Data from: Ant abundance in pitfall traps across different fire treatments
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Fire is a dominant ecological force shaping many faunal communities globally. Fire affects faunaeither directly, such as by killing individuals, or indirectly, such as by modifying vegetation structure. Vegetation structure itself also modulates fire frequency and intensity. As such, faunal responses to fire need to be seen through the lens of variable fire activity and vegetation structure. Here, we incorporate information on fire activity and vegetation structure to enhance an understanding of the response of ants to long-term (17-year) experimental fire treatments in an extremely fire-prone tropical savanna in northern Australia. A previous analysis revealed limited divergence in ant communities after five years of experimental fire treatment. Hence, we first investigated the extent to which ant communities diverged over a subsequent 12 years of treatment. We then assessed the relative contribution of fire treatment, cumulative fire intensity(fire activity) and woody cover to responses of ant species frequency of occurrence, richness and composition. We found that, even after 17 years, fire treatments explained little variation in any ant response variable. In contrast, woody cover was a strong predictor for all of them, while fire activity was a moderate predictor for abundance and richness. Ant species occurrence and richness increased in open habitats receiving higher levels of fire activity, compared with plots with higher vegetation cover experiencing low (or no) fire activity. Moreover, species composition differed between plots with high and low vegetation cover. Our findings provide experimental support to the principle that the effects of fire on fauna are primarily indirect, via its effect on vegetation structure. Furthermore, our results show that a ‘uniform’ fire regime does not have uniform impacts on the ant fauna, because of variability imposed by interactions between vegetation structure and fire activity. This helps explain why there is often a weak relationship between pyrodiversity and biodiversity, and it lessens the need for active management of pyrodiversity to maintain biodiversity.
火是塑造全球众多动物群落（faunal communities）的主导性生态驱动力。火对动物群落的影响可分为两类路径：直接路径如直接杀死个体，间接路径如改变植被结构。而植被结构本身亦可调控火的发生频率与强度。因此，针对火的动物群落响应研究，需置于动态火活动与植被结构的交互框架下开展。本研究整合火活动与植被结构相关数据，以深化对澳大利亚北部极端易火热带稀树草原（tropical savanna）中，蚁类对长达17年的控制性火烧试验（experimental fire treatments）响应的认知。此前一项分析显示，经过5年控制性火烧处理后，蚁类群落的分化程度有限。据此，我们首先探究了后续12年火烧处理下蚁类群落的分化程度；随后评估了火烧处理、累积火强度（fire activity）与木本覆盖度（woody cover）对蚁类物种出现频率、物种丰富度与物种组成的相对贡献。研究发现，即便历经17年，火烧处理对任一蚁类响应变量的解释度均较低。与之形成鲜明对比的是，木本覆盖度是所有响应变量的强预测因子，而火活动则是蚁类个体多度与物种丰富度的中等强度预测因子。相较于植被覆盖度较高、火活动较低（或无火活动）的样地，火活动水平更高的开阔生境中，蚁类物种出现频率与物种丰富度均显著提升。此外，高、低植被覆盖度样地的蚁类物种组成存在显著差异。本研究结果为“火对动物的影响主要通过改变植被结构产生间接作用”这一核心原理提供了实验支撑。进一步而言，我们的结果表明，“同质化”火制度对蚁类动物群落的影响并非同质化，这源于植被结构与火活动之间的相互作用所带来的变异。该发现有助于解释为何火多样性（pyrodiversity）与生物多样性之间往往仅存在微弱关联，同时也降低了通过主动调控火多样性以维持生物多样性的必要性。
