长白山红松和臭冷杉树轮密度变化特征及其气候响应

Variation in characteristics and climate response of tree ring wood density between Pinus koraiensis and Abies nephrolepis in Changbai Mountain

本研究建立了长白山红松和臭冷杉的全轮、早晚材密度年表,并分析了2个树种的树轮密度变化特征及其与平均气温、平均最高气温、平均最低气温和降水量的相关关系。结果表明:两树种树轮密度变化具有一致性。红松树轮密度对气候变化更加敏感,而臭冷杉树轮密度变化相对稳定。两树种树轮密度年表与平均气温和平均最低气温整体呈显著正相关,而与平均最高气温和降水量的相关性相对较弱。其中,生长季早期(4—5月)的平均最低气温可能是影响树轮密度变化的主要因素。响应面分析结果表明:随着生长季早期的平均最低气温上升,两树种早材密度与平均最低气温呈现先减弱后增强的响应趋势,而与生长季早期的降水呈现先增强后减弱的响应趋势。滑动相关分析显示:随着气候变暖,两树种树轮密度年表均对生长季晚期(9—10月)平均气温和生长季早晚期平均最低气温的正响应显著增强,而对生长季晚期平均最高气温的正相关减小,与降水的响应相对稳定。臭冷杉的树轮密度年表对上年12月平均最高气温和当年4月平均最低气温的响应出现显著的正负转换现象。

Background,aim,and scope Changbai Mountain is in the northeast monsoon region of China,a climate-sensitive and ecologically fragile area.It is also the best-preserved and largest distribution area of temperate primary forest in northeastern China.Therefore,it provides a good opportunity for tree-ring research and has received a lot of attention from tree chronology researchers.However,much of the previous research has been based on tree-ring width rather than tree-ring density.Thus,in this paper,we presented a comparative analysis of tree-ring density variation and response to climatic factors between Pinus koraiensis and Abies nephrolepis.Materials and methods We established chronologies of annual,earlywood,and latewood density in P.koraiensis and A.nephrolepis based on dendrochronological methods,and analyzed the relationships of tree-ring wood density chronologies of these two tree species with monthly mean,maximum,and minimum temperatures,and monthly precipitation based on Pearson correlation.Sliding correlations were used to detect the stability of tree-ring density changes in response to climatic factors for the two tree species.Results The A.nephrolepis density change was more stable than that of P.koraiensis,but the P.koraiensis density chronology had greater climate signal.The earlywood density chronologies of the two species were positively correlated with the mean minimum temperature early in the growing season(April—May).The response surfaces indicated that,with increased temperature,the earlywood density response to mean minimum temperature first decreased and then increased,whereas the precipitation first increased and then decreased.Sliding correlation showed that the positive response of tree ring density chronology to mean temperature at the end of the growing season(September—October)and mean minimum temperature at the early and end of the growing season significantly increased,whereas the positive correlation with mean maximum temperature at the end of the growing season decreased and the response to precipitation was relatively stable.The response of tree-ring density chronologies of A.nephrolepis to climatic factors showed a significant positive and negative conversion.Discussion Strong correlation between minimum temperatures in the early growing season and tree-ring density revealed that the minimum temperature(nighttime temperature)was the main limiting element for tree-ring density formation.A possible reason for this is that xylem cell thickening and lignification mainly occurred during the night,and higher temperatures(not exceeding the threshold temperature)resulted in more lignin accumulating in the cell wall,which increased the tree-ring density.Comparative analysis of tree-ring density chronology characteristics of P.koraiensis and A.nephrolepis in response to climate indicated that P.koraiensis was sensitive to changing climatic factors,whereas A.nephrolepis had fewer climatic signals.Continued climate warming,especially asymmetric changes in maximum and minimum temperatures,may have altered the species of live in cold and wet environment,resulting in a possible‘separation’in response to changes in A.nephrolepis tree-ring density.Conclusions The minimum temperature in the early growing season had the most significant effect on earlywood density,which indicated that the minimum temperature in the growing season may be useful for reconstructing past climate change events in the study area.The P.koraiensis tree-ring density was more sensitive to climate change than that of A.nephrolepis,and the“lag effect”in response to the previous year’s climatic factors was significantly stronger;these findings indicate that P.koraiensis is an ideal species for tree-ring reconstruction in Changbai Mountain.Recommendations and perspectives This study established P.koraiensis and A.nephrolepis tree-ring density chronology,which reflected a strong minimum temperature signal in the research area.This study will contribute to ecological studies and climate reconstruction in the future.