Weak effects of birds, bats and ants on their arthropod prey on pioneering tropical forest gap vegetation

The relative roles of plants competing for resources versus top-down control of vegetation by herbivores, in turn impacted by predators, during early stages of tropical forest succession remain poorly understood. Here we examine the impact of insectivorous birds, bats and ants exclusion on arthropods communities on replicated 5x5 m of pioneering early successional vegetation plots in lowland tropical forest gaps in Papua New Guinea. In plots from which focal taxa of predators were excluded we observed increased biomass of herbivorous and predatory arthropods, and increased density, and decreased diversity of herbivorous insects. However, changes in the biomass of plants, herbivores and arthropod predators were positively correlated or uncorrelated between these three trophic levels and also between individual arthropod orders. Arthropod abundance and biomass correlated strongly with the plant biomass irrespective of the arthropods’ trophic position – a signal of bottom-up control. Patte...

热带森林演替早期阶段，植物间资源竞争的相对作用，与草食动物对植被的自上而下调控效应（该效应又受捕食者影响）这一科学问题，目前仍未得到充分阐释。本研究以巴布亚新几内亚低地热带林隙中经重复布设的5米×5米先锋早期演替植被样地为研究对象，探究食虫鸟类、蝙蝠及蚂蚁的排除处理对节肢动物（arthropods）群落的影响。在排除目标捕食者类群的样地中，我们观测到草食性与捕食性节肢动物的生物量均有所提升，草食性昆虫的密度升高、多样性却出现下降。然而，植物、草食动物与节肢动物捕食者这三个营养级（trophic level）之间，以及各节肢动物类群之间，其生物量的变化要么呈正相关，要么无相关性。无论节肢动物的营养位（trophic position）如何，其丰度与生物量均与植物生物量呈现极强的相关性——这一结果印证了上行调控（bottom-up control）效应。Patte...