U.S. Joint Fire Science Program


Date of this Version


Document Type



Fire Science Brief, Issue 92, February 2010


US government work.


Nitrogen availability in soils, streams and associated terrestrial and aquatic vegetation can be infl uenced by both wildfi res and prescribed burns, though typically not to the same degree. Extensive research was done on postfire nitrogen dynamics at several mid-altitude coniferous National Forest sites in Idaho. Sites included both wildfi relocations and prescribed burn projects. By measurement of both ammonium (NH4) and nitrate (NO3) levels, researchers documented over time the effects of both high-intensity wildfi res and lower-intensity prescribed burns on nitrogen transformation processes in soil levels, and nitrogen levels in various ecosystem components. Field measurements demonstrated that the soil, water and foliage nitrogen effects of low-intensity spring prescribed fi res are quite different from the nitrogen dynamics of wildfi res. Wildfires in these western forests produced significant (three year plus) pulses of nitrogen to aquatic systems, compared to very limited pulses from spring prescribed burns.