Plant Herbivore Interactions at the Forest Edge Rainer Wirth ( ), Sebastian T. Meyer, Inara R. Leal, and Marcelo Tabarelli Contents 1 Introduction .......................................................................................................................... 424 2 What Edges Induce in Forest Remnants............................................................................... 425 3 Plant-Herbivore Interactions at the Edge: Patterns and Processes ....................................... 427 3.1 Patterns ........................................................................................................................ 427 3.2 Processes ..................................................................................................................... 432 4 Impact of Herbivory on the Forest Edge .............................................................................. 436 4.1 Abiotic Conditions ...................................................................................................... 437 4.2 Plant Community......................................................................................................... 438 4.3 Higher Trophic Levels ................................................................................................. 440 5 Conclusions and Outlook ..................................................................................................... 441 References .................................................................................................................................. 442 Abstract An ever-increasing proportion of the global forested landscape is in close proximity to edges and edge effects have been shown to represent key forces affecting both organisms and ecological processes. Despite increasing recognition of edge effects on species interactions, a systematic review devoted to plant- herbivore interactions along forest edges has not yet been performed. Here we syn- thesize published research attempting to detect patterns of herbivore densities and herbivory at forest edges, identify the underlying mechanisms generating these patterns, and explore their potential impacts for the forest edge as an ecosystem. Key conclusions are that herbivores, especially generalists, profoundly benefit from forest edges, often due to favourable microenvironmental conditions, an edge-induced increase in food quantity/quality, and (less well documented) disrupted top-down regulation of herbivores. Finally, we present evidence and causal explanations that edge-associated herbivores, via a range of direct and indirect impacts, may alter species interactions, delay successional processes at the edge, and amplify the often human-induced changes on forest biota. Rainer Wirth Plant Ecology & Systematics, University of Kaiserslautern, PO Box 3049, D-67663 Kaiserslautern, Germany e-mail: wirth@rhrk.uni-kl.de U. Lüttge et al. (eds.), Progress in Botany 69. 423 © Springer-Verlag Berlin Heidelberg 2008