Response Of Carbon Cycle Of Typical Natural Secondary Forest And Plantation To Climate Change In Shaanxi Province

In recent years,due to the climate warming,the reduction of snow cover and glacier area,the rise of average sea level and the frequent occurrence of extreme natural disasters,people have realized the seriousness of the problem of climate change.The long-term climate change will undoubtedly have a serious impact on the terrestrial ecosystem.As the main body of the terrestrial ecosystem,forest plays an important role in mitigating climate change and reducing atmospheric carbon dioxide concentration.Therefore,it is of great significance to understand how the forest ecosystem responds to future climate change.In this study,Shaanxi Province was selected as the research area,and the typical local artificial forest?Robinia pseudoacacia forest?and natural secondary forest?Quercus spp.forest?were selected as the research objects,and the process-based dynamic vegetation model LPJ-GUESS was used to simulate the dynamic changes and trends of net primary productivity?NPP?,net ecosystem productivity?NEP?and soil heterotrophic respiration?Rh?in the historical and future period of the two forest ecosystems,in order to provide scientific basis for the sustainable management and management of forest in Shaanxi Province under the condition of climate change.The main conclusions are as follows:?1?It has been verified that the LPJ-GUESS model can well simulate the dynamic changes and trends of NPP,NEP and Rh of Robinia pseudoacacia forest and Quercus spp.forest in Shaanxi Province;?2?In the historical period,the NPP of Robinia pseudoacacia forest and Quercus spp.forest in the study area increased slowly at the rate of 1.7—10.0 g C?m^–2?10 a^–1 and 4.8—17.0 g C?m^–2?10 a^–1,respectively,and the range of NPP of the two forests was between-0.9%—1.4%.In the future,NPP of both forests will increase with the increase of climate emission intensity.Compared with the base period,NPP of Robinia pseudoacacia forest and Quercus spp.forest will increase by 12.2%—55.1%and 12.3%—57.8%respectively.From the perspective of the whole province,climate change makes the forest ecosystem productivity higher in Middle Shaanxi?MSX?and Southern Shaanxi?SSX?with humid climate.The climate environment tending to warm and dry in the future may be the main factor limiting the increase of forest NPP in Northern Shaanxi?NSX?;?3?In the historical period,the two kinds of forests in the study area showed smaller carbon sink.Compared with the base period,the NEP of Quercus spp.forest and Robinia pseudoacacia forest decreased by 1.8%—2.4%and 1.5%—2.7%respectively.In the future,the NEP trend of Robinia pseudoacacia forest under three RCP scenarios is greater than that of Quercus spp.forest,so the carbon sink potential of Robinia pseudoacacia forest is higher under the future climate change.From the perspective of the whole province,in the future,the NEP of two kinds of forests in NSX will decrease by 0.9%—93.6%,which is a large carbon source.Therefore,it is necessary to strengthen forest ecosystem management and maintain and improve the carbon sink capacity of forest ecosystem under the future climate change.While,the NEP of two kinds of forests in MSX and SSX will increase by 0.3%—56.6%,and the forest ecosystem will show carbon sink;?4?In the historical period,Rh of the two kinds of forests in the study area is shown as SSX<MSX<NSX.The Rh of the two kinds of forests increased slowly,with an increase of 1.5%—5.5%.In the future,Rh value of Quercus spp.forest is greater than that of Robinia pseudoacacia forest.From the perspective of the whole province,the Rh of the two forests will increase significantly at the rate of 11.0—42.0 g C?m^–2?10 a^–1 under the three RCP scenarios in the future.Compared with the benchmark period,the Rh of the two forests will increase by 30.0%—47.9%in NSX,and increased by 39.8%—77.1%in MSX and SSX in the future.