Response Of δ ¹³ C To Different Climate Components Of Pinus Massoniana Tree

Tree ring is an ideal archive of paleo-climate with its characteristics of high resolution, high continuity and easily obtained duplicates. Recently, several dendroclimatology studies had been done in the subtropical area of eastern China where the climate is characterized by warm and humid condition. However, most research were based on the width rather than isotopes. It is well known that tree ring width and stable carbon isotope (δ13C) response to climate change through different mechanisms. Several studies indicated that tree ring δ13C appears to be more sensitive to the warm-wet climate change compared to width. But when it comes to δ13C, it is still unknown that the components in tree rings like whole wood, holocellulose and α-cellulose, which one is more suitable for climate reconstruction. With Masson Pine (Pinus massoniana), a tree species widely distributed in the subtropical of eastern China, this article aims at finding out the different climate sensitivity of the three components 813C and tree ring width.Tree rings were obtained from more than 35 Masson Pines in the center and south of its distribution, Jiuling Mountain and Jiulian Mountain respectively. The pretreatment imposed on tree rings including air drying, fixation and polishing. The tree ring width were measured by AcuRite with precision less than 0.001mm. Cross-dating and quality control were executed with COFECHA. Tree ring width index were calculated by ARSTAN. In each site, tree rings of four trees were selected for cellulose isolation and a13C measurement. The holocellulose and a-cellouse were isolated from whole wood referred to the method of Qian(2001).δ13C were measured by the ThermoFinniganDELTAplusXP. Lastly, RES chronology and raw δ13C series were analyzed with climate factors and the results are as follows:(1) δ13C of holocellulose and α-cellulose are isotopically enriched by 1.211±0.121‰ and 1.170‰±0.168‰ compared to δ13C of whole wood respectively. In addition, the annual variation of δ13C of holocellulose and a-cellulose are larger than δ13C of whole wood. But over all, the annual variation trend of the three time series demonstrate a high degree coherence;(2) It is quite similar for the three components of both sites that the correlations between δ13C and the relative humidity of middle-late growing season. Meanwhile, the temporal stabilities of such correlations show no significant difference. Therefore, δ13C of whole wood of Masson Pine is enough to reconstruct inter-annual relative humidity change and there is no necessary to isolate the holocellulose and a-cellulose;(3) Tree ring width of both sites are significantly positive with the average temperature of early growing season. While their relationship with the water statues of middle-late growing season are less consistency compared with δ13C of the two sites. It can be concluded that the regional temperature of winter-spring and relative humidity of summer-autumn can be reconstructed by tree ring width and δ13C respectively.