The spatial arrangement of perennial vegetation is critical for ecosystem function in drylands. While much is known about how vegetation patches respond to grazing and abiotic conditions, the size dynamics of individual plants is mostly limited to theoretical studies. We measured the size distribution (mean, variance, skewness) and density of individual grasses, and grass species composition at 451 sites spanning a range of grazing intensities across three broad vegetation communities in semi‐arid eastern Australia. We assessed the relative role of grazing by livestock (cattle and sheep), native (kangaroos) and introduced (rabbits) free ranging herbivores, and several environmental measures (productivity, diversity, composition and groundstorey plant cover) on the size distribution and density of individual grasses. We found mean grass size and density were more sensitive to shifts in grazing intensity and environmental conditions than size variance or the frequency of the smallest individuals (skewness), and shifts were mostly driven by site productivity and cattle and kangaroo grazing. Sheep grazing only reduced mean grass size, and rabbit grazing had no consistent effects. Importantly, we found that site productivity and species composition altered the impacts of grazing on grass density and size distribution. For example, increasing cattle grazing led to larger grasses in low productivity sites. It also led to larger, denser, more variable‐sized grasses among grass species from sites with finer soil texture. Increasing kangaroo grazing led to smaller, denser individuals among grass species from sites with coarse soil texture. At high diversity sites kangaroo grazing led to denser, more homogenised grass sizes with a lower frequency of small individuals. Understanding the in situ response of individual plant sizes gives us insights into the processes driving shifts in perennial vegetation patchiness, improving our ability to predict how the spatial arrangement of ecosystems might change under global change scenarios.

中文翻译：

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放牧和生产力改变半干旱林地中个体草地的大小动态

多年生植物的空间布局对于干旱地区的生态系统功能至关重要。尽管人们对植被斑块如何响应放牧和非生物条件已广为人知，但单个植物的大小动态主要限于理论研究。我们测量了单个草的大小分布（均值，方差，偏度）和密度，以及在澳大利亚东部半干旱地区三个广泛的植被群落中的451个地点的草种组成，这些地点跨越了一系列放牧强度。我们评估了放牧的牲畜（牛和羊），土生的（袋鼠）和放牧的（家兔）放牧食草动物的相对作用，以及几种环境措施（生产力，多样性，组成和地面植物覆盖度）对放牧的规模和密度的影响。个别草。我们发现，平均草皮大小和密度对放牧强度和环境条件的变化比大小变化或最小个体的频率（偏度）更敏感，而这种变化主要由站点生产力以及牛和袋鼠放牧驱动。放牧绵羊只会减少平均草皮大小，而兔子放牧则不会产生一致的影响。重要的是，我们发现场地生产力和物种组成改变了放牧对草密度和大小分布的影响。例如，越来越多的牛放牧导致低生产力地区的草丛更大。这还导致土壤质地较细的草种中的草更大，更密，大小更多。袋鼠放牧的增加导致土壤质地粗糙的草种中个体更小，更密集。在高度多样性的地方，袋鼠放牧导致草密度更高，更均一化，小型个体的频率更低。了解单个植物大小的原位响应可以使我们深入了解多年生植被斑块变化的过程，从而提高我们预测在全球变化情况下生态系统空间布局可能如何变化的能力。