新疆夏尔希里1850—1870年森林生长压抑事件及启示

Suppression of forest growth in 1850 - 1870 and its implications in Xiaerxili, Xinjiang

摘要:

全球气候变暖增加了极端干旱事件发生的频率和强度,而极端干旱事件的发生和影响在时间和空间上表现不同,扩展时空尺度上极端干旱事件的信息有助于认识其发生特征并准确评估其影响。本研究在我国最年轻的国土之一,新疆夏尔希里,采集了雪岭云杉(Picea schrenkiana Fisch.et Mey)树木年轮样本,建立了近300年的树轮宽度序列,分析了树木径向生长与气候因素的关系,探讨了历史极端气候事件及其影响。结果显示：1)树木径向生长与4月的饱和水汽压差(VPD)显著负相关,且在近期明显增强；2)重大森林生长压抑事件出现在1850—1870年,其间树木径向生长速率为过去300年最低；3)在1850-1870年间森林生长压抑事件后期,有些树木表现出生长释放现象。这些结果表明：夏尔希里地区在1850年代很可能发生了以大气干旱为主要特征的超级持续干旱事件,并导致之后森林生长的干旱“遗留效应”和部分树木的死亡。随着区域VPD升高趋势的持续,夏尔希里自然保护区面临极端干旱事件的风险也将升高,雪岭云杉林再次发生生长压抑事件甚至大面积死亡的风险将进一步增大。建议加强对该区域森林生长的实时监测,准确评估森林生长的健康风险,制定防旱防灾的相应措施。

Abstract:

Global warming increases the frequency and intensity of extreme drought events, and the occurrence and impact of extreme drought events are different in time and space. Expanding the information of extreme drought events on spatio-temporal scale is helpful to understand their occurrence characteristics and accurately assess their impact. In this study, tree-ring samples of Picea schrenkiana Fisch.et Mey were collected in Xiaerxili, Xinjiang, one of the youngest regions in China. The tree-ring width chronology was established, the relationship between radial growth and climate factors was analyzed, the historical extreme climate events and their effects also were discussed. The results showed as follows: 1) There was a significant negative correlation between radial growth and vapor pressure deficit (VPD) in April, and it was significantly enhanced recently; 2) A major forest growth depression occurred in 1850-1870, during which the radial growth rate of trees was the lowest over the past 300 years, and another forest growth depression occurred in 1917-1919; 3) In the late period of forest growth suppression event from 1850 to 1870, some trees showed growth release phenomenon. These results indicate that the Xiaerxili experienced a super persistent drought event in the 1850s and 1860s, characterized primarily by atmospheric drought, which resulted in drought "legacy effects" on forest growth and the death of some trees. With the increasing trend of regional VPD, the risk of extreme drought events in Xiaerxili will also increase, and the risk of growth suppression events and even large-scale death of Picea schrenkiana will further increase. It is suggested to strengthen the real-time monitoring of forest growth in this region, accurately assess the health risks of forest growth, and formulate corresponding measures for drought and disaster prevention.