Can Mowing Substitute for Fire in Semiarid Grassland?

Abstract

Accumulating data indicate the importance of fire in rangeland systems. Mowing is a common management technique sometimes considered a surrogate for fire. However, direct comparisons of fire and mowing effects are limited. Our objective was to determine whether mowing can substitute for fire in rangeland by comparing effects on plant biomass, composition, cover, soil nutrients, and forage quality. Three disturbance treatments (nontreated control, spring mowing with clipping removal, and spring fire) were randomly assigned to 21 plots (5 × 5 m) each on silty and claypan ecological sites in a completely randomized design, with seven replications per site. Current-yr biomass was similar among control, mowed, and burned treatments (1 003, 974, 1 022 ± 64 kg ● ha− 1). Mowing shifted functional group composition by reducing C<inf>3</inf> perennial grass 12% and increasing forbs 8%. Non-native species were a larger component of mowed (12%) than control (6%) or burned plots (4%). Fire increased bare ground 35%, reduced litter 32%, and eliminated previous yrs’ growth the first growing season. Plant-available soil N and S more than doubled with fire, and there was a trend for more P in burned plots. Mowing effects were limited to a trend for less soil Fe. Mowing affected 42% of the forage quality variables with a 2% average improvement across all variables. Fire affected 84% of the variables, with a 12% average improvement. Mowing increased forage P and K, whereas fire increased forage concentrations of N, K, P, S, Mg, Fe, Mn, and Cu. Total digestible nutrients increased 1.1% with mowing and 2.1% with fire. In vitro dry matter disappearance increased 2.2% with mowing and 6.7% with fire. Burned plots had greater in vitro fermentation than controls or mowed plots. Although mowing can be a useful management tool, it is not a substitute for the ecological effects of rangeland fire. © 2019