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Davidsonia 17:3 87
Comparison of Two Garry Oak Sites
Undergoing Restoration on Southeastern
Vancouver Island: a Preliminary Study
ABSTRACT
Garry oak ecosystems represent unique species-rich communities in the Pacific
Northwest United States and southwestern Canada. These distinct ecosystems
are becoming rare as their integrity is threatened by urban and agricultural encroachments,
as well as by the introduction of non-native plant taxa. We visited
two Garry oak parklands, one that had been heavily impacted until recently
by grazing cattle, and one that has been protected from such anthropogenic
activities for several years and currently has an active restoration program.
We compared the quantitative occurrence and compositional variation of six
regionally common plant species between these two sites using univariate and
multivariate statistical methods. Our results showed clear differences in the
quantitative patterns of abundance and overall variation among species between
the two sites. These results indicate that the restoration efforts at Site 2 have
promoted greater coverage of native species and greater community variation,
both considered to be positive indicators of biodiversity for this ecosystem.
INTRODUCTION
Garry oak (Quercus garryana) ecosystems occur in the northwestern
United States from the Puget Trough in Washington State, to low
elevations in the Klamath Mountains on the Oregon/California
border (Natureserve, 2006). The Canadian sites that are found along
the southeastern coast of Vancouver Island and throughout the Gulf
Islands, are at the northern limits of the ecosystem (Dunn and Ewing,
1997). These Garry oak communities are thought to be remnants of a
hardwood forest that covered much of the Pacific Northwest between
ice ages. Garry oak communities reached their widest distribution
Heather Esson, Aaron Heiss, Chris Sears* and Nyssa Temmel,
Graduate Students, Department of Botany,
University of British Columbia, Vancouver, BC, V6T 1Z4.
All authors contributed equally.
*Author for correspondence: e-mail: sears@interchange.ubc.ca