Department of Science and High Technology, Università degli Studi dell'Insubria, Via Valleggio, 12, 22100 Como, Italy.
Department of Biotechnology and Life Sciences, Università degli Studi dell'Insubria, Via Jean Henry Dunant, 3, 21100 Varese, Italy.
Sci Total Environ. 2021 Mar 1;758:143672. doi: 10.1016/j.scitotenv.2020.143672. Epub 2020 Nov 21.
The chemical analysis of tree rings has attracted the interest of researchers in the past five decades in view of the possibility of exploiting this biological indicator as a widely available, high-resolution environmental archive. Information regarding the surrounding environment can be derived either by directly measuring environmental variables (nutrient availability, presence of pollutants, etc.) or by exploiting proxies (e.g. paleoclimatic and paleoenvironmental reconstructions). This review systematically covers the topic and provides a critical view on the reliability of dendrochemical information. First, we introduce the determinable chemical species, such as major elements, trace metals, isotopic ratios, and organic compounds, together with a brief description of their uptake mechanisms and functions in trees. Subsequently, we present the possibilities offered by analytical techniques in the field of tree ring analysis, focusing on direct methods and recent developments. The latter strongly improved the details of the accessible information, enabling the investigation of complex phenomena associated with plant life and encouraging the direct analysis of new analytes, particularly minor organic compounds. With regard to their applications, dendrochemical proxies have been used to trace several processes, such as environmental contamination, paleoclimate reconstruction, global environmental changes, tree physiology, extreme events, ecological trends, and dendroprovenance. Several case studies are discussed for each proposed application, with special emphasis on the reliability of tracing each process. Starting from the reviewed literature data, the second part of the paper is devoted to the critical assessment of the reliability of tree ring proxies. We provide an overview of the current knowledge, discuss the limitations of the inferences that may be drawn from the dendrochemical data, and provide recommendations for the best practices to be used for their validation. Finally, we present the future perspectives related to the advancements in analytical instrumentation and further extension of application fields.
过去五十年，人们对树木年轮的化学分析产生了兴趣，因为这种生物指标有可能被开发为广泛可用的高分辨率环境档案。可以通过直接测量环境变量（养分供应、污染物存在等）或利用示踪剂（例如古气候和古环境重建）来获取有关周围环境的信息。本综述系统地涵盖了这一主题，并对树木年轮化学信息的可靠性进行了批判性评价。首先，我们介绍了可测定的化学物质，如主要元素、痕量金属、同位素比和有机化合物，以及它们在树木中的吸收机制和功能的简要描述。随后，我们介绍了树木年轮分析领域分析技术提供的可能性，重点介绍了直接方法和最新发展。后者大大提高了可获取信息的详细程度，使与植物生命相关的复杂现象的研究成为可能，并鼓励对新分析物（特别是痕量有机化合物）进行直接分析。关于它们的应用，树木年轮化学示踪剂已被用于追踪多种过程，如环境污染、古气候重建、全球环境变化、树木生理学、极端事件、生态趋势和树木起源。每个提出的应用都讨论了几个案例研究，特别强调了追踪每个过程的可靠性。从综述的文献数据出发，本文的第二部分致力于对树木年轮示踪剂可靠性的批判性评估。我们提供了当前知识的概述，讨论了从树木年轮化学数据中得出的推论的局限性，并为其验证提供了最佳实践建议。最后，我们提出了与分析仪器的进步和进一步扩展应用领域相关的未来展望。
