Ant abundance in pitfall traps across different fire treatments

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.

Methods
This dataset consists of ant abundance data collected using pitfall traps at the Territory Wildlife Park fire experiment near Darwin, NT Australia. It was used for an ecology project assessing the effects of fire on ant diversity.

火是全球范围内塑造诸多动物群落的核心生态驱动力。火对动物的影响可分为两类：直接影响（如直接致死个体）与间接影响（如改变植被结构）。而植被结构本身也会调控火的发生频率与强度。因此，动物对火的响应需结合动态的火活动与植被结构来解读。

本研究整合火活动与植被结构相关数据，以期深入理解澳大利亚北部极度易燃的热带稀树草原中，蚂蚁群落对为期17年的控制性火烧处理的响应模式。此前的一项分析显示，经过5年控制性火烧处理后，蚂蚁群落的分异程度有限。因此，本研究首先探究了后续12年火烧处理下蚂蚁群落的分异程度；随后评估了火烧处理、累积火强度（火活动）以及木本植被盖度对蚂蚁物种出现频率、物种丰富度与群落组成的相对贡献。

研究结果表明，即便经过17年的火烧处理，控制性火烧本身对各类蚂蚁响应变量的解释度仍极低。与之形成对比的是，木本植被盖度是所有蚂蚁响应变量的强预测因子，而火活动则对蚂蚁多度与物种丰富度具有中等程度的预测能力。相较于植被盖度较高且火活动较低（或无火活动）的样地，火活动更强的开阔生境中，蚂蚁物种的出现频率与物种丰富度均有所提升。此外，植被盖度高低不同的样地间，蚂蚁群落组成存在显著差异。

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证据。此外，研究结果还表明，由于植被结构与火活动之间的交互作用会产生变异，“均质化”的火烧制度对蚂蚁群落并不会产生均质化的影响。这一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较弱的关联，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。

### 研究方法
本数据集包含在澳大利亚北领地达尔文市附近的领地野生公园火烧实验中，通过陷阱诱捕器（pitfall trap）采集得到的蚂蚁多度数据，该数据曾用于一项评估火对蚂蚁多样性影响的生态学研究项目。