Identification and Management of Multiple Threats to Rare and Endangered Plant Species
RC-1542, SERDP and ESTCP
Dr. Bernd Blossey, Cornell University
Density and species composition of monitored stressor organisms (earthworms, slugs, and B. pellucidus) varied across field sites and years. Unexpectedly, it was found that earthworm density and biomass decreased in the fenced plots, indicating a possible, but unforeseen, interaction between earthworms and deer. In just five years, it was found that all three target non-native plants had significantly lower abundance (frequency, cover, and/or density) in fenced plots, in response to deer exclusion. This is particularly true for the short-lived M. vimineum and A. petiolata, which are annual and biennial, respectively. Simultaneously, native vegetation responded positively to deer exclusion. Results indicate that it may be possible to reduce abundance of non-native plants simply by substantially reducing deer density.
A demographic study of deer browsing impacts on Trillium grandiflorum
Plant Ecology, May 2003
Thomas P. Rooney and Kevin Gross
A moderate drought during the study could account for the negative population growth rate, but deer browsing accelerates the rate of decline. Population growth is most sensitive to the proportion of plants remaining in the nonflowering stage, and deer browsing reduces this proportion. Browsing damage was relatively low in this study (5.4% of stems in 1998, 11.5% in 1999) compared to another study of browsing impacts on T. grandiflorum, indicating deer could have far more severe demographic consequences in populations subject to higher levels of browsing.
Height of White-Flowered Trillium (Trillium Grandiflorum) as an Index of Deer Browsing Intensity
Roger C. Anderson
Feb 1, 1994
Trillium stem height was positively correlated with reproductive output by perennial herbaceous plants and negatively correlated with the percent of the herbaceous understory that is browsed. This indicates change in stem height is as indication of the general status of the herbaceous flora as influenced by deer browsing. Based on deer population densities associated with study sites supporting Trillium populations with stable stem heights and flowering plants, maintenance of deer densities of 4—6 individuals/km2 is recommended for deciduous forests in northeastern Illinois.