title: Insect herbivores increase mortality and reduce tree seedling growth of some species in temperate forest canopy gaps.
abstract: Insect herbivores help maintain forest diversity through selective predation on seedlings of vulnerable tree species. Although the role of natural enemies has been well-studied in tropical systems, relatively few studies have experimentally manipulated insect abundance in temperate forests and tracked impacts over multiple years. We conducted a three-year experiment (2012-2014) deterring insect herbivores from seedlings in new treefall gaps in deciduous hardwood forests in Maryland. During this study, we tracked recruitment of all tree seedlings, as well as survivorship and growth of 889 individual seedlings from five tree species:Acer rubrum,Fagus grandifolia,Fraxinusspp.,Liriodendron tulipifera, andLiquidambar styraciflua. Insect herbivores had little effect on recruitment of any tree species, although there was a weak indication that recruitment ofA. rubrumwas higher in the presence of herbivores. Insect herbivores reduced survivorship ofL. tulipifera, but had no significant effects onA. rubrum,Fraxinusspp.,F. grandifolia, orL. styraciflua. Additionally, insects reduced growth rates of early pioneer speciesA. rubrum,L. tulipifera, andL. styraciflua, but had little effect on more shade-tolerant speciesF. grandifoliaandFraxinusspp. Overall, by negatively impacting growth and survivorship of early pioneer species, forest insects may play an important but relatively cryptic role in forest gap dynamics, with potentially interesting impacts on the overall maintenance of diversity.
authors.affiliation: Department of Biology, Colorado State University , Fort Collins , CO , United States.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Lemoine
authors.affiliation: Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara , CA , United States.
authors.forename: Deron E
authors.initials: DE
authors.lastname: Burkepile
authors.affiliation: Smithsonian Environmental Research Center , Edgewater , MD , United States.
authors.forename: John D
authors.initials: JD
authors.lastname: Parker
keywords: Bayesian hierarchical model; Herbivory; Recruitment; Succession; Treefall gaps