PARENT SESSION
Monday, August 7, 5:00-6:30 pm
Poster Session 1 - Disturbance ecology
Exhibit Hall, Ballroom Level, Cook Convention Center
Soil heating in a range of grass fire conditions and subsequent effect on belowground grass organs.
Choczynska, Joanna*,1, Johnson, Edward1, 1 University of Calgary, Calgary, AB, Canada
ABSTRACT- Grasses contain regenerative tissues (buds) in the crown, on aboveground stems, at the base of crowns (located at or just below the soil surface), and on belowground organs called rhizomes. Aboveground matter is typically consumed during a fire, and the grass' survival depends on the ability to resprout from surviving tissues. We used a soil heat and water transport model to look at the potential of fires to impact the rhizome bud distributions of three tallgrass species (Andropogon gerardii, Sorghastrum nutans, and Panicum virgatum). Most buds are found at depths of 1 to 4 cm below the soil surface, with a subsequent decline in the number of buds with depth. Little or no buds are found below 6 cm. Soil heating is described by physical processes including conduction of heat through the soil, and heating and evaporation of water. We consider factors including soil moisture, texture, mineral thermal conductivity, maximum soil surface temperature and fire residence time. Soil temperature profiles are combined with bud distributions to determine the proportion of buds expected to be heated to lethal temperatures under a specific set of conditions. Our modeling approach allows us to account for a range of conditions that can be realistically encountered in the field, and to combine the effect of multiple factors. Results show that lethal temperatures are only reached to depths of 1 or 2 cm and at least 30% of rhizome buds remain below lethal temperatures, even when extreme fire and soil conditions are selected. Several hours of heating at a high temperature are required to kill all buds, which is an unrealistic situation in a grass fire. This implies that grasses are expected to survive direct heat effects from a fire, and that changes in fire and soil conditions do not notably impact soil temperatures and rhizome bud survival.
Key words: fire ecology, grassland, modeling