Drought is often discussed as a major perturbation in savanna ecosystems, associated with lasting shifts in savanna structure and functioning. However, historically, droughts have occurred frequently in southern African savannas, suggesting that plants might benefit from being resilient to drought. Here, we evaluate whether the 2014–2016 drought was an extreme event in terms of effects on the herbaceous vegetation and specifically on grasses. We monitored herbaceous responses, pre-, during and post-drought in the Kruger National Park and compared responses with a previous extreme drought (1991–1992). Grass biomass decreased during both droughts, but recovered quickly once rains returned, regardless of whether areas burned in the years preceding drought. However, species functional composition was slower to recover, with shifts in dominance that closely matched grass photosynthetic machinery. Species drought tolerances were best predicted by their bundle sheath morphology: species characterised by XyMS− bundle sheaths (often associated with NADP-ME photosythesis) declined in abundance consistently during drought, whereas those characterised by XyMS+ bundle sheaths (associated with PEP-ck and NAD-ME photosynthesis) either increased or were unaffected by drought. The response of grass to drought, at least in terms of productivity and functional composition, is relatively predictable.

中文翻译：

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草群落对非洲大草原干旱的反应

干旱通常被认为是稀树草原生态系统的主要扰动，与稀树草原结构和功能的持久变化有关。然而，从历史上看，南部非洲大草原经常发生干旱，这表明植物可能受益于抗旱能力。在这里，我们评估 2014-2016 年干旱是否是对草本植被特别是草类的影响的极端事件。我们监测了克鲁格国家公园干旱前、干旱期间和干旱后的草本反应，并将反应与之前的极端干旱（1991-1992）进行了比较。在两次干旱期间，草生物量均下降，但一旦降雨恢复，草生物量就会迅速恢复，无论干旱前几年地区是否被烧毁。然而，物种功能组成恢复较慢，与草光合作用机制密切匹配的优势转移。物种耐旱性最好通过它们的束鞘形态来预测：以 XyMS-束鞘（通常与 NADP-ME 光合作用）为特征的物种在干旱期间丰度持续下降，而那些以 XyMS+束鞘（与 PEP-ck 和 NAD 相关）为特征的物种-ME 光合作用）增加或不受干旱影响。草对干旱的反应，至少在生产力和功能组成方面，是相对可预测的。而以 XyMS+ 束鞘（与 PEP-ck 和 NAD-ME 光合作用相关）为特征的那些要么增加要么不受干旱影响。草对干旱的反应，至少在生产力和功能组成方面，是相对可预测的。而以 XyMS+ 束鞘（与 PEP-ck 和 NAD-ME 光合作用相关）为特征的那些要么增加要么不受干旱影响。草对干旱的反应，至少在生产力和功能组成方面，是相对可预测的。