STAND DENSITY INDEX AS A PREDICTOR OF FORAGE PRODUCTION IN NORTHERN ARIZONA PINE FOREST

Ponderosa pine (Pinus ponderosa Laws.) overstory-forage understory relationships were studied on the Kaibab Plateau of northern Arizona to evaluate how well forage (graminoid, forb,. and current year shrub) production could be predicted by stand density index (SDI). Linear and nonlinear equations were used. Stand density index, a relative measure of stand density, was a useful predictor of understory production for a variety of stand structures and ages. The linear and nonlinear equations produced coefficient of determinations of 0.76 and 0.72, and standard error of the estimates of 5.08 kg ha-1 and 5.51 kg ha-1, respectively.