Synergistic effects of wild ungulates and management intensification suppress native plants and promote exotics - Dataset Public Deposited

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  • This dataset consists of native and exotic plant species metrics, including cover, richness, relative abundance and responses to the exclusion of wild ungulates and herbivory. The data were used for the manuscript: "Synergistic effects of wild ungulates and management intensification suppress native plants and promote exotics", published in the journal Forest Ecology and Management. We used mixed-effects models in the R Statistical Package to test the interactive effects of herbicide and herbivory on native and exotic species for six years following timber harvest.
  • MANUSCRIPT ABSTRACT In managed forest landscapes, conflicts among wood production, ungulates, native biodiversity, and exotic species are common. As humanity allocates more land as intensively managed plantations, these conflicts may become more severe. For instance, native ungulates have been implicated in the loss of native plant diversity, declines in timber revenues and the spread of exotic species in many forest systems, yet the synergistic effects of management and ungulate herbivory are not well understood. We hypothesized that herbicide and herbivore-induced suppression of native forage species promotes the release of exotic species in young forest plantations. Further, we expected herbivory and the retention of native forage via less intensive management would have negative consequences for reforestation objectives. To test this hypothesis, we conducted an experiment that manipulated management intensity (via herbicides) and access of two deer species to vegetation (via exclosures) on 28 operational Douglas-fir plantations of the Pacific Northwest, USA. We recorded yearly plant species cover estimates and tested the effects of herbivory and herbicides on native and exotic plants during the first six years of plantation establishment. Heavier herbicide treatments reduced the cover and diversity of native plants, and increased the cover of exotics over time, particularly that of exotic herbaceous species. Regardless of herbicide intensity, herbivores had reduced the cover of native forage species. In a treatment that represents operational standards applied to over 2.5 million ha in the region, the suppression of native species by deer corresponded with an increase in exotic species cover by 23 percent, resulting in equitable abundance of native and exotic plants. As expected, Douglas-fir growth was suppressed when herbivores were present and vegetation was left untreated by herbicides, although the presence of deer promoted both crop-tree growth and the relative abundance of exotics in our most intensive treatment, presumably due to the added suppression of native competitors. Our findings suggest that wild ungulates amplify management-driven shifts toward exotic species in intensively managed forest plantations. Exotic plant forage status and adaptations to frequent disturbance seem to be key mechanisms for the synergistic effects we observed. Without herbicides, diverse assemblages of native species are buffered from herbivory and exotic species proliferation, with potential tradeoffs for timber production. Our results highlight the role of management intensity in modifying the interactions among exotic plants and native herbivores, contributing to a mechanistic understanding of the role of native biodiversity in regulating exotic species spread. Our data provide further support for growing evidence that synergistic effects of multiple drivers can facilitate exotic proliferation.
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  • Stokely, T. D. (2019) Synergistic effects of wild ungulates and management intensification suppress native plants and promote exotics - Dataset (Version 1) [Dataset]. Oregon State University.
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  • Funding was provided by the United States Department of Agriculture, Agriculture and Food Research Initiative grant (AFRI-2009-04457, AFRI-2015-67019-23178), the National Council for Air and Stream Improvement, Inc., the Oregon Forest Industries Council, and the Oregon State University College of Forestry (Giustina Family Research grant, Noble fund, Fish and Wildlife Habitat in Managed Forests grant, Dean’s fund and Institute for Working Forest Landscapes).
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  • These data were used in the analysis for the manuscript titled: "Deer-mediated ecosystem service vs. disservice depends on forest management intensity", published in the Journal of Applied Ecology.



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