Dynamic Change Of Pinus Tabuliformis Forest Productivity And Its Response To Future Climate Change In Shaanxi Province,China

The fifth report of the IPCCstated that from the time of the industrial revolution to the present,the surface temperature and atmospheric CO₂ concentrations have increased to varying degrees.Almost all regions of the world have experienced different degrees of warming,and this phenomenon may continue until the end of this century.Global climate change has had a significant impact on the structure and function of ecosystems in most parts of the Earth,and this impact will continuous increase.As the main body of terrestrial ecosystems,forestsoccupy one-third of the world’s land area,and in terrestrial carbon storage,forests account for 80%of ground storage and 40%of underground storage.It can be seen that the forest ecosystem has a huge carbon sink potential.Although temperate forests only account for 8%of the land area,they take up about 40%of the carbon absorption on the land,which plays an important role in slowing global warming.Therefore,it is of great significance to study the productivity dynamics of temperate forest ecosystem and its response to future climate change.This paper takes the dominant tree species of Pinus tabulaeformis in Shaanxi Province as the research object.Through studying the climate change characteristics in this area,the response of the Pinus tabulaeformis NPP to history and future climate change and the sensitivity of P.tabuliformis to climatic factors.Based on the above research content,the following conclusions are drawn:1.Characteristics of climate change in the study areaDuring the historical period,the temperature in northern Shaanxi region,central Shaanxi region and southern Shaanxi region rose at the rates of 0.251℃·10 a^-1,0.222℃·10 a^-1,and0.21℃·10 a^-1,respectively.The temperature of different regions under different climate scenarios will increase significantly in future period,the variation range in different regions in 2015-2100 is 1.90℃³.34℃,1.79℃³.49℃,1.75℃³.44℃,respectively.Compared with the baseline period（1961—1990）,precipitation in northern Shaanxi region will gradually increased under RCP_4.5 and RCP_8.5.5 scenarios in future period,with the largest increase（14.0%）in the RCP_8.5 scenario from 2071—2100;precipitation in central Shaanxi region and southern Shaanxi region showed a decrease under different climate scenarios with the ranges of 3.6%-0.8%and 4.9%-2.8%respectively.In terms of trends,precipitation in central Shaanxi region and southern Shaanxi region will rise significantly at the rate of 15.52 and 17.58 mm·10a^-1,respectively,in 2015—2100 under the RCP_4.5 scenario.2.History and future trends of Pinus tabuliformisNPP in research areaDuring the historical period,the size of P.tabuliformis NPP showed central Shaanxi region>southern Shaanxi region>northern Shaanxi region,and the northern Shaanxi region,central Shaanxi region and southern Shaanxi region NPP were increased significantly with the rate of 26 g C·m^-2·10 a^-1,24 g C·m^-2·10 a^-1 and 16 g C·m^-2·10 a^-11 respectively.Compared with the research area NPP of P.tabuliformis forest in the baseline period,that would increase by 2%-30%in the future period,and the increasement could reach 45.4%at the end of the century（2071—2100）under RCP_8.5 scenario,under different climate scenarios,the NPP size of P.tabuliformis is RCP_8.5>RCP_4.5>RCP_2.6.During the future period,the NPP of P.tabuliformis in central Shaanxi region and southern Shaanxi region increased significantly under RCP_4.5 and RCP_8.5 scenarios;the NPP of P.tabuliformis in northern Shaanxi region decreased gradually under RCP_2.6 and RCP_4.5 scenarios with 41.00 and 21.00g C·m^-2·10 a^-1,respectively,which implied that this area has potentiality to become the carbon source.3.Sensitivity of P.tabuliformis NPP to climatic factors in the study areaThe impact of warming on the P.tabuliformis NPP in different areas was limited,and it had the greatest influence on the northern Shaanxi region.The increase of precipitation had a positive effect on the impact of NPP on P.tabuliformis in northern Shaanxi region.Compared with the changes in precipitation,the P.tabuliformis NPP of central Shaanxi region and southern Shaanxi region responded more to the temperature change.Increased precipitation will relieve the inhibitory effect of warming,with a degree of relief of northern Shaanxi region>central Shaanxi region>southern Shaanxi region.In the three regions,P.tabuliformis NPP in northern Shaanxi region was the most sensitive to climate change,and P.tabuliformis NPP in central Shaanxi region response to climate change was relatively weak.Among the 15 hypothetical climate scenarios,the most unfavorable is the T₃P₀ scenario.In this scenario,the NPP will be reduced by 11%to 22%.