Short-Term Fire-Induced Changes in Soil Microbial Community and Nutrients in Subtropical Native Rangelands

Abstract Background- Prescribed burning is a widely used management strategy to maintain ecosystem function and reduce the risks of wildfire. However, fire can alter soil microbial community, with subsequent impacts on soil carbon (C), nitrogen (N), and phosphorus (P) cycling. We examined the short-term effects of prescribed burning on selected soil chemical properties, soil enzyme activities, and bacterial and fungal community composition in subtropical native rangelands. Fire-induced responses were assessed immediately and 2 to 3 months after a fire event. Results- Soil pH, total C, and extractable NH4+and P concentrations decreased immediately after fire and remained relatively lower than the initial conditions 2 to 3 months after fire. Total N increased immediately after fire but returned to initial condition 2 to 3 months after fire. No effect of fire were observed for soil total P, and extractable Ca, K, Mg, Mn, Fe, and Al concentrations. Reductions in soil beta glucosidase and N-acetyl glucosaminidase activity were observed immediately following fire but no differences occurred 2–3 months after fire. Microbial diversity and relative abundance at the phylum level revealed no short-term changes, but at the order level Desulfurellales increased while Eurotiales and Pleosporales decreased immediately after fire. Conclusions- Our results demonstrated that the prescribed burning had a minimal soil effect on soil microbial community composition in the short-term, probably due to limited effects in soil temperature associated with rapid vegetation recovery. This suggest that managers can employ prescribed burning to obtain the multiple benefits without major long-term impacts on the biogeochemical cycle of C, N, and P. Our study offers the potential to assess the suitability of the prescribed burning and future studies related to soil nutrient availability in subtropical regions for rangeland management. Long-term assessment is needed to determine if the effect of prescribed burning takes place in different time scales that will help us better predict changes in ecosystem function to changing fire regimes.