Prescribed fire is a management practice used to reduce woody plant encroachment on rangeland and maintain native perennial grass diversity and productivity. Prescribed fire effects on CO2 fluxes and their contribution to atmospheric CO2 is not well known. The study below discusses the effect of fire on net ecosystem CO2 flux above Prosopis glandulosa Torr. (honey mesquite) using the Bowen ratio/energy balance method (BREB), and to compare these fluxes to fluxes determined by an empirical model.
Measurements were made during a wet year and a dry year with different savanna areas burned in late winter (Feb.-March) each year. During the wet year, BREB-estimated daily CO2 flux averaged -Q.1, 14.6, and 0.8g/m2 on the unburned plot. On the burned plot during the spring, summer, and fall periods, the daily averages were 15.7, 19.7, and 15.2 g/m2 following the first growing season after the fire.
During the drought year, mean daily CO2 flux during spring, summer, and fall was -9.2, 4.1, and 4.8 g/m2 on the unburned plot. The burned plot was 8.1, -0.9, and 4.6 g/m2.
The increased carbon uptake following a fire when compared to the unburned plot was estimated to offset the initial carbon loss from combustion within 28 growing-season days in the wet year. In the dry year, it took 82 growing season days.
It is estimated that by the end of the first growing season following the burn, the amount of carbon emitted during the burn had been taken up by the regrowing vegetation in both a wet and drought year.
For more information, be sure to check out the full study – Bowen Ratio/Energy Balance and Scaled Leaf Measurements of CO2 Flux over Burned Prosopis Savanna
Ansely R’ J’ et al. “Bowen Ratio/Energy Balance and Scaled Leaf Measurement of CO2 Flux over Burned Prosopis Savanna.” Ecological Application, 12(4), 2002, pp.848-961