title: Ungulate browsers promote herbaceous layer diversity in logged temperate forests.
abstract: Ungulates are leading drivers of plant communities worldwide, with impacts linked to animal density, disturbance and vegetation structure, and site productivity. Many ecosystems have more than one ungulate species; however, few studies have specifically examined the combined effects of two or more species on plant communities. We examined the extent to which two ungulate browsers (moose [Alces americanus]) and white-tailed deer [Odocoileus virginianus]) have additive (compounding) or compensatory (opposing) effects on herbaceous layer composition and diversity, 5-6 years after timber harvest in Massachusetts, USA. We established three combinations of ungulates using two types of fenced exclosures - none (full exclosure), deer (partial exclosure), and deer + moose (control) in six replicated blocks. Species composition diverged among browser treatments, and changes were generally additive. Plant assemblages characteristic of closed canopy forests were less abundant and assemblages characteristic of open/disturbed habitats were more abundant in deer + moose plots compared with ungulate excluded areas. Browsing by deer + moose resulted in greater herbaceous species richness at the plot scale (169 m(2)) and greater woody species richness at the subplot scale (1 m(2)) than ungulate exclusion and deer alone. Browsing by deer + moose resulted in strong changes to the composition, structure, and diversity of forest herbaceous layers, relative to areas free of ungulates and areas browed by white-tailed deer alone. Our results provide evidence that moderate browsing in forest openings can promote both herbaceous and woody plant diversity. These results are consistent with the classic grazing-species richness curve, but have rarely been documented in forests.
authors.affiliation: Highstead PO Box 1097 Redding Connecticut 06875.
authors.forename: Edward K
authors.initials: EK
authors.lastname: Faison
authors.affiliation: U.S. Geological Survey Massachusetts Cooperative Fish & Wildlife Research University of Massachusetts Amherst 160 Holdsworth Way Amherst Massachusetts 01003.
authors.forename: Stephen
authors.initials: S
authors.lastname: DeStefano
authors.affiliation: Harvard Forest Harvard University 324 North Main Street Petersham Massachusetts 01366.
authors.forename: David R
authors.initials: DR
authors.lastname: Foster
authors.affiliation: The Conway School 332 South Deerfield Road Conway Massachusetts 01341.
authors.forename: Glenn
authors.initials: G
authors.lastname: Motzkin
authors.affiliation: Harvard Forest Harvard University 324 North Main Street Petersham Massachusetts 01366.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Rapp
keywords: Browsing; disturbance; herbivory; moose; species richness; white‐tailed deer