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The Effect of Emerald Ash Borer (Agrilus Planipennis)-Caused Ash Mortality and White-Tailed Deer Abundance on Understory Invasive Shrubs and Forest Regeneration

Hoven, Brian Michael
http://orcid.org/0000-0002-4999-6393
http://rave.ohiolink.edu/etdc/view?acc_num=miami1627656584529987

Abstract Details

2021, Doctor of Philosophy, Miami University, Ecology, Evolution and Environmental Biology.
Invasive insects and shrubs are major threats to North American forests. Emerald ash borer (Agrilus planipennis) (EAB) kills ash trees (Fraxinus spp.) resulting in canopy gaps altering resource availability. Invasive shrubs likely benefit from EAB and suppress tree seedlings. I investigated the response of woody plants to EAB-caused ash mortality in each forest strata at 24 sites throughout western and central Ohio, with particular focus on the seedling layer and introduced shrubs. In 16 sites, I explored the effects of EAB-caused canopy gaps on the invasive shrub Amur honeysuckle (Lonicera maackii) and the effects of L. maackii on woody seedlings. I found a positive relationship between ash decline and L. maackii basal area (BA) growth. Lower seedling richness corresponded with greater L. maackii BA and better ash condition. Greater L. maackii BA was associated with lower seedling abundance and recruitment. In all 24 sites, I tested two mechanisms for ecological response to EAB-caused ash mortality a: (1) EAB-caused ash decline releases growth of upper forest layers (non-ash canopy and subcanopy trees), suppressing lower strata; (2) EAB-caused ash decline increases canopy openness, releasing lower strata (shrub and seedling layer). I found evidence to support both mechanisms. Greater relative growth rates of canopy maple (Acer spp.) occurred in sites with more poor condition ash. More introduced seedlings were present in sites with more ash mortality and shrub cover. I tested the relative importance, additive, and interactive effects of EAB, non-native shrubs, and white-tailed deer (Odocoileus virginianus) on woody seedlings in the context of two environmental factors, canopy tree BA and site wetness. Results indicated a negative effect in drier forests of non-native shrubs on native seedling abundance, richness, and diversity. Deer herbivory reduced seedling diversity, especially in wetter forests. Canopy BA had a positive effect on seedling diversity in drier forests. Ordination analysis revealed site wetness, non-native shrubs and canopy BA were most important in shaping seedling community composition. These results indicate species best adapted to ephemeral resource fluctuations, specifically maple and introduced shrubs and seedlings, benefit most from EAB-caused ash mortality. Additionally, chronic stressors like deer and introduced shrubs such as L. maackii are more important than EAB for shaping future forest composition by shifting seedling communities toward reduced native richness and diversity.
David Gorchov (Advisor)
Thomas Crist (Committee Member)
Hank Stevens (Committee Member)
Nik Money (Committee Member)
Kathleen Knight (Committee Member)
Amélie Davis (Other)
171 p.
Biology; Botany; Ecology; Forestry
Tree fall gap, Facilitation, Fraxinus, Agrilus planipennis, Lonicera maackii, Seedling Recruitment, Chronosequence, Shade Tolerance, Introduced Seedlings, Invasion, diversity, Waterlogging tolerance, Sugar maple browse index, Bray-Curtis ordination

Recommended Citations

Citations

  • Hoven, B. M. (2021). The Effect of Emerald Ash Borer (Agrilus Planipennis)-Caused Ash Mortality and White-Tailed Deer Abundance on Understory Invasive Shrubs and Forest Regeneration [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1627656584529987

    APA Style (7th edition)

  • Hoven, Brian. The Effect of Emerald Ash Borer (Agrilus Planipennis)-Caused Ash Mortality and White-Tailed Deer Abundance on Understory Invasive Shrubs and Forest Regeneration. 2021. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1627656584529987.

    MLA Style (8th edition)

  • Hoven, Brian. "The Effect of Emerald Ash Borer (Agrilus Planipennis)-Caused Ash Mortality and White-Tailed Deer Abundance on Understory Invasive Shrubs and Forest Regeneration." Doctoral dissertation, Miami University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1627656584529987

    Chicago Manual of Style (17th edition)

miami1627656584529987
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© 2021, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.
Release 3.2.12