贡嘎山东坡不同海拔高度树轮宽度对气候变化的响应

树木生长对气候变化的响应机制是气候重建的基础,在不同的气候或环境背景下,树轮宽度对气候变化的响应不同,其响应随着地形或海拔等因素的变化而变化。利用采自贡嘎山东坡5个海拔高度的树轮样本建立了树轮宽度年表,并对年表特征、年轮宽度及其对气候要素的响应进行分析,探讨了该区树木径向生长对气候变化的响应关系。结果表明:年轮平均宽度具有随海拔高度的增加而减小的趋势,树轮宽度对气候要素的响应也具有海拔差异。在海拔3700m的森林上限树轮宽度与当年7月份平均温度显著正相关,在海拔3000m高度与3月份平均温度显著正相关,而在海拔2800m树轮宽度与气候因子之间没有显著的响应关系。通过与海螺沟冰川末端进退变化和文献记载的特殊气候年份对比发现,树轮宽度年表与海螺沟冰川进退变化及文献记录的特殊气候年份具有一定的一致性,宽度年表对气候变化具有一定的指示意义。

Response of tree-ring width to climate change at different elevations on the east slope of Gongga Mountains

It is necessary to discover the response mechanism between tree-ring growth and climate change for climate reconstruction. The response mechanism is diverse in different climatic or environmental contexts, especially for topography or altitude. We developed five tree-ring width chronologies from sites ranging in elevation from 2800 m to 3700 m a.s.l. on the east slope of Gongga Mountains. Characteristics of the chronologies and radial growth have been analyzed. Response function was applied to discuss the relationship between tree-ring widths and the climate factors. The results indicate that rates of radial growth show a trend along with the altitudinal gradients. Climate-growth response analysis revealed that radial growth is mainly controlled by temperature. The radial growth is controlled by July mean temperature at the timberline (3700 m a.s.l.), and by March mean temperature at the 3000 m a.s.l. However, there is no significant correlation between tree-ring width and climatic factors at the 2800 m a.s.l. Compared with the documented climatic records and the fluctuations of Hailuogou Glacier, tree-ring width chronologies imply an indicative power to climate change.