关键词: 大兴安岭, 早材, 晚材, 樟子松, 稳定碳同位素, 树轮

Abstract:

Aims We assess the relationship among the carbon isotopic signatures of earlywood (EW), transitional wood (TW) and latewood (LW) from tree rings. Our aims were to investigate variation in the intra-annual stable carbon isotope ratio (δ ¹³C) in Pinus sylvestris var. mongolica and determine the relationship between them and homologous ring width. Methods Based on two tree discs of Pinus sylvestris var. mongolica sampled from the northern part of Daxing’an Mountains in China, the EW, TW and LW were obtained with different stripping and pooling programs. After performing ring widths measurement and cross-dating, the periods analyzed were the maximum growth periods for one sample and different growth periods for the other. The holocellulose fractions were extracted and the intra-annual δ ¹³C of samples were measured. Important findings In general, the δ ¹³C values of TW are the highest, EW come second and LW are the lowest. The intra-annual trend of δ ¹³C is fluctuateing prominently from the juvenile period to the fast-growing period and is smoother from the maturation period to the senescence period. The variation amplitude of LW is almost greater than EW at the same period. The δ ¹³C of LW is always prominently higher than EW for the juvenile period. The difference between EW and LW is indistinctive for the maturation period and is negligible for the senescence period. The intra-annual variability of δ ¹³C concentrates on the middle and later phase of the growing season. The correlation relationship between the intra-annual δ ¹³C sequences and homologous detrended ring width sequences (dRWS) decreases with the seasons, which implies that environmental factors play a dominant role in cell formation and carbon fractionation during the middle and later phase of the growing season in each year. The ring width of EW of the current year is positively correlated with LW of the previous year (pLW). Also the δ ¹³C of EW is negative correlated with the incorporative dRWS of EW + pLW. But the correlation between δ ¹³C of EW and δ ¹³C or dRWS of pLW is statistically insignificant. The growing season could be divided as: EW (from late April to middle June, with greater soil moisture and rapidly increasing temperature), TW (from late June to middle July, with lower soil moisture and maximum temperature) and LW (from late July to middle September, with greater soil moisture and decreased temperature).

Key words: Daxing’an Mountains;, earlywood, latewood, Pinus sylvestris var. mongolica, stable carbon isotope, tree rings