeast China more strongly than temperature,and precipitation in the three models did not explain the importance of NPP.（3）Assuming that the future human society develops according to the SSP126 scenario model,and taking the CO₂ concentration,temperature and NPP values under this model as the benchmark values,and doing correlation analysis,we found that the forest NPP in Northeast China under the SSP245 and SSP585 models both showed an increasing trend from 2015 to2100,and the magnitude of NPP change was greater under the SSP585 model.By forest type,the magnitude of NPP changes in the three forest types under SSP245 and SSP585 models were ranked as follows:mixed coniferous forest>broadleaf forest>coniferous forest.（4）The increase in NPP in both SSP245 and SSP585 models was more correlated with the change in CO₂ concentration than the change in temperature.for every 100 ppm increase in CO₂ concentration,NPP increased by 42g C·m^-2·a^-1 and 30 g C·m^-2·a^-1 in SSP245 and SSP585 models,respectively,in Northeastern forests.The response of the amount of NPP change to CO₂ concentration change for the three forest types was in descending order:mixed forest>broadleaf forest>needle forest.