| 摘要: |
| 由于热带地区大部分树木缺乏清晰的年轮，因此树木年轮的研究相对较为薄弱。树轮稳定同位素较树轮宽度能更好地记录环境变化的信息，特别是研究年内稳定同位素可以提供气候变化的季节动态信息。本研究以西双版纳地区的思茅松（Pinus kesiya Royle ex Gordon）为研究材料，建立了1985—2018年的思茅松年轮宽度、早材和晚材稳定氧同位素（ δ18OEW和 δ18OLW）年表，分析了树轮宽度、 δ18OEW和 δ18OLW年表与温度、降水和标准化降水蒸散指数（SPEI）等气候要素的相关关系，并研究了思茅松 δ18OEW和 δ18OLW记录的降水、SPEI变化以及与大尺度季风环流的关系。结果表明：西双版纳地区思茅松树轮 δ18OEW和 δ18OLW的均值接近，并且均呈下降趋势，这种下降趋势可能与西双版纳地区的雾日减少有关。树轮宽度对气候因子响应不敏感，仅与上一年7月的温度呈显著负相关关系，与上一年7月降水呈显著正相关关系。 δ18OEW主要记录了生长季早期（4月和5月）的降水和SPEI信号，而 δ18OLW主要记录了生长季末期（8月）的降水和SPEI信号。 δ18OEW和 δ18OLW分别能很好地代表区域5月和8月的干湿变化。树轮 δ18O也受到了ENSO的影响，其中树轮 δ18OEW与3—12月厄尔尼诺呈显著正相关关系，树轮 δ18OLW与9—12月厄尔尼诺呈显著正相关关系（p＜0.05）。该研究表明西双版纳地区的思茅松树轮早晚材 δ18O具有重建区域干湿变化的潜力。 |
| 关键词: 亚洲热带 稳定氧同位素 早材和晚材 气候响应 空间相关 |
| DOI：10.7515/JEE202002 |
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| 基金项目:国家自然科学基金项目（31870591，31770533）；中国科学院东南亚中心项目（Y4ZK111B01）；中国科学院
版纳植物园“135项目”突破一项目（2017XTBG-T01） |
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| Climate responses of tree-ring widths and stable oxygen isotopes of Pinus kesiya in Xishuangbanna, southwestern China |
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NIU Ying, YANG Raoqiong, FU Peili, ZHAO Fan, FAN Zexin
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1. Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Xishuangbanna 666303, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. Ailaoshan Station of Subtropical Forest Ecosystem Studies, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Jingdong Yunnan, China
4. Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Xishuangbanna 666303, China
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| Abstract: |
| Background, aim, and scope Due to the lack of clear ring boundaries in most tropical tree species, tree ring studies in tropical region are still rare. Tree ring stable isotopes variations generally record stronger climatic signals compared with ring width, thus have great potential in dendroclimatical study in tropical region. Moreover, intra-annual variations of tree ring stable isotopes could provide seasonal climatic information. The present study aims to investigate the potential of tree ring width and stable oxygen isotope variations of a tropical pine species in Xishuangbanna, southwestern China. Materials and Methods The present study developed tree ring-width and stable oxygen isotope chronologies in earlywood ( δ18OEW) and latewood ( δ18OLW) of Pinus kesiya Royle ex Gordon (Simao pine) in Xishuangbanna. We performed correlation analyses between tree ring width, δ18OEW and δ18OLW and climatic factors such as monthly mean temperature, monthly precipitation and Standardized Precipitation Evapotranspiration Index (SPEI) during the period 1985—2018. Spatial representatives were investigated by correlating δ18OEW and δ18OLW with regional precipitation. The relationships between tree ring oxygen isotope and El Niño-Southern Oscillation (ENSO) were also investigated. Results The mean values of δ18OEW and δ18OLW were 23.08‰ and 23.83‰, respectively, and both δ18OEW and δ18OLW showed decreasing trends. Tree ring-width chronology of P. kesiya in Xishuangbanna correlated negatively with the temperature and positively with precipitation in July of the previous year. δ18OEW chronology were negatively correlated with precipitation in the early growing season (May), whereas δ18OLW mainly recorded precipitation signal at the end of the growing season (August). δ18OEW was positively correlated with SPEI in April, and negatively correlated with SPEI in May, whereas δ18OLW was negatively correlated with SPEI in August. Both δ18OEW and δ18OLW were positively correlated with El Niño and negatively correlated with Southern Oscillation Index. Discussion Our study showed that tree growth of P. kesiya in Xishuangbanna is not sensitive to climate variables. The mean value of δ18OEW (23.08‰) and δ18OLW (23.83‰) is similar, which may due to the low variability of rainfall δ18O during the growing season. The decreasing trends of both δ18OEW and δ18OLW could be related to the decreasing of the contribution of fog water to the tree water use in Xishuangbanna. δ18OEW and δ18OLW were negatively correlated with regional precipitation in May and August, respectively. Strong correlation between tree-ring δ18O and regional precipitation confirmed that tree ring δ18O has the potential to reconstruct regional precipitation variability in the tropical regions. Moreover, tree ring δ18O showed high correlation with ENSO index, which implies that ENSO has an important influence on the hydro-climate in the study region. Conclusions Tree ring δ18OEW mainly records precipitation signal in May of the early growing season, while δ18OLW mainly records precipitation signal in August at the end of the growing season (latewood formation period). The δ18OEW and δ18OLW can represent the regional precipitation patterns in May and August, respectively. Tree-ring was δ18O mainly positively correlated with El Niño and negative correlation with the Southern Oscillation Index. Recommendations and Perspectives This study indicates that earlywood and latewood δ18O of P. kesiya in this region have high potential to reconstruct hydro-climate history in different seasons. |
| Key words: Asian tropics stable oxygen isotope earlywood and latewood climate response spatial correlation |
