Native grasslands have been vastly transformed with the expansion of human activities. Applied fire regimes offer conservation-based management an opportunity to enhance remaining grassland biodiversity and secure its persistence into the future. Fire regimes have complex interactions with abiotic and biotic ecosystem components that influence environmental heterogeneity and biodiversity. We examined the pyrodiversity–biodiversity hypothesis, which suggests that more species are supported where pyrodiversity, that is, the level of environmental heterogeneity associated with different fire regimes, is greater. A mesocosm-type field experiment, maintained for 38 yr, was used to determine the response of plant diversity to 1-, 2-, 5- and 12-yr fire-return interval treatments, with early-dormant, middormant and early–growing season burns. Our sampling regime was designed to assess the influence of fire treatments and combinations thereof, over spatial scale, on plant diversity. Pyrodiversity was maximized where fire regime diversity, simulated by varying the size of patches with different fire treatments, was greatest. Species richness was predicted to be reduced at short and long extremes of fire-return interval, as suggested by the intermediate-disturbance hypothesis. The influence of fire treatments on alpha and beta diversity, and plant functional groups, were tested using multivariate and Bayesian models. Multilevel models of plant height and growth form, with fire-return interval, reflected the strong indirect influence of fire-return interval on sward structure and the plant environment. The pyrodiversity–biodiversity and intermediate-disturbance hypotheses were only partially supported and depended on the plant group and spatial scale of assessment. Although both frequent and infrequent burns made important contributions to overall species richness, richness peaked where 20–40% of the area was protected from frequent fires. The larger contribution of frequent burning to diversity was due to an interaction with scale and forb turnover over the trial area. Extremes in fire-return intervals reduced forb richness, supporting the predictions of the intermediate-disturbance hypothesis. Spring burns had a weak negative influence on forb alpha diversity, but only at small scales. For a meaningful contribution of management to plant diversity, traditional fixed biennial burns need to be supplemented with smaller patches burned with longer fire-return intervals, and extremes in fire-return intervals avoided.

中文翻译：

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草原生物多样性热点地区火灾的几十年影响：火成多样性会增强植物多样性吗？

随着人类活动的扩大，原生草原发生了巨大的变化。应用火灾制度为基于保护的管理提供了一个机会，以增强剩余的草原生物多样性并确保其在未来的持久性。火灾状态与影响环境异质性和生物多样性的非生物和生物生态系统成分具有复杂的相互作用。我们研究了火热多样性-生物多样性假说，这表明在火热多样性（即与不同火灾状态相关的环境异质性水平）更大的地方支持更多的物种。使用维持 38 年的中宇宙型田间试验来确定植物多样性对 1 年、2 年、5 年和 12 年的回火间隔处理的响应，包括早期休眠、中期休眠和早期生长季节灼伤。我们的抽样制度旨在评估火灾处理及其组合在空间尺度上对植物多样性的影响。在通过改变具有不同火灾处理的斑块大小来模拟的火灾状态多样性最大的地方，火势多样性最大化。正如中间扰动假说所暗示的那样，预计物种丰富度将在短期和长期极端火回期间减少。使用多变量和贝叶斯模型测试了火灾处理对 α 和 β 多样性以及植物功能组的影响。植物高度和生长形态的多层次模型，带有回火间隔，反映了回火间隔对草坪结构和植物环境的强烈间接影响。热多样性-生物多样性和中间干扰假设仅得到部分支持，并取决于植物群和评估的空间尺度。尽管频繁和不频繁的烧伤都对整体物种丰富度做出了重要贡献，但丰富度在 20-40% 的地区免受频繁火灾的影响时达到顶峰。频繁燃烧对多样性的更大贡献是由于与试验区规模和禁林营业额的相互作用。火灾返回间隔的极端降低了丰富性，支持了中间干扰假设的预测。春季烧伤对 forb alpha 多样性的负面影响较弱，但仅在小范围内。为了使管理对植物多样性做出有意义的贡献，