Rainfall and herbivory shape savannah herbaceous communities, but these disturbances are being altered globally. To assess potential consequences of such alterations, we evaluated herbivore effects on species and functional diversity during an episodic drought in a sodic savannah using data collected from long‐term herbivore exclosures in the Kruger National Park, South Africa. Herbaceous life forms are rarely acknowledged as distinct functional entities. Moreover, the functional ecology of forbs remains elusive. Here, we present disturbances–responses by forbs separately from grasses. We hypothesised that combinations of intense utilisation and drought would be associated with low diversity and high dominance at species and functional levels for both life forms. Contrary to our hypothesis, low forb and grass diversity was associated with long‐term herbivore exclusion, which exceeded expected undesirable effects of intense utilisation and drought. Grasses responded less sensitively, suggesting that forbs respond dynamically to changes in herbivore assemblage when these alterations are combined with drought. Consistent with patterns in savannah systems, forbs contributed significantly to species and functional trait diversity. High forb diversity is suggested to enhance resilience of this nutrient‐rich ecosystem against declines in its functioning when subjected to drought and alterations in herbivory.

中文翻译：

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草食动物排斥对福布斯多样性的影响：干旱期间物种和功能响应的比较

降雨和食草形成了热带稀树草原的草本群落，但是这些干扰正在全球范围内被改变。为了评估此类改变的潜在后果，我们使用从南非克鲁格国家公园的长期食草动物遗迹收集的数据，评估了草食动物对苏打大草原的偶发干旱期间物种和功能多样性的影响。草本生命形式很少被认为是独特的功能实体。此外，前叉的功能生态学仍然难以捉摸。在这里，我们提出了干扰-杂草与草分别产生的干扰。我们假设，高强度利用和干旱的结合将导致两种生命形式在物种和功能水平上的低多样性和高优势地位。与我们的假设相反，低的草和草的多样性与长期的草食动物排斥有关，超过了集约利用和干旱的预期不良影响。草的反应较不灵敏，表明当这些改变与干旱相结合时，草对草食动物组合的变化具有动态响应。与稀树草原系统的模式一致，Forbs对物种和功能性状的多样性做出了重要贡献。建议在干旱和食草动物发生变化时，高分叉多样性可增强这种营养丰富的生态系统的抵御能力，以防止其功能下降。提示当这些改变与干旱结合时，草对草食动物组合的变化有动态的反应。与稀树草原系统的模式一致，Forbs对物种和功能性状的多样性做出了重要贡献。建议在干旱和食草动物发生变化时，高分叉多样性可增强这种营养丰富的生态系统的抵御能力，以防止其功能下降。提示当这些改变与干旱结合时，草对草食动物组合的变化有动态的反应。与稀树草原系统的模式一致，Forbs对物种和功能性状的多样性做出了重要贡献。建议在干旱和食草动物发生变化时，高分叉多样性可增强这种营养丰富的生态系统的抵御能力，以防止其功能下降。