A 645 -Year Precipitation Reconstruction in Baluntai Region on Southern Slope of Mid-Tianshan Mountains Based on Tree-ring Width
Dendroclimatology is one of the important methods for examining the past global climate changes and the tree-ring data were used widely as an important archive in paleoclimatic research because of its precise dating, annual resolution, and high correlation with instrumental meteorological data. Based on tree-ring chronologies, long-timescale climate variations have been reconstructed on both regional and hemispheric spatial scales.The study area, the Baluntai region is located on the southern slope of the mid-Tianshan Mountains in Xinjiang.So far there are a few dendroclimatogical studies being carried out in this region. The studies were focused on the analysis of tree-ring chronologies' statistics and correlation of chronologies with meteorological data, but the reconstruction of climatic variations has not been done. Because of this, it is very important to reconstruct the climatic variation series in this region in order to recognize the climatic variations on the southern slope of the midTianshan Mountains in the past. In the summer of 2005, 66 spruce (Picea schrenkiana) tree-ring samples were collected from Fustan Gully (FST) (42°45′15.9″N, 86°27′40.0″E), which is located in a mountainous area of Baluntai region. Selected trees did not have outward signs of disturbance ( e. g. , abrasion scarring, cut branches). Tree-ring samples were prepared, cross-dated and measured following conventional procedures. The site (FST) of tree-ring width residual chronologies was chosen in this study. In addition, meteorological data of Baluntai station close to sampling site were used. The calculation shows that the tree-ring width residual chronology ( RESt+1 ) is significanfiy correlated with the precipitation from the current July to next June (r =0.73, p ＜0.01,N=44). In this paper, tree-ring width residual chronology (RESt+1) has been used to reconstruct the precipitation (from the current July to next June) of this region since 1360 A. D. and the explained variance of the function was 52％ (F =48.12, p ＜0.01 ). After 21-years mean of reconstructed precipitation series was calculated,twelve dry periods in the past 645 years were found in (1370？) - 1396, 1442-1469, 1501-1539, 1565-1586, 1619-1652, 1679-1688, 1707-1728, 1755-1788, 1811-1836, 1863-1886, 1907-1918 and 1940-1987, and twelve wet periods were found in 1397-1441, 1470-1500, 1540-1564, 1587-1618,1653-1678, 1689-1706, 1729-1754, 1789-1810, 1837-1862, 1887-1906, 1919-1939 and 1988-(1994？), respectively. Power spectrum analysis shows that there exist the 16.5-17.2 a, 10.7-11 a, 6.7 a,2.4-6.6 a and 2.1 a quasi-cycles in precipitation. The periods of 10.7 a to 11 a respond to sunspot cycle length (SCL) and the cycle of aridity in Northwest China. The periods of 2.4 a to 6.7 a probably are related to ENSO events, and the cycle of 2.1 years probably is related to the quasi-biennial oscillation (QBO). Moving t-test technique (MTT) shows that the abrupt change of precipitation occurred in 1496 in this region.
NETL
NSTL
万方数据
维普
