新疆罗布泊地区近160年来红柳沙包沉积纹层δ^13C与气候重建

THE δ^(13)C SEQUENCE OF Tamarix CONE SEDIMENTARY VEINS AND CLIMATE RECONSTRUCTION DURING LAST 160 YEARS IN LOP NUR REGION, XINJIANG, CHINA

红柳沙包具有准确的计年和很强的环境信息储存功能,可以用来恢复数百年来的气候和环境变化。研究发现,罗布泊红柳沙包沉积纹层红柳落叶δ^(13)C序列高频变化受多个气候要素的综合影响,重建的罗布泊地区1839年以来的年平均气温、8～10月空气平均相对湿度及4～5月平均风速,较好地反映了该地区168年来的气候变化。对红柳落叶δ^(13)C高频变化序列的功率谱分析发现,δ^(13)C序列含有显著的42.0a,10.5a,8.4a,4.0a,3.7a和2.9a等准变化周期,其中,准10.5a周期与太阳黑子约11.0a的活动周期基本一致。

Tamarix cone is one kind of vegetation cones formed by shrubs with Tamarix and other plant species,many of which exist in the region in and around Taklimakan Desert. Most Tamarix cones range in height from 3m to 15m and in length from 5m to 50m（long axis）. It is also discovered by investigation that in the region of Lop Nur there are many Tamarix cones with clear layers composed of sand and dead trigs and leaves of Tamarix. Those have the functions of exact dating and strong environmental information storage, by which the change of climate and environment could be reconstructed for recent hundreds of years. At the site of 39.58°N,89.78°E, we take 168 samples in a top part of Tamarix cone from the top layer to the low according to every layers. The age continuity of sedimentary veins is determined by 210Pbex of sand materials in sedimentary veins,the sample age is from 1839 to 2006. The Tamarix twigs and leaves are used in carbon isotope test. Research results show that the high-frequency change of δ^13C sequence in Tamarix cone sedimentary veins in Lop Nur region is impacted by some climate elements jointly. The reconstructed climate elements such as mean relative humidity from Aug. to Oct., wind speed from Apr. to May, and the mean annual temperature since 1839 reflect preferably the historical.climate variation during the past 168 years in Lop Nur region. The warmer climate periods include 1849 - 1865A. D., 1891 - 1936A. D., 1987 - 2006A. D., the cooler ones include 1839 -1848A. D., 1866 - 1890A. D., 1937 - 1986A. D. The relative air humidity shows the slow upward trend before 1930A. D.,since early 20＇s century it was high, later it began to decline, during the time from the 30＇s to the late 60＇s of 20th century it has decreased obviously, and since the 70＇s of 20th century it has been increasing gradually. The climate change has the features of alternative change between the cool-dry and the warm-humid patterns. Analysis of power spectrum indicates that the quasi-periodic oscillations of 42. 0a, 10. 5a, 8.4a,4. 0a, 3.4a and 2. 9a are involved in the high-frequency information series. The quasi-periodic of 10. 5a reflects the active cycle of sunspot around 11.0 years.