Spatially patchy fire creates landscape-level diversity that in turn stabilizes several rangeland ecosystem services, including forage production and habitat availability. To enhance biodiversity and livestock production, efforts are underway to restore fire regimes in rangelands throughout the Great Plains. However, invasive species such as tall fescue Schedonorus arundinaceus syn. Festuca arundinacea, initially introduced for forage production, hamper prescribed fire use. Grazer density, or stocking rate, modulates the effect of patchy fire regimes on ecological patterns in invaded, semi-natural rangeland pastures. We compare three diversity–stability responses—temporal variability in aboveground plant biomass, portfolio effects among plant functional groups, and beta diversity in plant functional group composition—in pastures managed with two different fire regimes through three periods of heavy, light, and moderate stocking rate in southern Iowa, USA. Pastures were either burned in patches, with one-third of the pasture burned each year, or completely burned every third year. The period of moderate grazer density had the least temporal variability in aboveground plant biomass, regardless of fire regime. We also found statistical evidence for a portfolio effect under moderate stocking, where diversification of plant communities through varying cover of functional groups can stabilize communities by reducing year-to-year variability. Beta diversity among plant functional groups was greatest during the moderate grazer density period as well. The short stature of tall fescue prevented the patch-burning regime to create contrast in vegetation structure among patches, and there was no difference in any diversity–stability mechanism response across the two different patterns of burning. Although longitudinal, these data suggest that temporal variability in aboveground plant biomass declines with diversity–stability mechanisms that underlie ecosystem function. Our results also support a decades-old principle of range management: moderate grazing intensity enhances diversity and stability, which has been shown to buffer forage shortfalls during drought.

中文翻译：

---

在低矮的草原上，适中的Grazer密度比草料燃烧更稳定草料的供应

空间上零散的大火创造了景观层面的多样性，进而稳定了多种牧场生态系统服务，包括牧草生产和栖息地可用性。为了提高生物多样性和畜牧生产，正在努力恢复大平原整个牧场的火势。但是，入侵物种如高羊茅Schedonorus arundinaceus syn。羊茅，最初是为草料生产引入的，阻碍了规定的消防用途。放牧者的密度或放养率调节着斑驳的火势对被入侵的半自然牧场的生态格局的影响。我们比较了三种不同的稳定性响应（地上植物生物量的时间变异性，植物功能群之间的组合效应以及植物功能群组成的β多样性）在通过两种不同火情管理的草地上，通过重，轻和中度放养的三个时期进行管理的牧场美国爱荷华州南部的房价 牧场要么被成片燃烧，每年有三分之一的牧场被燃烧，或者每三年被完全燃烧。无论火情如何，中等放牧者密度的时期地上植物生物量的时间变化最小。我们还发现了适度放养下的投资组合效应的统计证据，通过适度放养，植物群落的多样化通过覆盖不同的功能组可以通过减少年度差异来稳定群落。在适度的放牧者密度期间，植物功能组之间的Beta多样性也最大。高矮羊茅的矮小身形阻止了斑块燃烧状态在斑块之间的植被结构中形成对比，并且在两种不同燃烧模式下，任何多样性-稳定性机制的响应都没有差异。尽管是纵向的，但这些数据表明，地上植物生物量的时间变异性随着生态系统功能基础的多样性-稳定性机制而下降。我们的结果也支持了数十年的范围管理原则：