Thermal limits of leaf metabolism across biomes

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• 作者：Odhran S. O'sullivan ; Mary A. Heskel ; Peter B. Reich ; Mark G. Tjoelker ; Lasantha K. Weerasinghe ; Aurore Penillard ; Lingling Zhu ; John J. G. Egerton ; Keith J. Bloomfield ; Danielle Creek ; Nur H. A. Bahar ; Kevin L. Griffin ; Vaughan Hurry ; Patrick Meir ; Matthew H. Turnbull and Owen K. Atkin
• 刊名：Global Change Biology
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：23
• 期：1
• 页码：209-223
• 全文大小：514K
• ISSN：1365-2486

文摘

High-temperature tolerance in plants is important in a warming world, with extreme heat waves predicted to increase in frequency and duration, potentially leading to lethal heating of leaves. Global patterns of high-temperature tolerance are documented in animals, but generally not in plants, limiting our ability to assess risks associated with climate warming. To assess whether there are global patterns in high-temperature tolerance of leaf metabolism, we quantified T_crit (high temperature where minimal chlorophyll a fluorescence rises rapidly and thus photosystem II is disrupted) and T_max (temperature where leaf respiration in darkness is maximal, beyond which respiratory function rapidly declines) in upper canopy leaves of 218 plant species spanning seven biomes. Mean site-based T_crit values ranged from 41.5 °C in the Alaskan arctic to 50.8 °C in lowland tropical rainforests of Peruvian Amazon. For T_max, the equivalent values were 51.0 and 60.6 °C in the Arctic and Amazon, respectively. T_crit and T_max followed similar biogeographic patterns, increasing linearly (˜8 °C) from polar to equatorial regions. Such increases in high-temperature tolerance are much less than expected based on the 20 °C span in high-temperature extremes across the globe. Moreover, with only modest high-temperature tolerance despite high summer temperature extremes, species in mid-latitude (~20–50°) regions have the narrowest thermal safety margins in upper canopy leaves; these regions are at the greatest risk of damage due to extreme heat-wave events, especially under conditions when leaf temperatures are further elevated by a lack of transpirational cooling. Using predicted heat-wave events for 2050 and accounting for possible thermal acclimation of T_crit and T_max, we also found that these safety margins could shrink in a warmer world, as rising temperatures are likely to exceed thermal tolerance limits. Thus, increasing numbers of species in many biomes may be at risk as heat-wave events become more severe with climate change.