Tree-ring Based Climate Reconstruction For Qilian Mountain

Qilian Mountain is located in the area influenced both by monsoon and westerlies. And it is the climate change sensitive area and the ecology frail belt. It is important that understanding the climate change history of this area to analyze the Hexi area current ecological environment change and utilize future water resources.We analyze the precipitation and temperature of annual, growing season C4C9 (Current April to September) and non-growing season P10C3 (Previous October to Current March) with rotated experience orthogonal function (REOF). The study area was divided into four climatic zones according to the high load values and the trend of the main components.We collected tree-ring samples for 8 sites in Central and Eastern Qilian Mountain and pretreated samples with the standard laboratory experiment methods. Above the normative detrending methods, the "signal-free" method was applied in detrending, so the climate information recored by tree-ring was more accurate. Then,8 standardized (STD) tree-ring chronologies were established.Tree-growth variability and climate-growth associations were investigated in different climatic zones by means of response function and correlation analyses. There were a lot differences between different climatic zones, moreover there were some difference between different species in the same climatic zone. Tree-ring width chronologies of Sabina Przewalskii in climatic zone I positive responsed to the growth of previous year and summer temperature. Tree-ring width chronologies of S. przewalskii in climatic zone II positive responsed to winter temperature of previous year and precipitation of growth season, and chronology of Pinus tabulaeformis in the same zone positive responsed to precipitation of previous and current growth seasons. Chronologies of Sabina Przewalskii from zone III positive responsed to precipitation of growth season.According to the high correlation between tree-ring chronologies and climate, climate change was reconstruction in different climatic zones. We reconstructed C6C9 temperature in zoneâ…¡, and reconstructed P8C6 precipitation in zoneâ…¡, reconstructed P8C7 precipitation in zoneâ…¢. Through spectral analyses,2-3 yr cyclic was shown in all climatic zones, which means the whole study area climate was influenced by the same factor.We compared temperature reconstruction in zoneâ… with published temperature reconstruction in Qilian Mountain, temperature of Lanzhou weather station, and all of them has the same tend of increasing. We Campared precipitation reconstructions of zoneâ…¡andâ…¢with published work HYG in zoneâ…¢, WQL in zoneâ…£, Qinghai DLH1, XLM, and HLM. The precipitation reconstructions in zoneâ…¢had the same trend both in low and high frequency. The precipitation in zoneâ…¢was in the same trend with precipitation in zoneâ…£except in 1870s and 1950s. The precipitation in zoneâ…¡was different from the others, and it had the same trend with XLM and HLM before 1940s and had the same trend with the chronologies from Central and Western Qilian Mountain and Qinghai Delingha region. So we supposed that Eastern Qilian Mountain were probably controlled by different climate styles during the period before 1940s and the period after 1940s, and which might be in relation with monsoon weaken.