Abstract

Fire transforms the structure of natural habitats and, consequently, modifies microclimates affecting ectotherm organisms that are particularly susceptible to changes in the thermal environment. Nevertheless, the effects of fire-induced microclimatic shifts upon natural populations have been neglected. We measured the central tendency and variation of habitat structural and microclimatic variables in experimental plots of Neotropical savanna vegetation subjected to different fire regimes and assessed their effects upon lizard community structure. In addition, we evaluated the underlying mechanisms linking fire-induced environmental changes to community structure, by comparing lizard body condition and survival between different fire regimes. Fire suppression promoted increased tree density, canopy cover and leaf-litter weight, whereas burning had the opposite effects, reducing the habitat structural complexity. The best predictors of fire regimes were means of structural variables, but variances of microclimatic variables, and the reduced structural complexity of burned plots both increased and decreased the variation of microclimatic variables. Lizard community structure was chiefly described by a gradient of decreasing tree density, canopy cover and leaf litter weight with increasing fire severity. About half of the lizard species were favored in the fire-protected plot, while the other half was favored in the burned plots, with most of the variation being explained by structural variables. Lizard body condition and survival rates were not affected by fire regimes, suggesting a dominant role of thermoregulation opportunities afforded by habitat structure—instead of food availability or predation rates—upon community structure. Our findings indicate that even sporadic fires can have profound effects upon lizard communities and that protecting some habitat patches from burning is essential to maximize lizard diversity in Cerrado landscapes.

中文翻译：

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火的长期生境结构和微气候变化影响着塞拉多蜥蜴群落

摘要

火改变了自然栖息地的结构，因此改变了影响外热生物的微气候，这些生物特别容易受到热环境变化的影响。然而，火灾引起的微气候变化对自然种群的影响已被忽略。我们在遭受不同火情的新热带稀树草原植被试验区中测量了栖息地结构和微气候变量的集中趋势和变化，并评估了它们对蜥蜴群落结构的影响。此外，我们通过比较蜥蜴的身体状况和不同火灾情况下的生存情况，评估了将火灾引起的环境变化与社区结构联系起来的潜在机制。灭火抑制了树木的密度，树冠覆盖率和凋落物的重量，而燃烧则相反，降低了栖息地的结构复杂性。火灾状况的最佳预测指标是结构变量的平均值，但微气候变量的方差和烧毁地块结构复杂性的降低既增加又减小了小气候变量的变化。蜥蜴群落结构的主要描述是树木密度降低，冠层覆盖度和凋落物重量随火势的增加而逐渐降低。约有一半的蜥蜴物种在防火地块中受到青睐，而另一半在燃烧的土地中受到青睐，其中大部分变化是由结构变量解释的。蜥蜴的身体状况和生存率不受火灾情况的影响，这表明栖息地结构而非食物供应或捕食率所提供的温度调节机会对社区结构起着主导作用。我们的研究结果表明，即使是零星的大火也可能对蜥蜴群落产生深远的影响，保护某些栖息地免受燃烧对于最大化Cerrado景观中蜥蜴的多样性至关重要。