Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, SL5 7PY, U.K.
Conserv Biol. 2020 Aug;34(4):977-987. doi: 10.1111/cobi.13438. Epub 2020 Jun 27.
The cascading effects of biodiversity loss on ecosystem functioning of forests have become more apparent. However, how edge effects shape these processes has yet to be established. We assessed how edge effects alter arthropod populations and the strength of any resultant trophic cascades on herbivory rate in tropical forests of Brazil. We established 7 paired forest edge and interior sites. Each site had a vertebrate-exclosure, procedural (exclosure framework with open walls), and control plot (total 42 plots). Forest patches were surrounded by pasture. Understory arthropods and leaf damage were sampled every 4 weeks for 11 months. We used path analysis to determine the strength of trophic cascades in the interior and edge sites. In forest interior exclosures, abundance of predaceous and herbivorous arthropods increased by 326% and 180%, respectively, compared with control plots, and there were significant cascading effects on herbivory. Edge-dwelling invertebrates responded weakly to exclusion and there was no evidence of trophic cascade. Our results suggest that the vertebrate community at forest edges controls invertebrate densities to a lesser extent than it does in the interior. Edge areas can support vertebrate communities with a smaller contingent of insectivores. This allows arthropods to flourish and indirectly accounts for higher levels of plant damage at these sites. Increased herbivory rates may have important consequences for floristic community composition and primary productivity, as well as cascading effects on nutrient cycling. By interspersing natural forest patches with agroforests, instead of pasture, abiotic edge effects can be softened and prevented from penetrating deep into the forest. This would ensure a greater proportion of forest remains habitable for sensitive species and could help retain ecosystem functions in edge zones.
生物多样性丧失对森林生态系统功能的级联效应变得更加明显。然而，边缘效应对这些过程的影响尚未确定。我们评估了边缘效应对节肢动物种群的影响，以及这些过程对巴西热带森林中食草率的任何潜在营养级联的强度。我们建立了 7 对森林边缘和内部的地点。每个地点都有一个脊椎动物围栏、程序围栏（带有开口墙的围栏框架）和对照区（共 42 个区）。森林斑块被牧场包围。在 11 个月的时间里，每隔 4 周就会对下层植被的节肢动物和叶片损伤进行采样。我们使用路径分析来确定内部和边缘站点中营养级联的强度。在森林内部的围栏内，与对照区相比，捕食性和食草性节肢动物的丰度分别增加了 326%和 180%，并且对食草性有明显的级联效应。边缘栖息的无脊椎动物对排除的反应较弱，没有证据表明存在营养级联。我们的结果表明，与内部相比，森林边缘的脊椎动物群落对无脊椎动物密度的控制程度较小。边缘地区可以支持脊椎动物群落，其中昆虫捕食者的数量较少。这使得节肢动物得以繁荣，间接导致这些地点的植物损伤程度更高。食草率的增加可能对植物群落组成和初级生产力以及养分循环的级联效应产生重要影响。通过在农田中散布天然森林斑块，而不是牧场，可以软化非生物边缘效应，并防止其深入森林。这将确保更大比例的森林对敏感物种仍然适宜，并有助于在边缘区保留生态系统功能。
