Changes in understory production for three prescribed burns of different ages in ponderosa pine

The general lack of resource response information severely limits economic evaluation of prescribed burning in most forest types. This paper present changes in understory production at three sites on basalt soils following prescribed burning in ponderosa pine (Pinus ponderosa Laws.) in Arizona. The sites were burned during the fall 2, 5, and 7 years before sampling in 1981. Regression equations were developed to predict production from plant basal area for four common grass species; production of remaining herbaceous vegetation was measured by harvesting. Based on the results of our study and other studies of fall prescribed burning on volcanic soils in Arizona ponderosa pine, understory production response appears to be variable for 1-2 years following burning. Herbage production exhibits no change or an increase; forage production exhibits no change or a decrease. Studies of understory response more than 2 years following both wildfire and prescribed burning in Arizona ponderosa pine, however, show a general trend toward increased production. Thus, prescribed burning in southwestern pine on basalt soils produces long-term benefits in increased understory production, particularly in pole stands, which dominate much of the region.