|White, Robert - USDA-FS|
|Ziska, Lewis - USDA-ARS|
Submitted to: International Journal of Wildland Fire
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2006
Publication Date: June 1, 2006
Citation: Blank, R.R., White, R., Ziska, L. 2006. Combustion properties of bromus tectorum l.: influence of ecotype and growth under four co2 concentrations. International Journal of Wildland Fire. 15:227-236 Interpretive Summary: Data on the influence of atmospheric CO2 concentration on combustion properties of vegetation is almost non-existent. Using a cone calorimeter, we measured combustion characteristics of the invasive annual grass Bromus tectorum as affected by growth in four different concentrations of atmospheric CO2. Total heat released was significantly less for plants grown at pre-industrial CO2 compared to plants growth at higher CO2 concentration. Combustion of vegetation as atmospheric CO2 increase may be more complete due to less char formation.
Technical Abstract: We grew from seed, the exotic invasive annual grass Bromus tectorum L. collected from three elevation ecotypes in northern Nevada, USA. Plants were exposed to four CO2 concentrations: 270, 320, 370, and 420 ppm. After harvest on day 87, aboveground tissue was milled, conditioned to 30% relative humidity, and combustion properties were measured using a cone calorimeter. Plants exposed to 270 ppm CO2 had significantly less total heat released than plants exposed to higher CO2 concentrations. Total heat released was least for the low elevation ecotype, statistically similar for the mid elevation ecotype, and significantly increased for the high elevation ecotype. Plant attributes that significantly correlated with heat release included tissue concentrations of lignin, glucan, xylan, K, Ca, and Mn. The data suggest that a decline in tissue concentrations of lignin, xylan, and mineral constituents, as CO2 concentration increases from 270 ppm to higher levels, affects the combustion process. We suspect that as tissue concentrations of lignin and inorganics decline, char formation decreases thereby allowing more complete combustion. Changes in combustion parameters of B. tectorum induced by different CO2 concentrations and elevation ecotype may be a strong consideration to understanding fire behaviors of the past, present, and future.