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基于新疆玛纳斯河流域2个雪岭云杉树轮最大晚材密度(MXD)年表,探讨了半干旱区MXD对气候变化的响应特征。研究结果显示,2个样点MXD年表及其区域平均年表(RC)均与7~8月平均最高气温之间呈极显著正相关关系。其中,RC与7~8月平均最高气温相关最高(r=0.54,P<0.001),并利用RC重建了7~8月份平均最高气温。重建值、观测值以及干旱指数(Is)之间的对比分析揭示,当干旱指数绝对值大于1.5σ(|Is|>2.5,1953~2008年)或连续2~3年干旱指数绝对值接近1.5σ时,水分条件将会对MXD产生影响。这一气候响应特征与研究区半干旱气候有关,在干旱年份,水分匮缺会限制晚材细胞壁的加厚,从而影响MXD。因此,与相对湿润地区相比,半干旱地区树轮MXD对气温响应的同时也会受到极端降水状况的影响,作为气温代用指标需谨慎而有限度的使用。
Based on the MXD chronology of two snow spruce tree rings in the Manas River basin in Xinjiang, the response characteristics of MXD to climate change in semi-arid regions were discussed. The results showed that there was a significant positive correlation between the two samples MXD chronology and its regional average chronology (RC) and the mean maximum temperature from July to August. Among them, RC was the highest correlated with the mean maximum temperature from July to August (r = 0.54, P <0.001), and RC was used to reconstruct the mean maximum temperature from July to August. A comparative analysis of reconstructed values, observed values and drought indices (Is) revealed that when the absolute value of the drought index is greater than 1.5σ (| Is |> 2.5, 1953-2008) or the absolute value of the drought index is close to 1.5 σ, moisture conditions will have an impact on the MXD. This climate response is related to the semi-arid climate in the study area. During drought years, water scarcity will limit the thickening of the cell walls of latewoods and thus affect MXD. Therefore, the tree-ring MXD in the semi-arid region is also affected by the extreme precipitation conditions in response to the temperature as compared with the comparatively humid regions. Therefore, it is necessary to be cautious and limited to use as a proxy for the temperature.