Ponderosa Pine Biomass Relationships Vary with Site Treatment and Site Productivity

Allometric equations, which express biomass as a function of tree size, are often used to estimate the amount of fuel in a site’s canopy. Most managers assume that one allometric equation per species is sufficient, or that any error introduced by extrapolation is irrelevant. This work showed, however, that the allometric biomass relationship for ponderosa pine likely changes over space and time. The researchers concluded that for maximum accuracy, allometric equations for ponderosa pine should account for stand management history and site productivity. Thinned trees replaced their foliage within about 4 years, and 8–10 years post-thinning, growth had stabilized. This indicates that using allometric equations to estimate fuel loads can result in miscalculation of the potential for active crown fire.Key Findings In ponderosa pine, the relationship between foliage biomass and tree dimensions varies in response to thinning. Forest productivity may influence biomass relationships for ponderosa pine trees. Stand-level foliage biomass reached pretreatment levels within 5 years post-thinning. Overall fire risk may be lower because ladder fuels were removed, but heavy litterfall rates could still support frequent surface fires.