Download effects of anthropogenic disturbance on habitat and life history

CONSERVATION OF THE ENDANGERED LIMESTONE ENDEMIC SALIX
JEJUNA; EFFECTS OF ANTHROPOGENIC DISTURBANCE
ON HABITAT AND LIFE HISTORY
by
© Julie L Robinson
A thesis submitted to the School of Graduate Studies
in partial fulfilment of the requirements for the
degree of Master of Science.
Department of Biology
Memorial University
May 2010
St. John’s
Newfoundland
Abstract
Anthropogenic disturbance has been shown to have negative impacts on the
recovery of endangered or rare species. Specific recovery objectives for Salix
jejuna, an endangered prostrate shrub endemic to the globally rare limestone
barrens habitat of Newfoundland (Canada), include assessing the population
dynamics of natural populations, understanding limiting factors, defining threats
and mitigating controllable threats where possible. As a large portion of
S. jejuna’s habitat has been anthropogenically-disturbed, understanding the
effects of disturbance on species persistence are central to promoting species
recovery.
An assessment of habitat features revealed that anthropogenicallydisturbed substrates were more homogeneous than undisturbed, natural
substrates, with more gravel, less exposed bedrock, decreased soil moisture, and
increased nutrient content. Populations resident on anthropogenically-disturbed
habitats tended towards a more “annual” dynamic, with a greater proportion of
seedlings, lower levels of clonal growth, and a younger median age compared
with populations on naturally-disturbed substrates. Therefore, specific recovery
plans for S. jejuna should include the elimination of continual disturbances such
as off-road vehicle use and the active restoration of disturbed habitat to restore
natural ecosystem processes, to reflect adjacent undisturbed natural habitat, and
to promote the clonal reproductive traits of natural populations.
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