Sagebrush wildfire effects on surface soil nutrient availability: A temporal and spatial study

Authors: Blank, Robert - Bob; Clements, Darin - Charlie; Morgan, Tye; Harmon, Daniel - Dan

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2017
Publication Date: 5/23/2017
Citation: Blank, R.R., Clements, D.D., Morgan, T.A., Harmon, D.N. 2017. Sagebrush wildfire effects on surface soil nutrient availability: A temporal and spatial study. Soil Science Society of America Journal. 81(5):1203-1210. https://doi.org/10.2136/SSSAJ2017.02.0039.
DOI: https://doi.org/10.2136/SSSAJ2017.02.0039

Interpretive Summary: Wildfires occurring in sagebrush ecosystems can temporarily increase surface soil nutrient availability. In Oct. 2013, a wildfire approximately 30 km north of Reno, Nevada occurred in an mountain big sagebrush community. We quantified soil nutrient availability of surface soil (0-10 cm) by microsite (shrub interspace and shrub canopy), treatment (burned and unburned), and temporally (monthly from Nov., 2013 through May, 2015). Changes in nutrient availability, due to wildfire, largely occurred in shrub canopy microsites. For most months and relative to unburned shrub canopies, burned shrub canopies had elevated availability of mineral N (dominantly NH4+-N), bicarbonate-extractable P, DTPA-extractable Mn, and solution-phase Ca+2, Mg+2, SO4-2, K+, and ortho-P. Burned shrub canopies also had, for most months, far less N mineralization potentials than unburned shrub canopies. Except for a slight increase in solution-phase Mg+2, SO4-2, and ortho-P for particular months, there was little evidence of nutrient movement from burned canopies to adjacent interspaces during the study. Increased soil Mn availability following wildfire may potentially benefit, as does increased mineral N, the exotic invasive annual grass Bromus tectorum (cheatgrass).

Technical Abstract: Wildfires occurring in Artemisia (sagebrush) ecosystems can temporarily increase soil nutrient availability in surface soil. Less is known, however, on how soil nutrient availability changes over time and microsite location post-wildfire. In Oct., 2013 a wildfire approximately 30 km north of Reno, Nevada occurred in an Artemisia tridentata subsp. vaseyana (mountain big sagebrush) community. We quantified soil nutrient availability of surface soil (0-10 cm) by microsite (shrub interspace and shrub canopy), treatment (burned and unburned), and temporally (monthly from Nov., 2013 through May, 2015). Changes in nutrient availability, due to wildfire, largely occurred in shrub canopy microsites. For most months and relative to unburned shrub canopies, burned shrub canopies had elevated availability of mineral N (dominantly NH4+-N), bicarbonate-extractable P, DTPA-extractable Mn, and solution-phase Ca+2, Mg+2, SO4-2, K+, and ortho-P. Burned shrub canopies also had, for most months, far less N mineralization potentials than unburned shrub canopies. The large increase in Mn availability in burned shrub canopies significantly correlated with mineral N and solution-phase Ca+2 and SO4-2, suggesting release via pyrolysis of soil organic matter. For many paired variables, the strongest linear relationship occurred beneath burned shrub canopy microsites. Except for a slight increase in solution-phase Mg+2, SO4-2, and ortho-P for particular months, there was little evidence of nutrient movement from burned canopies to adjacent interspaces during the study. Increased soil Mn availability following wildfire may potentially benefit, as does increased mineral N, the exotic invasive annual grass Bromus tectorum (cheatgrass).