Foster C N, Barton P S, Wood J T, Lindenmayer D B
Fenner School of Environment and Society, The Australian National University, Acton, ACT, 2601, Australia,
Oecologia. 2015 Sep;179(1):237-48. doi: 10.1007/s00442-015-3323-5. Epub 2015 May 3.
Altered disturbance regimes are a major driver of biodiversity loss worldwide. Maintaining or re-creating natural disturbance regimes is therefore the focus of many conservation programmes. A key challenge, however, is to understand how co-occurring disturbances interact to affect biodiversity. We experimentally tested for the interactive effects of prescribed fire and large macropod herbivores on the web-building spider assemblage of a eucalypt forest understorey and investigated the role of vegetation in mediating these effects using path analysis. Fire had strong negative effects on the density of web-building spiders, which were partly mediated by effects on vegetation structure, while negative effects of large herbivores on web density were not related to changes in vegetation. Fire amplified the effects of large herbivores on spiders, both via vegetation-mediated pathways and by increasing herbivore activity. The importance of vegetation-mediated pathways and fire-herbivore interactions differed for web density and richness and also differed between web types. Our results demonstrate that for some groups of web-building spiders, the effects of co-occurring disturbance drivers may be mostly additive, whereas for other groups, interactions between drivers can amplify disturbance effects. In our study system, the use of prescribed fire in the presence of high densities of herbivores could lead to reduced densities and altered composition of web-building spiders, with potential cascading effects through the arthropod food web. Our study highlights the importance of considering both the independent and interactive effects of disturbances, as well as the mechanisms driving their effects, in the management of disturbance regimes.
干扰格局的改变是全球生物多样性丧失的主要驱动因素。因此，维持或重建自然干扰格局是许多保护计划的重点。然而，一个关键挑战是了解同时发生的干扰如何相互作用以影响生物多样性。我们通过实验测试了规定火烧和大型有袋食草动物对桉树林下层结网蜘蛛群落的交互作用，并使用路径分析研究了植被在介导这些影响中的作用。火烧对结网蜘蛛的密度有强烈的负面影响，部分是通过对植被结构的影响介导的，而大型食草动物对蛛网密度的负面影响与植被变化无关。火烧通过植被介导的途径以及增加食草动物的活动，放大了大型食草动物对蜘蛛的影响。植被介导的途径和火烧与食草动物的相互作用对蛛网密度和丰富度的重要性不同，在不同类型的蛛网之间也有所不同。我们的结果表明，对于某些结网蜘蛛群体，同时发生的干扰驱动因素的影响可能主要是累加的，而对于其他群体，驱动因素之间的相互作用可以放大干扰效应。在我们的研究系统中，在食草动物高密度存在的情况下使用规定火烧可能会导致结网蜘蛛的密度降低和组成改变，并通过节肢动物食物网产生潜在的级联效应。我们的研究强调了在干扰格局管理中考虑干扰的独立和交互作用以及驱动其影响的机制的重要性。
