Savanna woody species evolved with fire. However, the effect of changes in the fire regimes, which tend to increase in the next decades, is not yet fully understood. Here, we tested the effects of increased fire frequency on species richness and the composition of woody plant communities. Specifically, we tested if a high frequency fire management reduces local species richness of communities and homogenizes species composition. We sampled woody plants in 40 sites, distributed in 20 pairs, in Emas National Park (Brazil). Each pair included sites with high fire frequency (firebreaks that are burned annually since 1994) and with natural fire frequency (occurring every 3–5 years). We used a paired t-test to assess effects of the two fire frequency treatments on species richness and permutation tests to compare distance decay in similarity composition and relative abundances. We found that sites with high fire frequency had lower species richness compared to their paired sites subjected to natural fire frequency. However, similarities in species composition among sites with high fire frequency were only slightly higher than among sites subjected to natural fire frequency. The rate of distance decay in similarity was similar on the two treatments. At local scales, the high frequency of fire reduced species richness, an impact that in the long run may be irreversible. However, at broader spatial scales, effects were small as two treatments included similar sets of species. Prescribed fires have the potential to modify the natural dynamics of the woody communities in the savannas we studied. In our study, fire appears to act as a hierarchical filter, selecting species at broader spatial scales and nesting communities at local scales.

稀树草原木本物种随着火而进化。然而，在未来几十年中趋于增加的火灾状况变化的影响尚未完全了解。在这里，我们测试了火灾频率增加对物种丰富度和木本植物群落组成的影响。具体来说，我们测试了高频火灾管理是否会降低社区的当地物种丰富度并使物种组成均匀化。我们在 Emas 国家公园（巴西）的 40 个地点采样了木本植物，分布在 20 对中。每一对都包括火灾频率高（自 1994 年以来每年燃烧的防火带）和自然火灾频率（每 3-5 年发生一次）的地点。我们使用了配对t- 测试评估两种火灾频率处理对物种丰富度的影响，并通过排列测试来比较相似性组成和相对丰度的距离衰减。我们发现，火灾频率高的地点与其遭受自然火灾频率的配对地点相比，物种丰富度较低。然而，火灾频率高的地点之间物种组成的相似性仅略高于自然火灾频率的地点。两种处理的相似性距离衰减率相似。在局部范围内，高频率的火灾减少了物种丰富度，从长远来看，这种影响可能是不可逆转的。然而，在更广泛的空间尺度上，影响很小，因为两种处理包括相似的物种组。规定的火灾有可能改变我们研究的热带稀树草原中木质群落的自然动态。在我们的研究中，火似乎充当了层次过滤器，在更广泛的空间尺度上选择物种并在局部尺度上筑巢群落。