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Woody seedling community responses to deer herbivory, introduced shrubs, and ash mortality depend on canopy competition and site wetness

Formally Refereed

Abstract

Emerald ash borer (EAB) (Agrilus planipennis), non-native shrubs, and white-tailed deer (Odocoileus virginianus) have been independently shown to affect woody seedling communities. Our objective was to determine the relative importance as well as additive and interactive-effects of these stressors in the context of two environmental factors, canopy tree competition and site wetness. We sampled 24 sites, representing three natural noncongruent gradients in ash mortality, deer browse, and introduced shrub invasion. We explored the responses of seedling species abundance, diversity and richness to an array of deer herbivory, ash mortality, and introduced shrubs and varying levels of canopy tree competition, site wetness. The effects of each stressor on the differences in the relative abundance of seedling species was also evaluated. Our results indicate a persistent negative effect of non-native shrubs in drier forest plots on native seedling abundance, richness, and diversity. In wetter forests, non-native shrubs had no effect on native seedling richness or abundance and were positively related to diversity. Deer browse had a negative effect on seedling diversity in wetter forests and no effect in drier forests. Canopy tree competition had a positive effect on seedling diversity in drier forest plots, but negatively affected diversity in wetter forest plots. Ordination analysis revealed that site wetness, non-native shrubs and the total basal area of trees in the stand had the largest impacts on the species composition of seedlings found at each site. Our results suggest that site wetness and chronic stressors like deer and introduced shrubs are interacting to shift seedling communities towards fewer native species as well as to reduce seedling species richness and diversity.

Keywords

Fraxinus, Emerald ash borer, Agrilus planipennis, Seedling diversity, Waterlogging tolerance, Sugar maple browse index, Bray-Curtis ordination, White-tailed deer, Odocoileus virginianus

Citation

Hoven, Brian M.; Knight, Kathleen S.; Peters, Valerie E.; Gorchov, David L. 2022. Woody seedling community responses to deer herbivory, introduced shrubs, and ash mortality depend on canopy competition and site wetness. Forest Ecology and Management. 523(8): 120488. 14 p. https://doi.org/10.1016/j.foreco.2022.120488.
Citations
https://www.fs.usda.gov/research/treesearch/65190