Disturbance often increases local‐scale (α) diversity by suppressing dominant competitors. However, widespread disturbances may also reduce biotic heterogeneity (β diversity) by making the identities and abundances of species more similar among patches. Landscape‐scale (γ) diversity may also decline if disturbance‐sensitive species are lost. California’s vernal pool plant communities are species rich, in part because of two scales of β diversity: (1) within pools, as species composition changes with depth (referred to here as vertical β diversity), and (2) between pools, in response to dispersal limitation and variation in pool attributes (referred to here as horizontal β diversity). We asked how grazing by livestock, a common management practice, affects vernal pool plant diversity at multiple hierarchical spatial scales. In terms of abundance‐weighted diversity, grazing increased α both within local pool habitat zones and at the whole‐pool scale, as well as γ at the pasture scale without influencing horizontal or vertical β diversity. In terms of species richness, increases in α diversity within habitat zones and within whole pools led to small decreases in horizontal β diversity as species occupancy increased. This had a dampened effect on species richness at the γ (pasture) scale without any loss of disturbance‐sensitive species. We conclude that grazing increases species richness and evenness (α) by reducing competitive dominance, without large disruptions to the critical spatial heterogeneity (β) that generates high landscape‐level diversity (γ).

中文翻译：

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放牧会影响加利福尼亚州春季水池中的植被多样性和异质性

干扰通常会通过压制主要竞争者来增加本地规模（α）的多样性。但是，广泛的干扰还可能通过使斑块之间的物种身份和丰富度更加相似来降低生物异质性（β多样性）。如果对干扰敏感的物种丧失，景观尺度（γ）多样性也可能下降。加利福尼亚州的春季池植物群落物种丰富，部分原因是β多样性有两个尺度：（1）池内，物种组成随深度而变化（此处称为垂直β多样性），以及（2）池之间的响应限制池属性的散布限制和变化（此处称为水平β分集）。我们询问了牲畜放牧（一种常见的管理做法）如何在多个层次的空间尺度上影响春季池植物的多样性。就丰度加权多样性而言，放牧增加了当地水池栖息地区域内和整个水池规模内的α，以及牧场规模上的γ，而不会影响水平或垂直β多样性。就物种丰富度而言，随着物种占有率的增加，栖息地区域内和整个水池内α多样性的增加导致水平β多样性的小幅下降。这在γ（草场）规模上对物种丰富度产生了衰减作用，而没有任何对干扰敏感的物种的损失。我们得出结论，放牧通过减少竞争优势来增加物种的丰富度和均匀度（α），