祁连山中部青海云杉上下限树轮宽度年表对气候的响应差异

Response of tree-ring to the climate factors at upper and lower elevation in the middle region of Qilian Mountains

通过建立和比较祁连山中部青海云杉(Picea crassifolia)生长上限和下限的树轮宽度指数年表,发现青海云杉年表的平均敏感度(M.S.)、样本量的总体解释信号(EPS)、第一主分量(PCA1)、和标准差(S.D.)以及信噪比(SNR)都表现出上限小于下限的规律。相关分析结果表明在森林下限,青海云杉的生长主要受降水的限制,而上限处青海云杉生长的限制因素不明确,并不是单一的降水或温度;通过对上下限年表做窗口为31年的逐年滑动相关后发现,青海云杉下限年表之间的相关性比较稳定;而上限年表之间的相关性有显著差异,这可能是由于随时间变化上限年表所包含气候信号不同所致。

Based on the cores of Qinghai spruce （ Picea crassifolia） from upper and lower limit of tree growth in middle region of Qilian Mountains, we developed the tree -ring width index standard chronologies. The results showed that characteristics of chronology had more climatic information, and tree - ring width of lower limit was significantly and positively correlated with the precipitation in last year. There was no remarkable consistency between treering width curve of upper limit and the mean temperature or precipitation in weather data recorded during 1960 -2008. According to the reconstructed precipitation series and the 31 -year sliding correlation, theresults show that the correlation coefficients of standard chronologies at lower limit maintained at a relatively sta- ble level, and that of upper was consistent with the precipitation changes on low - frequency. So the different climatice response of upper and lower elevation limits of Picea crassifolia growth may be primely caused by the upper chronologies containing different climate signal.