Seedling mortality during biphasic drought in sandy Mediterranean soils
Seedling mortality during biphasic drought in sandy Mediterranean soils
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DOI：
10.1071/fp13366
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发表时间：
2014-01-01
影响因子：
3
通讯作者：
Stevens, Jason C.
中科院分区：
文献类型：
--
作者：
Benigno, Stephen M.;Dixon, Kingsley W.;Stevens, Jason C.
气候变化正在增加干旱的频率和强度，幼苗对反复出现的干旱胁迫模式的反应对于了解植被建立模式是必要的，特别是对于生态恢复和保护项目。一项受控环境研究调查了地中海框架树种的幼苗对模拟连续干旱的生理反应。六个月大的幼苗在 1.0m 高的盆中生长，以模拟深层土壤剖面，并进行充分浇水处理和干旱处理，包括最初 60 天的干旱（停水）、随后 120 天的重新浇水和随后的 60 天的干旱。通过连续收获评估土壤水获取、土壤含水量、最大根深和木质部水势。为了评估幼苗对多次干旱的反应，每次干旱后每 15 天进行一次气体交换和叶绿素荧光测量，并在重新浇水期间进行多次测量。第一次干旱期间没有观察到幼苗死亡，而第二次干旱后 48 天内，所有物种的死亡率均达到 100%。幼苗气体交换和水势随着可用水量的减少而降低，但取决于单个物种的等水或非等水行为。在第二个干旱阶段缺乏持续的光保护会加剧对叶组织的光损伤，导致 g(s) 和叶水势更快地下降。因此，事实证明，双相干旱会降低生理恢复能力，从而不利于幼苗的生长，凸显了未来气候变化预测对地中海生态系统再生能力的严重性。
Climate change is increasing the frequency and intensity of drought, and seedling response to a recurrent pattern of drought stress is necessary to understand vegetation establishment patterns in particularly for ecological restoration and conservation projects. A controlled environment study investigated seedling physiological response of framework Mediterranean tree species to simulated successive droughts. Six-month-old seedlings were grown in 1.0m tall pots to emulate deep soil profiles and subjected to a well watered treatment and a drought treatment consisting of an initial 60 day drought (water withholding), followed by 120 days of re-watering and a subsequent 60 day drought. Soil water access, soil water content, maximum root depth and xylem water potential were assessed through successive harvests. To assess seedling response to multiple droughts, gas-exchange and chlorophyll fluorescence measurements were taken every 15 days after each drought, and multiple times throughout re-watering. No seedling mortality was observed during the initial drought, whereas 100% mortality of all species occurred within 48 days of the second drought. Seedling gas exchange and water potential decreased with decreasing water availability but was dependent on the isohydric or anisohydric behaviour of individual species. An absence of sustained photoprotection during the second drought phase heightened photodamage to foliar tissues resulting in a more rapid decrease of g(s) and leaf water potential. Therefore, biphasic drought proved detrimental to seedling establishment by reducing physiological resilience, highlighting the severity of future climate change predictions towards the regeneration capacity of Mediterranean ecosystems.