青海沙利克山祁连圆柏千年树轮宽度序列的变化特征

Characteristics of millennial tree-ring width variations of Qilian juniper in Shalike Mountain, Qinghai

利用功率谱、奇异谱和小波分析等方法对在青海沙利克山建立的两条祁连圆柏 (Sabi naprzewalskiiKom )千年树轮宽度序列进行了变化特征的分析 ,发现在低频变化上都存在2 0 0年的最显著周期和百年左右的显著周期 ;各种周期存在不同的演变特征 ,2 0 0年周期在15～ 17世纪最为盛行 ,百年左右的周期变化自 18世纪初以来较为突出。 15世纪下半叶是轮宽序列千年来最突出的低值期 ,它主要体现了 2 0 0年周期的变化 ,而 2 0世纪后期的高值区则主要是百年左右周期变化的作用。轮宽序列的低频变化与太阳活动的长期变化之间存在较好的对应关系 ,说明祁连圆柏年轮宽度序列所指示的气候低频变化可能受太阳活动的影响。

Qilian juniper ( Sabina przewalskii Kom ) growing in the mountainous area of the easterm part of Qaidam Basin is sensitive to climate change It can reach one millennial years old and the tree ring width chronology can be used to reconstruct climate change over the past 1000 years Power spectrum analysis, Singular Spectrum Analysis (SSA) and wavelet analysis were utilized to trace the variations recorded in two standard tree ring width chronologies (WL3 and WL4) of Qilian juniper in Shalike Mountain, Qinghai, China The power spectrum of the series showed low frequency periodicity of 200 years are most statistically significant at the 95% confidence level for both chronologies Analysis of the power spectrum of both series also showed evidently that low frequency variations of century scale are present in the chronologies It was found that the most important cycle was 200 years for both chronologies by SSA, cycle of 133 years for WL3 and 100 years for WL4 are also identified by this method The reconstructed components of paired eigenvectors of SSA showed that different scale cycles had different behaviors over the past 1000 years Wavelet analysis can provide information on the amplitude of periodic signals and their variations with time The Morlet wavelet coefficient distributions indicated that the 200 years cycle was most prevailing from the 15th to the 17th century for both chronologies, the century scale cycles were pronounced since the 18th century The prominent low value of the ring width in the second half of 15th century is affected by the cycle of 200 years, the high value in the late 20th century is the contribution of century scale periodicities One possible explanation of the low frequencies in the ring width data might be related to the fluctuations of the solar activity Narrow ring width seems to occur during quiet solar periods such as the Wolf, Sprer, Maunder and Dalton solar minima, suggesting that the low variation of the climate indicated by tree ring width may be affected by the long term change in solar activity