Study About Carbon And Oxygen Isotopes Of Early And Late Wood In Tree Rings During The Past 215 Years In Zhangping,Fujian

Tree ring early and late wood isotopes are effective indicators for extracting seasonal climate change signals in hot and humid regions,and corresponding research work has been carried out in Fujian.However,the carbon and oxygen isotope chronology of early and late wood in Fujian has not been established.This paper selects the humid subtropical region of Fujian Province,which is sensitive to climate change and lacks related research,to establish the 215-year(1801-2015)Pinus massoniana tree ring carbon and oxygen isotopic sequence.Correlation analysis between the early-and late-wood stable carbon and oxygen isotope sequences and meteorological factors(temperature,precipitation,relative humidity,and sunshine hours,etc.)find that:(1)Sunshine hours(r=-0.468,p<0.01)and relative humidity(r=0.619,p<0.01)of Jan to May are the main limiting factors affecting the stable carbon isotope fractionation(?¹³C)of Pinus massoniana early wood,and the late wood carbon isotope fractionation(?¹³C)is mainly affected by the lowest temperature of April to July(R=-0.576,p<0.01)and the relative humidity in September-October(r=0.544,p<0.01).Relative humidity is the limiting factor for carbon fractionation throughout the growth period of Pinus massoniana and the common limiting factor for carbon fractionation of Pinus massoniana in Fujian.The mixing of early-and late-wood climate signals and the complexity of the limiting factors indicate the need for the stable carbon isotope study of early-and late-wood;(2)The stable oxygen isotope(?¹⁸O)sequence of Pinus massoniana early wood is mainly affected by the sunshine hours from January to May(r=0.538,p<0.01)and the relative humidity from April to May(r=-0.571,p<0.01),the stable oxygen isotope(?¹⁸O)sequence of late wood is mainly affected by the sunshine hours(r=0.582,p<0.01)and relative humidity(r=-0.533,p<0.01)from July to October,both early-and late-wood reflect relative humidity and sunshine hours information.By comparison,it is found that the?¹⁸O sequence of late wood has the potential to replace the entire round of?¹⁸O sequence for climate analysis,but it may not be as good as the tree ring?¹⁸O sequence analysis for the capture of climate limitation factors on a longer time scale(such as across the second half of the year).By reconstructing the relative humidity of January-May and July-October from 1821 to 2015 of study area respectively and representing the hydro-climatic conditions of the spring rain period and monsoon period in South China,the analysis found that the synergistic changes between the two on the interannual scale are not stable and may be affected by El Ni?o-Southern Oscillation(ENSO)variability regulation;on the interdecadal scale,the driving mechanisms of the two are also different,the hydrological climate in spring rain in South China is affected by the Atlantic Multidecadal Oscillation(AMO),and the monsoon period hydrological climate is regulated by the Asian Pacific Oscillation(APO).