| Garry Oak | |
|---|---|
| Mature Garry Oak | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Rosids |
| Order: | Fagales |
| Family: | Fagaceae |
| Genus: | Quercus |
| Section: | Quercus |
| Species: | Q. garryana |
| Binomial name | |
| Quercus garryana Douglas ex Hook. |
|
Quercus garryana, the Garry Oak, Oregon White Oak or Oregon Oak, has a range from southern California to extreme southwestern British Columbia, particularly southeastern Vancouver Island and the adjacent Gulf Islands. It grows from sea level to 210 m altitude in the northern part of its range, and at 300-1800 m in the south of the range in California. The tree is named after Nicholas Garry, deputy governor of the Hudson's Bay Company, 1822-35.[1]
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In British Columbia, the Garry oak occurs on the Gulf Islands and southeastern Vancouver Island, from west of Victoria along the east side of the island up to the Campbell River area. There are also small populations along the Fraser River on the British Columbia mainland.[1]
In Washington State, it grows on the west side of the Cascade Mountains, particularly in the Puget Sound lowlands, the northeastern Olympic Peninsula, Whidbey Island and the San Juan Islands. It also grows in the foothills of the southeastern Cascade Mountains and along the Columbia River Gorge.[2][3]
In Oregon, the Garry oak grows on the west side of the Cascade Mountains, primarily in the Willamette, Umpqua and Rogue River Valleys, and along the Columbia River Gorge.[2][3]
In California, the garryana variety grows in the foothills of the Siskiyou and Klamath Mountains, the Coast Ranges of Northern California, and of the west slope of the Cascade Mountains. The semota variety grows in the Sierra Nevada and Coast Ranges as far south as Los Angeles County.[4]
There are three varieties:
It is a drought-tolerant tree, typically of medium height, growing slowly to around 20m (occasionally as high as 30m) or as a shrub to 3-5 m tall. It has the characteristic oval profile of other oaks when solitary, but is also known to grow in groves close enough together that crowns may form a canopy. The leaves are deciduous, 5-15 cm long and 2-8 cm broad, with 3-7 deep lobes on each side. The flowers are catkins, the fruit a small acorn 2-3 cm (rarely 4 cm) long and 1.5-2 cm broad, with shallow, scaly cups.
The Oregon White Oak is commonly found in the Willamette Valley hosting the mistletoe Phoradendron flavescens. It is also commonly found hosting galls created by wasps in the family Cynipidae. 'Oak apples', green or yellow ball of up to 5 cm in size, are the most spectacular.[5] They are attached to the undersides of leaves. One common species responsible for these galls is Cynips maculipennis. Other species create galls on stems and leaves. Shapes vary from spheres to mushroom-shaped to pencil-shaped.
In British Columbia, the Garry oak can be infested by three nonnative insects: the jumping gall wasp Neuroterus saltatorius, the oak leaf phylloxeran, and the gypsy moth.[1]
While the invasive plant disease commonly called Sudden Oak Death attacks other Pacific Coast native oaks, it has not yet been found on the Garry oak. Most oak hosts of this disease are in the red oak group, while Garry oak is in the white oak group.[6]
Garry oak is the only native oak species in British Columbia, Washington State, and northern Oregon. In these areas, Garry oak woodlands are seral, or early-successional - they depend on disturbance to prevent their being overtaken by Douglas-fir. The disturbance that allowed Garry oak to persist in an area that would otherwise succeed to coniferous forest was primarily fire. Natural wildfires are rare in the maritime Pacific Northwest, but early settler's records, soil surveys, and tribal histories indicate that deliberate burning was widely practiced by the First Nations people of these areas. Fire perpetuated the grasslands that produced food plants such as camas, chocolate lily, bracken fern, and oak; and that provided grazing and easy hunting for deer and elk. Mature Garry oaks are fire resistant, so would not be harmed by frequent, light intensity, grass fires. These fires prevented Douglas-fir, and most other conifer, seedlings from becoming established, allowing bunch grass prairie and Garry oak woodland to persist in a high-rainfall area otherwise dominated by conifers. Fire also kept oak woodlands on drier soils free of a shrub understory. Wetter oak woodlands historically had a substantial shrub understory, primarily snowberry. (Perdue IN Dunn and Ewing).[7]
Garry oak woodlands in British Columbia and Washington state are critical habitats for a number of species that are rare or extirpated in these areas, plant, animal, and bryophyte:
(Hanna and Dunn IN Dunn and Ewing;[7] T. Lea, Miles and McIntosh, GOERT Colloquium 2006).
Garry oak woodlands create a landscape mosaic of grassland, savanna, woodland, and closed-canopy forest. This mosaic of varied habitats, in turn, allows many more species to live in this area than would be possible in coniferous forest alone. Parks Canada states that Garry oak woodlands support more species of plants than any other terrestrial ecosystem in British Columbia.[8] It grows in a variety of soil types, for instance, rocky outcrops, glacial gravelly outwash, deep grassland soils, and seasonally flooded riparian areas. (Hanna and Dunn IN Dunn and Ewing;[7] T. Lea, GOERT Colloquium 2006).
The Donation Land Claim Act of 1850 encouraged Anglo settlement of Washington and Oregon, and marked the beginning of the end of regular burning by Indians of the area (Perdue IN Dunn and Ewing).[7] With fire suppression and conversion to agriculture, Garry oak woodlands and bunch grass prairies were invaded by Douglas-fir, Oregon ash (Fraxinus latifolia}, and imported pasture grasses. Oaks were logged to clear land for pasture, and for firewood and fence posts. Livestock grazing trampled and consumed oak seedlings. By the 1990s, more than half the Garry oak woodland habitat in the South Puget Sound area of Washington State was gone. (Hanna and Dunn IN Dunn and Ewing.[7] On Vancouver Island , more than 90% was gone. (T. Lea, GOERT Colloquium 2006). Remaining Garry oak woodlands are threatened by urbanization, conversion to Douglas-fir, and invasion by shrubs, both native and nonnative (Scotch broom Cytisus scoparius, sweetbriar rose Rosa eglanteria, snowberry Symphoricarpos albus, Indian plum Oemleria cerasiformis, poison-oak Toxicodendron diversilobum, English holly Ilex aquifolium, bird cherry Prunus avens).[3] Conversely, oak groves in wetter areas that historically had closed canopies of large trees are becoming crowded with young oaks that grow thin and spindly, due to lack of fires that would clear out seedlings.(Hanna and Dunn IN Dunn and Ewing;[7]
Although the wood has a beautiful grain, it is difficult to season without warping and therefore the Garry Oak has not historically been regarded as having any commercial value and is frequently destroyed as land is cleared for development. However, Garry Oaks and their ecosystems are the focus of conservation efforts, including in communities such as Oak Bay, British Columbia, which is named after the tree, and Corvallis, Oregon.[9] Moreover, recently the wood, which is similar to that of other white oaks, has been used experimentally in Oregon for creating casks in which to age wine.