Bur Oak - chêne à gros fruits

A tree found in southern Manitoba, usually in dry habitats.

Life Cycle

Bur oaks are slow growing, long-lived trees. Their thick bark, dense hard wood and high tannic content make them resistant to many pathogens. In Manitoba, their estimated lifespan is 200 years; further south bur oak have been recorded living to 400 years.

In Manitoba, the normal height range is between 15 to 20 m (50 to 65 ft) tall) but some are known to grow over 31 m (100 ft). Trees growing in persistently dry habitats may never grow taller than half the normal height. Their short stature in relation to oaks growing in other regions earned them the local name of 'scrub oak'.

Oak seeds or acorns are a valuable food resource for many animals from tiny weevils that bore into the hard shells to deer and black bears. Blue jays and squirrels both collect ripe acorns and hide them to eat later. Some of these hidden food caches remain uneaten and grow into new oak trees. Blue jays have been found to have a significant role in establishing new oaks through this habit.

Habitat

Bur oak is the dominant native tree in Manitoba in moisture zones between that of the aspen forest and the river bottom forest of elm, ash and basswood. It is a deep rooted species that can tolerate intermittent drought. It is not usually found in wet habitats such as marshes, swamps or bogs.

Bur oaks are not able to tolerate much shade and form a minor component in mixed forests of larger trees. Thick stands of oak saplings will develop into oak forests of mature trees spaced so that each tree's canopy touches the the ones surrounding it. Other plants living in such a forest have to make the most of the early spring growing period before the sunlight is blocked by the oak canopy.

Historically, bur oaks grew in scattered stands on the tall grass prairie where their thick corky bark enabled them to survive the occasional prairie fire. Very little of this oak savannah can be still found in Manitoba as agricultural clearing has removed much of the prairie.

Distribution

In Manitoba, bur oaks are found throughout the southern third of the province. The northern edge of its range runs roughly northwest from southeastern Manitoba up to Berens River on the east shore of Lake Winnipeg and then west to the north end of Lake Winnipegosis and the Saskatchewan border. Elsewhere it is found in Canada in Saskatchewan, Ontario, Quebec, and New Brunswick and in the United States primarily in the mid-western states from Montana east to the Atlantic and south to Texas.

Naming and Classification

Bur oak is the only species of oak native to Manitoba - its scientific name is Quercus macrocarpa. Quercus is the genus name that is applied to all oak trees; it is the word the Romans are thought to have used for this type of tree in the Latin language. Macrocarpa is the name applied to this species in 1801 by André Michaux in Histoire des chênes de l'Amérique describing the oaks found in the Americas. The word refers to the large fruit.

Links

Bur Oak iNaturalist taxon page
Bur Oak Plants of the World Online page
observations of Bur Oak in Manitoba
observations of Bur Oak in the world

Posted by marykrieger marykrieger, August 01, 2020 14:23

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