树轮记录的黄河源区过去390 a流量变化

论文利用采自黄河源区的两个样点的祁连圆柏树轮样本建立了区域树轮宽度年表,分析了树木生长与流量的关系,结果表明1—7月的平均流量与树轮宽度密切相关,相关系数达0.73。由此重建了黄河源区过去390 a来的流量变化,统计检验结果表明,重建方程方差解释量高达53.6%。重建序列大体经历了7个丰水期和10个枯水期。周期分析结果表明,重建序列存在着42、18和2~4 a左右的显著变化周期。区域对比结果表明,重建结果与周边其他基于树轮资料的重建序列的干湿变化有较好的一致性,证明了论文重建序列的准确性。

Streamflow Reconstruction Based on Tree Ring in the Source Region of Yellow River Region over the Past 390 Years

The source region of the Yellow River in the hinterlands of the Tibetan Plateau is the principal headstream of the Yellow River. The ecological environment has deteriorated in recent decades and climate change influences have been observed in the area. Changes in the ecological environment mainly include substantial streamflow reduction, wetland destruction and severe droughts. Therefore, research regarding water resources including river formation and evolution in this area is needed for the preservation of the ecological environment and water supply. It is important to develop new tree-ring chronologies in the source region of the Yellow River in order to recognize streamflow variation in the past. A regional tree-ring width chronology (RC) was developed based on Sabina przewalskii Kom samples at two individual sites in the source region of the Yellow River. Tree-ring samples were prepared, cross-dated and measured following conventional procedures. Statistical analysis showed that the regional tree-ring chronology (RC) was highly correlated (r=0.73) with instrumental streamflow records from January to July at the hydrological stations. Based on the analyses, we reconstructed streamflow records from January to July during 1624-2013. The reconstruction captured 53.6% of the instrumental streamflow variance. In the past 390 years, we identified seven relatively high streamflow periods (1632-1643, 1657-1695, 1751-1764, 1798-1813, 1836-1856, 1886-1914 and 1934-1947) and ten relatively low streamflow periods (1644-1656, 1696-1706, 1708-1720, 1727-1750, 1787-1797, 1814-1835, 1857-1885, 1915-1933, 1952-1968 and 1993-2006). The longest high period is 1657-1695 (39 years), and the longest low period is 1857-1885 (29 years). The MTM analysis suggested the existence of significant change circles with intervals of 42, 18 and 2-4 years. The reconstruction was validated by comparison it with other reconstructions in the surrounding area. The streamflow reconstruction significantly correlates with the constructions in Tongtian River (r=0.51, P<0.001) and the upper Yellow River (r=0.60, P<0.001). Also, the streamflow reconstruction significantly correlates with the precipitation reconstructions in Delingha region (r=0.55, P<0.001) and the southern Tibetan Plateau (r=0.46, P<0.001). These three areas shared the same drought periods (1650s-1670s, 1780s-1800s, 1820s-1830s, and 1920s-1930s) and wet periods (1840s-1850s, and 1880s-1910s). The consistency and correlation of constructions in these regions proved the accuracy of the reconstruction sequence in this article.