Arid ecosystems are strongly limited by water availability, and precipitation plays a major role in the dynamics of all species in arid regions, as well as the ecosystem processes that occur there. However, understanding how biotic interactions mediate long‐term responses of dryland ecosystems to rainfall remains very fragmented. We report on a unique large‐scale field experiment spanning 25 yr and three trophic levels (plants, small mammal herbivores, predators) in a dryland ecosystem in the northern Chilean Mediterranean Region where we assessed how biotic interactions influence the long‐term plant community responses to precipitation. As the most persistent ecological changes in dryland systems may result from changes in the structure, cover, and composition of the perennial vegetation, we emphasized the interplay between bottom‐up and top‐down controls of perennial plants in our analyses. Rainfall was the primary factor affecting the dynamics of, and interactions among, plants and small mammals. Ephemeral plant cover dynamics closely tracked short‐term annual rainfall, but seemed unaffected by top‐down controls (herbivory). In contrast, the response of the perennial plant cover to precipitation was mediated by (1) a complex interplay between subtle top‐down (herbivory) controls that become more apparent in the long‐term, (2) competition with ephemeral plants during wet years, and (3) an indirect effect of predators on subdominant shrubs and perennial herbs. This long‐term field experiment highlights how climate‐induced responses of arid perennial vegetation are influenced by interactions across trophic levels and temporal scales. In the face of global change, understanding how multi‐trophic controls mediate dryland vegetation responses to climate is essential to properly managing the conservation of biodiversity in arid systems.

中文翻译：

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营养层间的物种相互作用介导降雨对旱地植被动态的影响

干旱的生态系统受到水资源的严重限制，而降水在干旱地区所有物种的动态以及那里发生的生态系统过程中起着重要作用。但是，了解生物相互作用如何介导旱地生态系统对降雨的长期响应仍然十分零散。我们报告了智利北部地中海地区干旱地区生态系统中跨越25年和三个营养水平（植物，小型哺乳动物食草动物，捕食者）的独特大规模实地实验，我们在该实验中评估了生物相互作用如何影响长期植物群落反应去沉淀。由于旱地系统中最持久的生态变化可能是多年生植被的结构，覆盖度和组成发生变化的结果，我们在分析中强调了多年生植物自下而上和自上而下的控制之间的相互作用。降雨是影响植物和小型哺乳动物动力及其相互作用的主要因素。临时植物的覆盖动态密切跟踪短期年度降雨，但似乎不受自上而下的控制（食草动物）的影响。相比之下，多年生植物覆盖对降水的响应是由以下因素介导的：（1）细微的自上而下（食草动物）控制之间的复杂相互作用在长期中变得更加明显；（2）湿润时期与短暂植物的竞争（3）捕食者对主要灌木和多年生草本植物的间接影响。这项长期的野外实验强调了营养水平和时间尺度上的相互作用如何影响干旱多年生植被的气候诱导响应。面对全球变化，了解多营养控制如何调节旱地植被对气候的响应对于正确管理干旱系统中的生物多样性保护至关重要。