Department of Natural Resource Sciences, McGill University , Ste-Anne-de-Bellevue, Quebec , Canada.
PeerJ. 2013 Aug 22;1:e138. doi: 10.7717/peerj.138. eCollection 2013.
The forest canopy offers a vertical gradient across which variation in predation pressure implies variation in refuge quality for arthropods. Direct and indirect experimental approaches were combined to assess whether canopy strata differ in ability to offer refuge to various arthropod groups. Vertical heterogeneity in impact of avian predators was quantified using exclosure cages in the understory, lower, mid, and upper canopy of a north-temperate deciduous forest near Montreal, Quebec. Bait trials were completed in the same strata to investigate the effects of invertebrate predators. Exclusion of birds yielded higher arthropod densities across all strata, although treatment effects were small for some taxa. Observed gradients in predation pressure were similar for both birds and invertebrate predators; the highest predation pressure was observed in the understory and decreased with height. Our findings support a view of the forest canopy that is heterogeneous with respect to arthropod refuge from natural enemies.
森林冠层提供了一个垂直梯度，在这个梯度上，捕食压力的变化意味着节肢动物的避难所质量也在变化。本研究结合了直接和间接的实验方法，以评估不同的冠层层是否在为各种节肢动物群体提供避难所的能力上存在差异。在魁北克省蒙特利尔附近的北温带落叶林的林下层、下层、中层和上层冠层中使用围栏来量化鸟类捕食者的垂直异质性。在相同的层中完成了诱饵试验，以研究无脊椎动物捕食者的影响。鸟类的排除导致所有层的节肢动物密度都升高，尽管对某些分类群的处理效果很小。鸟类和无脊椎动物捕食者的捕食压力梯度相似；在林下层观察到的捕食压力最高，随着高度的增加而降低。我们的研究结果支持了一种观点，即森林冠层在节肢动物躲避天敌方面是具有异质性的。
