Kannenberg Steven A, Phillips Richard P
Department of Biology, Indiana University, Bloomington, IN, 47403, USA.
Oecologia. 2017 Mar;183(3):631-641. doi: 10.1007/s00442-016-3783-2. Epub 2016 Nov 28.
Trees possess myriad adaptations for coping with drought stress, but the extent to which their drought responses are influenced by interactions with soil microbes is poorly understood. To explore the role of microbes in mediating tree responses to drought stress, we exposed saplings of three species (Acer saccharum, Liriodendron tulipifera, and Quercus alba) to a four week experimental drought in mesocosms. Half of the pots were inoculated with a live soil slurry (i.e., a microbial inoculum derived from soils beneath the canopies of mature A. saccharum, L. tulipifera or Q. alba stands), while the other half of the pots received a sterile soil slurry. Soil microbes ameliorated drought stress in L. tulipifera by minimizing reductions in leaf water potential and by reducing photosynthetic declines. In A. saccharum, soil microbes reduced drought stress by lessening declines in leaf water potential, though these changes did not buffer the trees from declining photosynthetic rates. In Q. alba, soil microbes had no effects on leaf physiological parameters during drought stress. In all species, microbes had no significant effects on dynamic C allocation during drought stress, suggesting that microbial effects on plant physiology were unrelated to source-sink dynamics. Collectively, our results suggest that soil microbes have the potential to alter key parameters that are used to diagnose drought sensitivity (i.e., isohydry or anisohydry). To the extent that our results reflect dynamics occurring in forests, a revised perspective on plant hydraulic strategies that considers root-microbe interactions may lead to improved predictions of forest vulnerability to drought.
树木拥有无数应对干旱胁迫的适应性机制，但它们的干旱响应受与土壤微生物相互作用影响的程度却鲜为人知。为了探究微生物在介导树木对干旱胁迫响应中的作用，我们将三种树种（糖枫、北美鹅掌楸和白栎）的树苗置于中型生态箱中进行了为期四周的干旱实验。一半的花盆接种了活的土壤泥浆（即源自成熟糖枫、北美鹅掌楸或白栎林冠下土壤的微生物接种物），而另一半花盆则接种了无菌土壤泥浆。土壤微生物通过最大限度地减少叶片水势的降低和减少光合作用的下降，缓解了北美鹅掌楸的干旱胁迫。在糖枫中，土壤微生物通过减轻叶片水势的下降降低了干旱胁迫，尽管这些变化并未缓冲树木光合速率的下降。在白栎中，土壤微生物在干旱胁迫期间对叶片生理参数没有影响。在所有树种中，微生物在干旱胁迫期间对碳动态分配没有显著影响，这表明微生物对植物生理的影响与源 - 库动态无关。总体而言，我们的结果表明土壤微生物有可能改变用于诊断干旱敏感性的关键参数（即等水线或非等水线）。就我们的结果反映森林中发生的动态而言，一种考虑根 - 微生物相互作用修订后的植物水力策略观点可能会改善对森林干旱脆弱性的预测。
