近65年来四川红杉径向生长对气候变暖的响应

Radial growth response of Larix mastersiana to climate warming in the last 60 years

大量研究揭示全球变暖已经对青藏高原东南缘树木生长产生显著影响,为了解气候变化对林线位置的四川特有树种四川红杉(Larix mastersiana)生长的影响,以黑水县达古冰川四川红杉为研究对象,利用树木年轮学的方法建立树木年轮宽度标准年表,探讨1977年升温突变前后四川红杉径向生长对气候因子的响应差异.结果显示,1977年后,该区域平均气温以0.304℃/10年速率呈现显著上升的趋势,而降水和相对湿度无显著变化趋势;四川红杉径向生长与生长季初期(6月)和末期(10月)及前一年秋季(10-11月)温度呈显著正相关,仅与当年1月的降水和相对湿度呈显著正相关;升温突变后,四川红杉年轮宽度指数与前一年9月和10月以及当年6月和10月平均温度和最低温度的关系由不相关变为显著正相关,而与当年3、5、10月相对湿度的关系由正相关转变为显著负相关;滑动分析结果表明四川红杉径向生长与前一年和当年10月温度仍然保持着相对稳定的显著正相关关系,未表现出"响应分异"现象,而与当年3、5、6、10月相对湿度的负相关关系随时间呈逐渐增强的趋势.因此,在未来气候变化背景下,温度升高将促进四川红杉径向生长,但相对湿度的增加将可能抑制其生长.

Numerous studies have revealed that global warming has a significant impact on tree growth in the southeastern Tibetan Plateau.However,few studies have evaluated how climate warming influences the radial growth of Larix mastersiana(LM),which is an endemic tree species in Sichuan Province,at the alpine timberline.To explore the divergent tree growth response of LM to recent climate warming around 1977 in the Dagu Glacier of Heshui County,western Sichuan Province,we used a dendrochronological method to determine tree-ring width chronology of LM and conducted growth-climate correlation analysis.Our results showed that air temperature has experienced a significantly increasing trend at a rate of 0.304°C/decade,while precipitation and relative humidity exhibited non-significant changes.Radial growth of LM was positively and significantly correlated with temperature at the beginning(June)and the end(October)of the growing season,and in autumn(October and November)of the previous year,but only positively and significantly associated with precipitation and relative humidity in January of the current year.As the temperature rose after 1977,the relationship between tree-ring width index(RWI)of LM and mean temperature and minimum temperature in September and October of the previous year and June and October of the current year increased from a non-significant correlation to a significantly positive correlation,while the relationship between RWI and relative humidity in March,May,and October of the current year changed from a positive association to a significantly negative association.The results of the moving correlation analysis revealed a relatively stable and significant positive correlation between the radial growth of LM and temperature in October of both the previous and current years,which did not exhibit"growth divergence"with abrupt warming after 1977.In contrast,a significantly negative correlation between the RWI of LM and relative humidity in March,May,June,and October of the current year showed a gradually increasing trend.Consequently,our findings indicated that rising temperature could benefit the radial growth of LM,while increasing relative humidity may hinder its growth in the context of global climate change.