|Blank, Robert - Bob|
Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2005
Publication Date: 3/1/2006
Citation: Murphy, J.D., Johnson, D.W., Miller, W.W., Walker, R.F., Blank, R.R. 2006. Prescribed fire effects on forest floor and soil nutrients in a Sierra Nevada forest. Soil Science. 171:181-199. Interpretive Summary: Limited data are available, in Sierra-Nevada montane forests, which tests the effects of management practices to reduce the danger of catastrophic fires on soil nutrients. We investigated the effect of several forest thinning treatments and prescribed burning on carbon, nitrogen, ortho-phosphorus, and sulfate in the forest floor organic layer and surface soil mineral horizons. Relative to controls, prescribed fire decreased forest floor total carbon and nitrogen for all thinning treatments, but had relatively minor influence on water-extractable ortho phosphorus and sulfate. Irregardless of thinning treatment, prescribed fire had little impact on total and soluble nutrients in the upper mineral soil layer. Loss of nitrogen capital from the forest floor appears to be the major effect of prescribed burning.
Technical Abstract: The objectives of this study were to quantify the effects of prescription burning on forest floor and nutrient content, soil chemical properties, and soil leaching in a Jeffrey pine (Pinus jeffreyi [Grev. and Balf.]) forest in the eastern Sierra Nevada Mountains of California. The study included a prescribed fire and three timber harvest treatments: whole-tree thinning (WT) cut-to-length thinning (CTL), and no harvest (CONT). Prescribed fire resulted in significant decreases in forest floor C and N contents in all treatments, significant losses of forest floor S in the CTL treatment, and significant losses of forest floor K in the WT treatment. Burning caused significantly higher pH, water-extractable ortho-P, bicarbonate-extractable P, and water-extractable SO42- in some horizons of some treatments, but these effects were generally, small and, in the case of ortho-P, much less than the temporal variation in both burned and unburned plots. There were no statistically significant effects of burning on soil C, N, C:N ratio, Bray-extractable P, exchangeable Ca2+, K+, or Mg2+. Burning had no significant effect on soil solution pH, ortho-P, SO42-, NO3-, or NH4+ as measured by ceramic cup lysimeters and no effect on the cumulative leaching of ortho-P, NO3-, or NH4+ as measured by resin lysimeters. Burning had no effect on needle weight or nutrient contents as measured by the vector analysis. We conclude that the major effect of prescribed fire on the site was on the loss of N from the forest floor.