Ten Facts about Garry Oaks

5 June 2014 by Christopher Buddle, posted in Biodiversity, Plants, Ten facts

This post is written by Carly Ziter, an ecologist, science blogger, and all around amazing person. She's currently in-between her MSc and PhD. I'm super-excited to see a tree featured in the ten fact series: here's some great information about Garry Oaks:

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As a more systems-focused ecologist, I rarely focus on a single organism in my research, but the forest lover in me couldn’t help but feel that the “ten facts” series needed to, shall we say, branch out a little. During my undergraduate degree at the University of Guelph, I had the opportunity to spend two summers working with Dr. Andrew MacDougall’s lab at their field site at the Nature Conservancy of Canada’s Cowichan Garry Oak Preserve (GCOP), on beautiful Vancouver Island, Canada. Located in Maple Bay, BC, the CGOP is one of the world’s best remaining examples of a Garry Oak ecosystem. My primary role there was working on my honours thesis on top-down and bottom-up controls on grassland root dynamics and soil carbon, as well as pitching in as an all around field hand. However, during my stay at the CGOP I absolutely fell in love with the Garry Oak trees the site was named for. Luckily, both Andrew and site manager Irvin Banman were a wealth of knowledge about these trees, and I managed to absorb a fact or two (or, well, ten!) about them during my time there.

1)    “Garry oak” – not to be confused with the popular Pokemon character “Gary Oak” – is a uniquely Canadian moniker for Quercus garryana, a member of the Beech family (family Fagaceae) named for former deputy governor of the Hudson’s Bay Company, Nicholas Garry. For our readers south of the border, this species is commonly referred to as the Oregon White oak.

2)    The Garry oak is the only native oak species that occurs in Western Canada (west of Manitoba), as well as in the state of Washington. In Canada, Garry oak ecosystems currently exist only in British Columbia, primarily occurring on Vancouver Island. The full species range occurs along the pacific coast of North America, from southern British Columbia (lat 49° N) to southern California (lat 34° N).

3)    The Garry oak is a very slow growing tree, reaching approximately 20m (occasionally up to 30m) in height, and typically growing in open woodlands and meadows. Although straight-stemmed stands of Garry oak do occur, the tree more often takes on a characteristic gnarled and twisted, moss-covered form.

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4)    If these gnarled trees look eerily familiar, perhaps it’s because they were the inspiration for the enchanted forest in Disney’s Snow White! Legend has it that Walt Disney was fascinated by the trees’ twisted forms on a tour of southern British Columbia, and incorporated them into his movie.

5)    Can’t see the ecosystem for the trees? Garry oak trees are individually beautiful, attention grabbing organisms, but are really emblematic of an entire ecosystem. Garry oak woodlands and meadows are renowned for their beautiful spring wildflowers (e.g. camas, western buttercups, chocolate lilies), and support the highest diversity of plant species of any terrestrial ecosystem in coastal BC.

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6)    I couldn’t possibly have a “10 facts” without including any 6-legged critters, so for all of our arthropod-minded readers, Garry oak ecosystems are important havens not just for plants, but also for insects! An estimated eight hundred insect and mite species are directly associated with the Garry oak tree (If you’re curious, here’s an annotated list, albeit from several years ago!).

7)    Unfortunately for the myriad plant and animal species associated with the Garry oak, Garry oak meadows are among the most endangered ecosystems in Canada – less than 5% of British Columbian Garry oak habitat remains intact (and less than 10% worldwide). Approximately 100 species at risk are affiliated with Garry oak ecosystems.

8)    If you were to drive through southern BC, you would likely notice several mature Garry oak trees, but a surprising lack of young recruits. Many Garry Oak seedlings are damaged or killed via herbivory by (primarily exotic) small mammals. This competition with exotic animal species is occurring in combination with encroachment of exotic grasses and shrubs, rapid land development and increased habitat fragmentation/degradation, and woody encroachment due to fire suppression. Sadly, this cocktail of threats to both young and established trees paints a bleak picture for the future of the Garry oak. Fortunately, there are conservation groups dedicated to the recovery of this species and its habitat.

9)    Garry oak ecosystems are not “natural”, but rather have a long history of human management. In contrast to today’s fire suppression, in the past, the Coast Salish First Nations peoples deliberately burned Garry oak meadows and woodlands to promote the growth of the camas flower – the bulbs of which were cultivated as an important food source. Now, many Garry oak stands are out-competed by Douglas-fir trees, which shade out the oaks, leading to the conversion of oak meadows to conifer forests.

10)    Landscapes of the future? Garry oak is well adapted to a Mediterranean climate, characterized by warm temperatures with extended summer drought. These sites often occur at the margins of higher productivity forests, where drought conditions prevent other species from flourishing. If climate change brings drier and warmer conditions, the Garry oak tree may expand its range – however, whether the unique understory community will expand with the tree is less certain, as invasive species become increasingly prevalent.

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