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See also presentation by Beth McEwen and Jennifer Gibb, City of Toronto, Forestry, at a Wildland Fire Canada conference in October 2010.
Prescribed burns are part of Urban Forestry’s long-term management goal to restore and protect Toronto’s rare black oak woodlands and savannahs. A prescribed burn is a deliberately set and carefully controlled low fire that
consumes dried leaves, small twigs and grass stems, but does not harm larger trees.
Since 2000 City of Toronto Urban Forestry has been using fire as a management tool to help restore and expand High Park native plant communities including the globally rare Black Oak savannah habitat.
Prior to settlement, fire played a pivotal role in maintaining the prairies, savannahs and oak forests that once extended across southern Ontario. Fire is an important factor in a healthy oak savannah as it helps to encourage and invigorate native species that have evolved to persist in fire controlled systems.
Prairie plants including black oaks respond to modified site conditions following the burn, and grow more vigorously than they would have in the absence of the fire. Fire also works in reducing competition from some invading exotic species that are not adapted to a fire controlled ecosystem.
The natural fire cycle had been suppressed in High Park for over 100 years, and although regular fires have only been occurring for about 9 years, large improvements are already being observed in the distribution and health of native plant species in the park. Currently, a total of 37 ha of oak savannah and woodland areas are burned on a rotating cycle. The initial goals for the prescribed burn program established in the management plan focused on enhancing the growth of native species while controlling exotic plant species. Special attention was also focused on targeting small rare plant communities existing in High Park in the hope of encouraging their natural expansion. Annual monitoring for the past several years has shown that many areas in High Park are exhibiting large increases in native plant community patches, as well as a significant decline in some of the exotic species controlled by burning, such as garlic mustard.
Perhaps one of the largest success stories to result from the burning of High Park involves the story of the wild lupine. Following the first prescribed burn in 2000, the wild lupine populations exhibited immediate response, and increases in patch size as well as seed crop were observed the next season. The wild lupine is an important species of interest due to its special relationship with the extirpated Karner blue butterfly. As the only food source for the larva of the Karner blue butterfly, the wild lupine population directly affects any attempt to reintroduce this species to High Park and other sites in Ontario. Although it is unlikely that the Karner blue butterfly would be reintroduced to a highly urbanized park like High Park (except perhaps after it becomes firmly re-established in other sites in Ontario), it is possible that the lupine plants at High Park could be used as a seed source for other sites and for research purposes.
Although the wild lupine may be the most well known species to have benefited from burning, High Park is home to many rare and important species also thriving from prescribed burning. Species in the drier savannah areas are showing large success in expansion such as dryland blueberry, Indian grass, big bluestem, woodland sunflower, sky-blue aster, and a variety of goldenrods and sedges.
In the beginning stages of the prescribed burn program, frequent burns were necessary to reverse the effects of the approximately 100 years of suppressed fire cycles. More frequent burning was required to set-back exotic invasive plants such as buckthorn & honeysuckle to allow more light to penetrate into the savannah habitats.
As the successes of the High Park prescribed burn program continue, the frequency and interval between burns will need to be reevaluated and adjusted accordingly.
Source: City of Toronto Notice April 2008