树轮稳定碳同位素研究进展

Review of tree-ring stable carbon isotopes

近年来,树轮稳定碳(C)同位素的实验、分析方法渐趋成熟,被广泛应用于树轮气候学、树木生理学和森林生态学等领域。本文基于文献统计的方法回顾了树轮稳定C同位素的发展历程,并对未来研究动向进行展望。结果发现:1)基于树轮稳定C同位素的研究主要分布在北半球中纬度地区,多集中于气候学和生理学领域,生态学方面的研究较少;2)树轮稳定C同位素能够重建过去百年至千年的温度、降水、相对湿度、云量等气候要素的变化;3)树轮稳定C同位素能够指示树木内在水分利用效率,用于研究树木应对气候或环境事件(如干旱、大气污染等)的生理响应;4)树轮稳定C同位素数据还能够提高动态植被模型、树木生长过程模型模拟的精度,进而反演及预测气候和环境变化。综上,树轮稳定C同位素从用于重建气候因子变化,发展为探究树木响应气候环境的生理过程,并通过嵌入动态植被模型和地球系统模型进行模拟和预测。未来仍需加强对光合作用后稳定C同位素分馏机制的研究,挖掘树轮稳定C同位素在重建古气候的潜力,并结合树木生长过程模型、动态植被模型等模拟并预测气候和环境变化。

In recent years,the development of experimental and analytical methods has greatly increased the number of publications related to tree-ring stable carbon(C)isotopes.Based on the bibliometric method,we summarized related studies and categorized them into three major themes:'climatology','physiology',and'ecology'.The results showed that:studies on tree-ring stable C isotopes were clustered in the mid-latitude Northern Hemisphere,with fewer sites in low and high latitudes and the Southern Hemisphere.The published works were mainly focused on climatology and physiology while there was fewer research in the field of ecology.The analysis of climate sensitivity of indicated that tree-ring stable C isotopes correlate positively to temperatures in 88.46%of the total sampling sites and that C isotopes from about 81.25%sites respond negatively to humidity.The responses were more consistent in high-latitude regions which were mainly related to summer,while climate responses are more variable in middle and low latitudes.A detailed synthesis of relevant publications in the most recent decade showed that there is an increasing implication in the field of physiology.Tree-ring stable C isotopes can reflect the intrinsic water-use efficiency of trees and have been used to study the physiological response of trees to climatic and non-climatic disturbances,such as drought,fire,and atmospheric pollution.Stable C isotope data of tree rings have also been used to assess forest productivity and to enhance the accuracy of dynamic vegetation and physiological models.Future studies are needed to better understand the fractionation mechanism of stable C isotopes after photosynthesis,explore the potential of tree-ring stable C isotopes for reconstructing paleoclimate and environment,and reveal the significance of intra-annual variations of tree-ring stable C isotope ratios(δ^(13)C).Moreover,tree-ring stable C isotopes can be combined with physiological process models or dynamic vegetation models to predict future climate and environment changes.