基于树轮重建的宁夏河东沙地西部公元1899年来年降水量的变化

Annual precipitation variation reconstructed by tree-ring width since A.D. 1899 in the west part of Hedong sandy area of Ningxia

在分析我国季风区西北缘宁夏河东沙地西部的油松（Pinus tabulaeformis）树木年轮宽度年表与气温降水相关关系基础上,建立了树轮宽度指数与年降水量的转换方程。交叉检验结果表明转换方程比较稳定,重建结果合理可靠。公元1899年来降水量重建结果表明：研究区在20世纪40年代以前,降水变化波动幅度较大,年际间干湿变化明显,20世纪40-80年代间降水波动幅度变小且频率增加,20世纪80年代以后降水变化波动幅度又趋于增大且频率减小;与昌灵山、贺兰山和祁连山东段降水变化对比分析发现河东沙地西部的降水量变化与周边地区气候演变存在一定的同步性;宁夏河东沙地西部20世纪10年代、20世纪20-30年代初期、20世纪末以及2004-2006年的相对干旱时期有利于该区沙漠化范围的扩大,对该区沙漠化治理不利,而20世纪初期、20世纪10年代末期、20世纪30-40年代、20世纪90年代的相对湿润时期在一定程度上减缓了暖干化趋势,有利于沙漠化范围的缩小。周期分析结果表明,宁夏河东沙地西部1899年来降水量变化存在2~4 a、5~7 a和10 a左右变化周期。

Based on the analysis of relationship between tree ring width of Pinus tabulaeformis in Luoshan Mountains of the west part of Hedong sandy area of Ningxia and climate factors,we developed the reconstructed equation of annual precipitation since A.D.1899,and the calibration equation is stable and the reconstructed results are reliable according to the cross verification.The reconstructed annual precipitation shows the characteristics of remarkable fluctuation before 1940s,ordinary ambit and high frequent change during 1940s-1980s and high periodic extent and low frequent change after 1980s;We find that there are some coincidences with the climate change taken place in Changling Mountains,Helan Mountains and the east part of Qilian Mountains;The relatively dry periods in early of 20th century,1920s-1930s,the end of 20th century and 2004-2006 happened in the west part of Hedong sandy area of Ningxia are benefinical to desertification and unfavorable to desertification prevention and control,while the relatively humid period in 1910s-1920s,1930s-1940s and 1990s is favorable to desertification prevention and control,and the weakening of warming and drying;The periods of annual precipitation in the west part of Hedong sandy area of Ningxia since A.D.1899 are mainly 2-4 years,5-7 years and 10 years or so.