Department of Biology, University of Florida, PO Box 118525, Gainesville, FL, 32611-8525, USA.
Oecologia. 2012 Apr;168(4):997-1012. doi: 10.1007/s00442-011-2130-x. Epub 2011 Oct 11.
Disturbance is a major source of spatial and temporal heterogeneity. In fire-maintained systems, disturbance by fire is often used as a management tool to increase biological diversity, restore degraded habitats, and reduce pest outbreaks. Much attention has been given to how plant communities recover from fire, but relatively few studies have examined post-fire responses of higher order species, such as insect herbivores. Because dynamic feedbacks occur between plants and their consumers, which can in turn influence the response of the entire ecosystem, incorporating higher trophic level responses into our understanding of the effects of fire is essential. In this study, we used structural equation modeling (SEM) to tease apart the direct and indirect effects of fire on insect herbivore assemblages found on three common oak species in the Florida scrub (Quercus inopina, Q. chapmanii, and Q. geminata). We investigated how fire affected herbivore abundance, richness, and community composition both directly and indirectly through environmental heterogeneity at different spatial scales (e.g., leaf quality, plant architecture, and habitat structure). We also investigated how seasonality and landscape heterogeneity influenced post-fire responses of insect herbivores and whether fire effects on herbivore assemblages varied among different host plants. Our general findings were that fire effects were (1) largely indirect, mediated through habitat structure (although direct fire effects were observed on Q. inopina herbivores), (2) non-linear through time due to self-thinning processes occurring in the scrub habitat, and (3) varied according to herbivore assemblage as a result of differences in the composition of species in each herbivore community. To the best of our knowledge, this is the first comprehensive study to examine how fire influences the assembly of insect herbivore communities through both direct and indirect pathways and at multiple spatial scales.
干扰是时空异质性的主要来源。在以火为主导的系统中，火干扰通常被用作一种管理工具，以增加生物多样性、恢复退化的栖息地和减少害虫爆发。人们已经关注了植物群落如何从火灾中恢复，但相对较少的研究考察了更高层次的物种（如昆虫食草动物）在火灾后的反应。由于植物与其消费者之间存在动态反馈，这反过来又会影响整个生态系统的反应，因此将更高营养级别的反应纳入我们对火灾影响的理解是至关重要的。在这项研究中，我们使用结构方程模型（SEM）来梳理火灾对佛罗里达州灌丛中三种常见栎属植物（Q. inopina、Q. chapmanii 和 Q. geminata）上昆虫食草动物组合的直接和间接影响。我们研究了火灾如何通过不同空间尺度上的环境异质性（例如叶片质量、植物结构和栖息地结构）直接和间接影响食草动物的丰度、丰富度和群落组成。我们还研究了季节性和景观异质性如何影响昆虫食草动物的火灾后反应，以及火灾对食草动物组合的影响是否因不同宿主植物而有所不同。我们的总体发现是，火灾的影响（1）主要是间接的，通过栖息地结构介导（尽管在 Q. inopina 食草动物上观察到直接火灾影响），（2）由于灌丛栖息地中发生的自疏过程，随时间呈非线性变化，以及（3）由于每个食草动物群落中物种组成的差异而有所不同。据我们所知，这是第一项全面研究，考察了火灾如何通过直接和间接途径以及在多个空间尺度上影响昆虫食草动物群落的组装。
