Wildfire effects on forest carbon and nutrient budgets

A wildfire burned through previously established research plots, allowing comparisons of pre- and post-fire nutrient pools and fluxes. The Gondola fire resulted in the loss of 30.9 mg ha−1 of C and 510 kg ha−1 of N, mostly by the combustion of forest floor and vegetation. Mineral N leaching was accelerated for 3 years after the fire, but accounted for only 19 kg ha−1 of the total N loss. Potential inputs of P by ash were small relative to soil extractable pools and no significant changes in soil extractable P were noted. No changes in exchangeable K+ were noted, even though inputs by ash could have been detected, suggesting that K was lost either during or after the fire. Similarly, decreases in soil exchangeable Mg2+ were noted even though ash inputs should have caused notable increases, suggesting Mg loss either during or after the fire. The increases in soil-exchangeable Ca2+ were large, but only marginally significant (P = 0.09) and fell within the error bounds of what could have been input from ash. Comparisons with a nearby site that burned >20 years previously suggest that ecosystem C pools will not be made up for until trees are re-established at the Gondola fire, whereas N losses could be more than made up for within 20 years if N-fixing vegetation colonized the site.