Fire and herbivory have profound effects on vegetation in savanna ecosystems, but little is known about how different herbivore groups influence vegetation dynamics after fire. We assessed the separate and combined effects of herbivory by cattle and wild meso‐ and megaherbivores on postfire herbaceous vegetation cover, species richness, and species turnover in a savanna ecosystem in central Kenya. We measured these vegetation attributes for five sampling periods (from 2013 to 2017) in prescribed burns and unburned areas located within a series of replicated long‐term herbivore exclosures that allow six different combinations of cattle and wild meso‐ and megaherbivores (elephants and giraffes). Vegetation cover (grasses, mainly) and species richness were initially reduced by burning but recovered by 15–27 months after fire, suggesting strong resilience to infrequent fire. However, the rates of recovery differed in plots accessible by different wild and domestic herbivore guilds. Wildlife (but not cattle) delayed postfire recovery of grasses, and the absence of wildlife (with or without cattle) delayed recovery of forbs. Herbivory by only cattle increased grass species richness in burned relative to unburned areas. Herbivory by cattle (with or without wildlife), however, reduced forb species richness in burned relative to unburned areas. Herbivory by wild ungulates (but not cattle) increased herbaceous species turnover in burned relative to unburned areas. Megaherbivores had negligible modifying effects on these results. This study demonstrates that savanna ecosystems are remarkably resilient to infrequent fires, but postfire grazing by cattle and wild mesoherbivores exerts different effects on recovery trajectories of herbaceous vegetation.

中文翻译：

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野生食草动物和牛对非洲稀树草原火灾后草本植被恢复有不同的影响


火灾和食草对稀树草原生态系统的植被具有深远的影响，但人们对不同的食草动物群体如何影响火灾后的植被动态知之甚少。我们评估了牛和野生中型和大型食草动物的食草对肯尼亚中部稀树草原生态系统火灾后草本植被覆盖、物种丰富度和物种更替的单独和综合影响。我们在五个采样周期（2013 年至 2017 年）的规定烧伤和未烧伤区域测量了这些植被属性，这些区域位于一系列复制的长期食草动物保护区内，这些保护区允许牛和野生中型和大型食草动物（大象和长颈鹿）的六种不同组合。植被覆盖（主要是草）和物种丰富度最初因燃烧而减少，但在火灾后 15 至 27 个月内恢复，这表明对罕见火灾的抵御能力很强。然而，不同野生和家养食草动物协会可进入的地块的恢复率有所不同。野生动物（但不是牛）延迟了草的火灾后恢复，而野生动物（有或没有牛）的缺乏延迟了杂草的恢复。相对于未烧毁地区，仅由牛食草增加了烧毁地区的草物种丰富度。然而，与未烧毁地区相比，牛（有或没有野生动物）的草食性降低了烧毁地区的杂草物种丰富度。与未烧毁地区相比，野生有蹄类动物（但不是牛）的食草增加了烧毁地区的草本物种周转率。大型食草动物对这些结果的影响可以忽略不计。这项研究表明，稀树草原生态系统对于罕见的火灾具有显着的恢复能力，但火灾后牛和野生中食草动物的放牧对草本植被的恢复轨迹产生不同的影响。