A Study On The Sensitivity Of Stable Carbon Isotopes Of Different Components Of Masson Pine Tree Rings To Climate Change

The tree ring plays an irreplaceable role in the global climate change research,because of high resolution,extensive sample distribution and sensitivity to environmental changes.Compared with the ring width or density and other indicators,the stable carbon isotope ratio(?13C)of tree-ring is suitable for warm and humid areas,mainly controlled by the stomatal conductance and photosynthetic rate in the leaves.However,it is difficult to obtain a uniform view on the determination that which constituent of ?13C is suitable in the study of tree-carbon stable isotope correlation,limiting the development of tree-wheel isotope climatology.The reasons for divergence of opinion may be the location of the study and the species were different.Whether it is due to the different species or the different locations cause the differences of opinion were lack of systematic research.It is possible to provide new clues to the resolution of this problem if it is possible to study the similarities and differences of the stable carbon isotopes for the different components of the same tree species in different sites.This paper takes the subtropical dominant species Pinus massoniana as an example to study the regional differences between the stable carbon isotopes and the climate,the regional characteristics of different constituents.In this study,the most widely distributed coniferous species of Pinus massoniana in the eastern subtropical region of China was chosen in six different sites to measure the ?13C of whole wood,holocellulose and ?-cellulose and to analysis the relationship with the climatic factors.The results show that:(1)The ?13C of holocellulose and ?-cellulose are isotopically enriched by 1.261±0.233 ‰ and 1.311 ± 0.189 ‰,compared to ?13C of whole wood respectively,while the ?13C of the cellulose and ?-cellulose were lack of uniformity.While ?13C is a significant correlation between the three components in different sites,there is a certain location difference between the relative coefficients.The correlation between the three components of the distribution center,the southern margin and the eastern margin of Pinus massoniana is a little higher than the western margin,the northern margin and the northern margin distribution.(2)As a whole,there are no significant differences in the correlation coefficients between the three components ?13C and climate elements in the six locations of Pinus massoniana.The ?13C of the three components are better able to respond to the effects of climate on Pinus massoniana.(3)The main climatic factors that control the ?13C of the Pinus massoniana trees in the six fields are the relative humidity in the middle and late stages of the growing season.In the area of the Pinus massoniana,the month when the ?13C increases in the summer and autumn by the high temperature and little rain is gradually late from northwest to southeast direction gradually.