Remnant population of bur oaks in southwestern Nebraska
Quercus macrocarpa). Nevertheless, the Bur Oak Canyon in southern Hitchcock County, Nebraska, has sheltered a remnant bur oak population for thousands of years.
The stand of oaks in Bur Oak Canyon is believed to date back 5,000 to 10,000 years. Of the 300 to 400 bur oaks in the canyon today, some individuals may be 200 years old. They are the only known native bur oaks within 200 miles.
Forester Tim Buchanan of Fort Collins, Colorado, explains that after the last ice age ended about10,000 years ago, the climate became favorable for oaks to spread across the prairies. Oaks advanced even into some parts of Canada. Then about 5000 years ago, the climate became hot and dry on the Great Plains -- and in the area of the Bur Oak Canyon. Oak trees on the surrounding prairies died from the stress of prolonged drought.
The microclimate and geology of the deep canyon helped the bur oaks survive. The bur oak's long taproot also gave the tree a survival advantage. A bur oak seedling sends its taproot deep into the ground before it begins to add height above ground. In the first growing season, it may develop a taproot over a yard in length. It also develops an extensive system of lateral and feeder roots.
It is suspected that the bur oaks in the canyon carry some genes from hybridizing long ago with other oaks, probably with gambel oaks (Quercus gambelii) and post oaks (Quercus stellata). Gambel oaks are native to South Dakota, Colorado, and the American Southwest. Post oaks are native to most of the Eastern United States. Neither post oaks nor gambel oaks are native to Nebraska today -- presumably they died out in the great drought 5000 years ago, if they ever grew in the area.
Due to cattle grazing in the canyon (which is privately owned and part of a ranch) and a lack of squirrels to disperse the seed, seedlings have a hard time getting started.
The activities of the 2009 Bur Oak Symposium include planting seedlings and acorns, and protecting new and established seedlings. The goal is to reestablish and preserve the stand of oaks in Bur Oak Canyon for the future.
More about Bur Oak Canyon:
Bur Oak Symposium 2008
Bur Oak Symposium 2009
Bur Oak Canyon -- Flickr photoset
Bur Oak Canyon -- Flickriver photoset
Bur Oaks Grown from Seed -- Flickriver photoset
Images in this post are from Wikipedia.