| 摘要: |
| 利用采自吕梁山北部地区的油松样本，建立了过去175年来的树轮宽度年表。相关分析表明：标准年表（STD）与当年5—6月的帕尔默干旱指数（Palmer drought severity index，PDSI）相关性最好，相关系数为0.687（n=50，p＜0.001）。因此，采用树轮宽度标准年表（STD）序列重建了1829—2003年5—6月的PDSI序列，重建方程的方差解释量达到47.16%。重建序列发现9个偏湿时段，分别为1833—1836年、1845—1851年、1857—1863年、1869—1874年、1882—1887年、1896—1899年、1932—1939年、1949—1965年、1975—1985年；10个偏干时段，分别为1829—1832年、1837—1844年、1852—1856年、1864—1868年、1875—1881年、1888—1895年、1900—1931年、1940—1948年、1966—1974年、1986—2003年。同时发现20世纪20年代的严重干旱事件以及20世纪末气候干旱化加重的趋势。空间相关结果显示：重建的PDSI代表了周边大范围的干旱变化，同时，与基于历史文献的干湿指数（DWI）显著相关（p＜0.002），说明无论是空间还是时间尺度上，重建结果都可以代表吕梁山周边大范围的干旱变化。此外，重建序列与不同定义的东亚夏季风指数都显著相关（p＜0.02），说明东亚夏季风对研究区的干湿变化具有调制作用。多窗谱分析表明重建序列存在2—7年、12年、13.6年、19.2年、21.6年、26.1年的周期变化，这些周期变化可能与ENSO、太阳活动有关。 |
| 关键词: 吕梁山北部 树轮宽度 PDSI重建 东亚季风 |
| DOI：10.7515/JEE192024 |
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| 基金项目:国家自然科学基金项目（41873021）；中国科学院青年创新促进会（2017451）；中国科学院“西部之光”项目；陕西省青年科技新星项目 |
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| PDSI variations recorded by tree rings in the northern Lüliang Mountains during the past 175 years |
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WANG Zhenwei, LI Qiang, LIU Yu, YANG Yinke, REN Meng, CUI Linlin
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1. Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region, School of Environmental Science and Engineering, Chang’an University, Xi’an 710054, China
2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
3. CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
4. Joint Center for Global Change Studies (JCGCS), Beijing 100875, China
5. Department of Environmental Science and Technology, School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China
6. University of Chinese Academy of Sciences, Beijing 100049, China
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| Abstract: |
| Background, aim, and scope Lüliang Mountains, range in the west of Shanxi Province, China. Northeast striking, about 400 kilometers from north to south, located between the Yellow River and the Fenhe River. Due to the decrease of available water in recent years and the aggravation of drought, it is necessary to study the drought history of this area. In this paper, tree rings of pines from Lüliang Mountains were used to study the dry-wet change in the past and its influencing factors. Materials and methods 42 pine cores were collected from Lüliang Mountains, then they were dried, fixed and polished in the laboratory, the width was measured by LINTAB with an accuracy of 0.01 mm. The COFECHA program was then used for cross-dating quality control to ensure that each tree-ring had an accurate calendar year. Finally, three chronologies were generated with ARSTAN. Results Correlation analysis showed that the palmer drought index (PDSI) had the best correlation with the standard chronology (STD) from May to June, with a correlation coefficient 0.687 (n=50, p＜0.001). In addition, the STD chronology retained more low-frequency signals than the RES chronology. So the width standard chronology (STD) were selected to reconstruct the PDSI index changes from May to June during 1829—2003, the variance interpretation of the reconstructed equation was 47.16%. The reconstructed sequences including 9 wet sequences and 10 dry sequences. Discussion The reconstruction sequence reveals the drought in the 20th century and the intensification of drought in the end of the 20th century. Compared with the DWI index sequence in Yang et al (2013), the correlation coefficient is −0.235 (n=175, p＜0.002). After 10 years of low-pass filtering, the correlation coefficient is −0.4, indicating that the reconstruction sequence is reliable. Conclusions The east Asian summer monsoon has an important influence on the dry and wet changes in the study area. Multiwindow spectral analysis showed that the reconstructed sequences had periodic changes of 2—7 a, 12 a, 13.6 a, 19.2 a, 21.6 a and 26.1 a, which may be related to ENSO and solar activity. Recommendations and perspectives Further research into the factors affecting drought in the region is needed. At the same time, finding other sources of water available to alleviate water shortages is essential. |
| Key words: northern Lüliang Mountains tree ring width PDSI reconstruction the east Asian monsoon |
