Purpose of Review

Harsher abiotic conditions are projected for many woodland areas, especially in already arid and semi-arid climates such as the Southwestern USA. Stomatal regulation of their aperture is one of the ways plants cope with drought. Interestingly, the dominant species in the Southwest USA, like in many other ecosystems, have different stomatal behaviors to regulate water loss ranging from isohydric (e.g., piñon pine) to anisohydric (e.g., juniper) conditions suggesting a possible niche separation or different but comparable strategies of coping with stress. The relatively isohydric piñon pine is usually presumed to be more sensitive to drought or less desiccation tolerant compared to the anisohydric juniper although both species close their stomata under drought to avoid hydraulic failure, and the mortality of one species (mostly piñon) over the other in the recent droughts can be attributed to insect outbreaks rather than drought sensitivity alone. Furthermore, no clear evidence exists demonstrating that iso- or anisohydric strategy increases water use efficiency over the other consistently. How these different stomatal regulatory tactics enable woody species to withstand harsh abiotic conditions remains a subject of inquiry to be covered in this review.

Recent Findings

This contribution reviews and explores the use of simplified stomatal optimization theories to assess how photosynthesis and transpiration respond to warming (H), drought (D), and combined warming and drought (H+D) for isohydric and anisohydric woody plants experiencing the same abiotic stressors. It sheds light on how simplified stomatal optimization theories can separate between photosynthetic and hydraulic acclimation due to abiotic stressors and how the interactive effects of H+D versus H or D alone can be incorporated into future climate models.

Summary

The work here demonstrates how field data can be bridged to simplified optimality principles so as to explore the effect of future changes in temperature and in soil water content on the acclimation of tree species with distinct water use strategies. The results show that the deviations between measurements and predictions from the simplified optimality principle can explain different species’ acclimation behaviors.

中文翻译：

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在干燥和变暖的气候下将植物的水和碳经济联系起来

审查目的

预计许多林地地区的非生物条件将更加恶劣，特别是在美国西南部等已经干旱和半干旱的气候地区。气孔孔径调节是植物应对干旱的方式之一。有趣的是，美国西南部的优势物种，与许多其他生态系统一样，具有不同的气孔行为来调节水分流失，范围从等水（例如松树）到非等水（例如杜松）条件，这表明可能存在生态位分离或不同但可比的情况应对压力的策略。与不等水杜松相比，相对等水的松树通常被认为对干旱更敏感或耐干燥性较差，尽管这两个物种在干旱下都会关闭气孔以避免水力衰竭，并且一种物种（主要是松树）的死亡率高于另一种树种最近的干旱可归因于昆虫爆发，而不仅仅是干旱敏感性。此外，没有明确的证据表明等水或非等水策略比其他策略能够持续提高用水效率。这些不同的气孔调节策略如何使木本物种能够承受恶劣的非生物条件仍然是本综述要探讨的一个主题。

最近的发现

本文回顾并探索了使用简化的气孔优化理论来评估经历相同非生物的等水和非等水木本植物的光合作用和蒸腾如何响应变暖（H）、干旱（D）以及变暖和干旱联合（H+D）压力源。它揭示了简化的气孔优化理论如何区分非生物胁迫引起的光合适应和水力适应，以及如何将 H+D 与单独的 H 或 D 的相互作用效应纳入未来的气候模型。

概括

这里的工作展示了如何将现场数据与简化的最优原则联系起来，以探索未来温度和土壤含水量的变化对具有不同用水策略的树种的适应的影响。结果表明，测量结果与简化最优原理预测之间的偏差可以解释不同物种的适应行为。