Fire temperatures in plant communities of the northern mixed prairie

Abstract

Temperatures during prescribed spring burns were monitored for selected mixed prairie plant communities near Saskatoon, Saskatchewan. In fescue, spear grass, and brome communities the fires peaked quickly at an average maximum temperature of approximately 500°C, then reverted to ambient conditions within about 1 minute. The highest temperatures were recorded 10 cm aboveground. A temperature of 60°C was considered the upper tolerance limit for plant tissue; such conditions persisted for approximately 1 minute within the grass stands. Similar temperatures were observed in a stand of Silverberry. Temperatures above 800°C were recorded in snowberry and aspen and a more protracted cooling phase was noted because of the coarser woody fuel. In all grass and shrub stands there was little change in temperature in the mineral soil at a depth of 5 cm. However, in the aspen grove average temperatures at this depth increased to about 450°C because the thermocouple was embedded in the thick litter layer.