Purpose of Review

We conducted a literature survey and meta-analysis to assess, in Mediterranean forests impacted by drought, the role of xylem functional traits as indicators of tree health, and their potential to adjust over a range of climatic conditions to support tree performance and survival. We aimed also to depict the geographic variability of xylem functional traits among Mediterranean forest trees as a tool for regional scale-oriented vulnerability assessment.

Recent Findings

Associations were investigated among xylem functional traits, hydraulic safety, and whole plant drought resistance for tree species in Mediterranean-type climates. Variable data were available from a number of study cases of Mediterranean forest communities impacted by intense drought, wherein tree growth and xylem functional traits were investigated along with tree decline and dieback episodes. Variable data were available from a number of studies that analyzed xylem trait adjustments to climatic conditions at different temporal scales.

Summary

We observed differing growth patterns and xylem conduit area responses in healthy and unhealthy trees and we sketched hydraulic strategies that may fit observed patterns. Overall, a clear role of xylem conduit size as stand-alone tree health indicator did not emerge. We showed that xylem traits may adjust along different temporal scales and may support the performance and health of Mediterranean tree species over a range of climatic conditions. We outlined substantial geographic variability in xylem traits across the Mediterranean region, suggesting patchy responses to increasing drought. Knowledge gaps and needed lines of research are highlighted.

中文翻译：

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木质部功能性状作为地中海森林健康指标

审查目的

我们进行了文献调查和荟萃分析，以评估在干旱影响下的地中海森林中，木质部功能性状作为树木健康指标的作用，以及它们在一系列气候条件下进行调整以支持树木性能和生存的潜力。我们的目的还在于描绘地中海林木中木质部功能性状的地理变异性，以此作为面向区域尺度的脆弱性评估的工具。

最近的发现

研究了地中海型气候中树种的木质部功能性状，水力安全性和全株抗旱性之间的联系。可以从许多受到强烈干旱影响的地中海森林群落的研究案例中获得可变数据，其中对树木生长和木质部功能性状以及树木倒下和枯死的情况进行了调查。可以从许多研究中获得可变数据，这些研究分析了木质部性状对不同时间尺度上气候条件的调整。

概要

我们在健康和不健康的树木中观察到了不同的生长方式和木质部导管面积的响应，并草拟了可能适合观察到的方式的水力策略。总体而言，没有出现木质部导管大小作为独立树木健康指标的明确作用。我们表明，木质部性状可能在不同的时间尺度上发生变化，并可能在一定的气候条件下支持地中海树木的性能和健康。我们概述了整个地中海地区木质部性状的地理上的巨大变异性，表明对干旱加剧的反应不一。强调了知识差距和需要的研究领域。