树轮宽度记录的额尔齐斯河上游地区过去291年的降水变化

利用采自额尔齐斯河上游6个采点的西伯利亚云杉(Picea obovata Ledeb)树轮样本建立了区域树轮宽度年表。与气候要素的相关分析表明,该地区树木径向生长主要受降水制约,区域树轮宽度年表与富蕴气象站上年7月至当年6月的降水总量相关显著。在此基础上建立了转换方程,重建了额尔齐斯河上游地区1722—2012年上年7月至当年6月的降水总量,方差解释量高达55.1%(调整自由度后为54.2%)。重建结果显示,该地区过去291年间存在9个降水偏多的时期和8个降水偏少的时期。降水重建序列还存在2.1a和3.2a的显著周期及2.3、21.6、24.3a的较显著周期,并且在1876—1877年及1983年前后发生了降水突变。空间相关分析表明,重建的上年7月至当年6月降水量对额尔齐斯河上游阿勒泰地区的降水量具有很好的空间代表性。此外,重建结果还与周边地区其他基于树轮资料重建的降水序列的干湿变化有较好的一致性。

A 291 year precipitation reconstruction in the Upper Irtysh river basin based on tree-ring width

Dendroclimatology is one of the most important methods for reconstructing past climate change. Owing to the characteristics of precise dating, annual resolution, and comparability with meteorological observational data, tree-ring data have been widely used as important archival material in paleoclimatic research. We selected Siberian spruce (Picea obovata Ledeb) trees with little or no apparent evidence of human or other disturbances for sampling. Tree-ring chronologies at six individual sites were developed for Siberian spruce from the Upper Irtysh River, and then a regional tree-ring chronology (RTC) was established based on all of the detrended data obtained from individual tree cores of the six sites. We analyzed the correlations between the RTC chronology and the meteorological data of the Fuyun weather station. The results showed that precipitation was the main factor limiting the radial growth of spruce trees in this region. The RTC chronology showed the highest correlation with precipitation from the previous July to June of the current year. Based on the results of correlation analysis, we reconstructed annual precipitation patterns (July-June) of the Upper Irtysh River basin from 1722 to 2012. The precipitation reconstruction explained 55.1% of the instrumental precipitation variance during the period of 1963-2012. During the past 291 years, there were nine wet periods and eight dry periods. The wettest period occurred from 1984 to 2008, and the driest period occurred from 1877 to 1891. The period 1829-1876 was the most extended wet period, while the period 1807-1828 was the most prolonged dry period. Power spectrum analysis indicated the existence of some decadal (21.6 and 24.3 year) and interannual (2.1, 2.3 and 3.2 year) cycles. A moving t-test indicated that an abrupt change of precipitation occurred in 1876-1877 and 1983 in this region. The results of spatial correlation analysis indicated that our precipitation reconstruction correlated well (r>0.6) with the July-June precipitation gridded data over a large area of the Altay region, with the highest correlations occurring in the Southern Altay Mountains. When compared with other tree ring based precipitation reconstructions from the surrounding area, our results showed a similar trend in the variation of drought and precipitation.