Wildfire mitigation strategies affect soil enzyme activity and soil organic carbon in loblolly pine (Pinus taeda) forests

Abstract

We quantified the effects of three wildfire hazard reduction treatments (prescribed fire, thinning from below, and the combination of fire and thinning), and passive management (control) on mineral soil organic C, and enzyme activity in loblolly pine (Pinus taeda L.) forests on the Piedmont of South Carolina. Soil organic C was reduced by thinning, either alone or with prescribed fire, and this effect persisted through the fourth post-treatment year. Fire also resulted in reduced soil organic C, but not until several years after treatment. Soil C/N ratio initially increased after fire, either alone or with thinning, but this difference did not persist. The activities of three soil enzymes (acid phosphatase, chitinase, and phenol oxidase) in the upper mineral soil were quantified as measures of microbial activity. During the fourth post-treatment year we observed significant stimulation of all three enzyme systems as a result of thinning or thinning and burning. Although the patterns of variation in acid phosphatase and chitinase activity among treatments were similar during the first and fourth post-treatment years, the first-year treatment effects were not statistically significant. Given the management objective of utilizing these stands for timber production, the increased potential for rapid nutrient turnover offered by thinning gives this approach advantages over prescribed fire; however, management for maximum long-term storage of soil C may be better facilitated by prescribed fire.

Soil labile organic carbon and carbon-cycle enzyme activities under different thinning intensities in Chinese fir plantations

“…Thinning reduced the SOC concentrations except for in October, which was partially consistent with our hypothesis, and the thinning effect was more pronounced in the upper soil layer than in the lower. An average SOC loss of 32.5% SOC in thinned sites was also found by Boerner et al (2006), whereas Achat et al (2015) found an SOC decrease of approximately 7% by tree removal in a meta-analysis. The decrease in SOC following the partial removal of canopy trees has been attributed to the reduction in the supply of substrate that enters the soil (Piene and Cleve, 1978;Jandl et al, 2007).…”

Recovery of soil microbial community structure after fire in a sagebrush‐grassland ecosystem

“…A study by Boerner et al (2006) also reports the reduction of SOC after prescribed fire. The highest pH values were found in the Establishment and Expansion stages, which also had the highest microbial community structure.…”

Soil microbial responses to fire and interacting global change factors in a California annual grassland

“…Chemically, low-severity fires deposit plant ash residues that contain macronutrients and organic carbon (Boerner et al 2006). Specifically these include: carbonates of alkaline earth metals, silica, heavy metals, sesquioxides, phosphates, and organic and inorganic N (Raison 1979;Grogan et al 2000;Wan et al 2001;Picone et al 2003;Li and Herbert 2004;Boerner et al 2006).…”

“…Specifically these include: carbonates of alkaline earth metals, silica, heavy metals, sesquioxides, phosphates, and organic and inorganic N (Raison 1979;Grogan et al 2000;Wan et al 2001;Picone et al 2003;Li and Herbert 2004;Boerner et al 2006). Additionally, heating from fire can volatilize nitrogen in the top few centimeters of the soil horizon (Wan et al 2001).…”