title: Does predation contribute to tree diversity?
abstract: Seed and seedling predation may differentially affect competitively superior tree species to increase the relative recruitment success of poor competitors and contribute to the coexistence of tree species. We examined the effect of seed and seedling predation on the seedling recruitment of three tree species, Acer rubrum (red maple), Liriodendron tulipifera (yellow poplar), and Quercus rubra (northern red oak), over three years by manipulating seed and seedling exposure to predators under contrasting microsite conditions of shrub cover, leaf litter, and overstory canopy. Species rankings of seedling emergence were constant across microsites, regardless of exposure to seed predators, but varied across years. A. rubrum had the highest emergence probabilities across microsites in 1997, but Q. rubra had the highest emergence probabilities in 1999. Predators decreased seedling survival uniformly across species, but did not affect relative growth rates (RGRs). Q. rubra had the highest seedling survivorship across microsites, while L. tulipifera had the highest RGRs. Our results suggest that annual variability in recruitment success contributes more to seedling diversity than differential predation across microsites. We synthesized our results from separate seedling emergence and survival experiments to project seedling bank composition. With equal fecundity assumed across species, Q. rubra dominated the seedling bank, capturing 90% of the regeneration sites on average, followed by A. rubrum (8% of sites) and L. tulipifera (2% of sites). When seed abundance was weighted by species-specific fecundity, seedling bank composition was more diverse; L. tulipifera captured 62% of the regeneration sites, followed by A. rubrum (21% of sites) and Q. rubra (17% of sites). Tradeoffs between seedling performance and fecundity may promote the diversity of seedling regeneration by increasing the probability of inferior competitors capturing regeneration sites.
authors.affiliation: Department of Botany, University of Vermont, Marsh Life Science Building, Burlington, VT 05405, USA. Brian.Beckage@uvm.edu
authors.forename: Brian
authors.initials: B
authors.lastname: Beckage
authors.forename: James S
authors.initials: JS
authors.lastname: Clark
mesh_terms: D017753:Ecosystem; D004777:Environment; D005298:Fertility / Q000502:physiology; D020387:Food Chain; D016014:Linear Models; D009657:North Carolina; D012639:Seeds / Q000254:growth & development*; D013045:Species Specificity; D014197:Trees / Q000254:growth & development / Q000502:physiology*
references.citation: Nature. 2002 May 23;417(6887):437-40
references.pmid: 12024212
references.citation: Am Nat. 1992 Aug;140(2):243-60
references.pmid: 19426058
references.citation: Science. 2004 Jul 30;305(5684):663-5
references.pmid: 15286371
references.citation: Oecologia. 2001 Apr;127(2):281-286
references.pmid: 24577661
references.citation: Oecologia. 1979 Dec;44(1):141-142
references.pmid: 28310478
references.citation: Am J Bot. 1998 Jan;85(1):79
references.pmid: 21684882
references.citation: Am Nat. 1992 Aug;140(2):261-86
references.pmid: 19426059
references.citation: Oecologia. 1985 Aug;67(1):150-153
references.pmid: 28309862