Canadian Forest Service Publications

Characterisation of the fuel and fire environment in southern Ontario's tallgrass prairie. 2015. Kidnie, S.; Wotton, B.M. International Journal of Wildland Fire [in press] -- http://www.publish.csiro.au/paper/WF14214.htm

Year: 2015

Available from: Great Lakes Forestry Centre

Catalog ID: 36438

Language: English

CFS Availability: PDF (request by e-mail)

Abstract

Prescribed burning can be an integral part of tallgrass prairie restoration and management. Understanding fire behaviour in this fuel is critical to conducting safe and effective prescribed burns. Our goal was to quantify important physical characteristics of southern Ontario’s tallgrass fuel complex prior to and during prescribed burns and synthesise our findings into useful applications for the prescribed fire community. We found that the average fuel load in tallgrass communities was 0.70 kg m–2. Fuel loads varied from 0.38 to 0.96 kg m–2. Average heat of combustion did not vary by species and was 17 334 kJ kg–1. A moisture content model was developed for fully cured, matted field grass, which was found to successfully predict moisture content of the surface layers of cured tallgrass in spring. We observed 25 head fires in spring-season prescribed burns with spread rates ranging from 4 to 55 m min–1. Flame front residence time averaged 27 s, varying significantly with fuel load but not fire spread rate. A grassland spread rate model from Australia showed the closest agreement with observed spread rates. These results provide prescribed-burn practitioners in Ontario better information to plan and deliver successful burns.

Plain Language Summary

Small prescribed fires are common during the spring in southern Ontario. These are typically used to restore important ecosystems like tallgrass prairie that used to be common but need to burn often to survive competition from other species. Our measurements showed that the amount of grass that can burn in tallgrass prairies was double the amounts we typically find in typical field grass. Fire spread rates and fire intensities had been observed by prescribed burners to be higher than our existing models predicted and for safety it was necessary to understand and better predict fire behaviour for the tallgrass prairie. We carried out fire behaviour observations on prescribed burns from 2007 to 2010 and tested several grassland fire spread rate models to see which worked best. Observations showed a model from Australia grasslands provided good predictions. Our work also showed that a model we had developed that uses weather to estimate moisture content of grass also worked well in tallgrass prairie. In addition to this research paper, we developed a field guide for predicting fire behaviour in this type of fuel.

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