After writing a recent post about fire effects for fall burning, a couple of interesting papers that speak to season of fire have crossed my desk. Both studies hailed from Texas and evaluated summer and winter burning in savanna. Although they measured different variables, both studies saw more pronounced effects of summer fire than winter fire.
Taylor et al. (2012) found that summer burning maintained live oaks while reducing other undesirable plants. Winter fires maintained the woody plants in the overstory but increased them in the understory, except for Ashe juniper. Winter burns also altered the frequency of grasses, in particular by increasing little bluestem.
Ansley et al. (2006) looked at the effects of burning in winter or summer on the soil nutrient pools. Interestingly, whole plant mortality was <5% for both seasons, but summer fire seemed to be more effective for topkilling plants. Mesquite resprouted more frequently in the summer fire treatments. C3 grasses (cool season) increased over controls in both fire seasons. Black carbon did not differ meaningfully between treatments or controls. Soil organic carbon and nitrogen increased as a result of summer fire, likely because of increased fire root production (indicated by greater primary production). Winter fire had no effect on soil organic carbon or nitrogen.
Together these projects, as well as the ones described in the fall burning post, indicate that the timing of prescribed fire can help managers work toward achieving specific objectives. Despite the differences between burning in different seasons, the biggest differences in many target variables may occur when comparing areas treated with prescribed fire to those with no fire treatment.
Ansley, R. J., T. W. Boutton, and J. O. Skjemstad. 2006. Soil organic carbon and black carbon storage and dynamics under different fire regimes in temperate mixed-grass savanna, Global Biogeochemical Cycles, 20, GB3006, doi: 10.1029/2005GB002670.
Taylor, C. A. Jr., D. Twidwell, N. E. Garza, C. Rosser, J. K. Hoffman, and T. D. Brooks. 2012. Long-Term Effects of Fire, Livestock Herbivory Removal, and Weather Variability in Texas Semiarid Savanna. Rangeland Ecology & Management: January 2012, Vol. 65, No. 1, pp. 21-30.