Drought timing, not previous drought exposure, determines sensitivity of two shortgrass species to water stress
Drought timing, not previous drought exposure, determines sensitivity of two shortgrass species to water stress
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DOI：
10.1007/s00442-018-4265-5
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发表时间：
2018-09
期刊：
影响因子：
2.7
通讯作者：
N. Lemoine;R. Griffin‐Nolan;Abigail D. Lock;A. Knapp
中科院分区：
文献类型：
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作者：
N. Lemoine;R. Griffin‐Nolan;Abigail D. Lock;A. Knapp
气候变化将改变全球降水模式，使我们了解更频繁和更严重的干旱将如何影响生态系统变得越来越重要。然而，大多数干旱研究都是针对单一的季节内干旱，我们对单一生长季节内发生的多重干旱的影响知之甚少。这一区别很重要，因为许多植物物种能够适应生理环境，因此多次干旱对生态系统功能的影响与累积的独立干旱的影响有很大差异。不幸的是，我们对半干旱草原等干旱敏感生态系统中优势物种适应干旱的能力知之甚少。在这里，我们测试了两个占主导地位的短草草原物种：Bouteloua gracilis（C4）和Elymoides（C3）的生理适应多个干旱事件。两个物种都没有表现出生理适应干旱，叶水势，气孔导度，光合速率都受到了同样的影响，由一个单一的，后期干旱和第二，后期干旱。生物量最低的植物暴露于两次干旱，但这可能是由于早期和后期干旱的累积效应。我们的研究结果表明，后期干旱对两种优势短草的生物量生产产生较弱的影响，但较弱的影响是由于植物生理的个体发生变化，而不是对多次干旱的生理适应。因此，目前的生态系统模型，包括草物候和季节生理学应提供准确的预测初级生产在未来的气候。
Climate change will alter global precipitation patterns, making it increasingly important that we understand how ecosystems will be impacted by more frequent and severe droughts. Yet most drought studies examine a single, within-season drought, and we know relatively little about the impacts of multiple droughts that occur within a single growing season. This distinction is important because many plant species are able to acclimate physiologically, such that the effects of multiple droughts on ecosystem function deviate significantly from the effects of cumulative, independent droughts. Unfortunately, we know relatively little about the ability of dominant species to acclimate to drought in drought-sensitive ecosystems like semi-arid grasslands. Here, we tested for physiological acclimation to multiple drought events in two dominant shortgrass steppe species:Bouteloua gracilis(C4) andElymus elymoides(C3). Neither species exhibited physiological acclimation to drought; leaf water potential, stomatal conductance, and photosynthesis rates were all similarly affected by a single, late period drought and a second, late period drought. Biomass was lowest in plants exposed to two droughts, but this is likely due to the cumulative effects of both an early and late period drought. Our results suggest that late period droughts do exert weaker effects on biomass production of two dominant shortgrass species, but that the weaker effects are due to ontogenetic changes in plant physiology as opposed to physiological acclimation against multiple droughts. As a consequence, current ecosystem models that incorporate grass phenology and seasonal physiology should provide accurate predictions of primary production under future climates.