Post-fire recovery of soil microbial functions is promoted by plant growth

Abstract

Forest fires can alter the biological properties of soils. There is increasingevidence that fires cause a shift in soil microbial communities, which play acentral role in forest carbon and nutrient cycling. In this study, we evaluatethe effect of soil heating on soil microbial functions. We hypothesised that firereduces the catabolic functional diversity of soil, and that post-fire plantgrowth enhances its recovery. To test this, we experimentally heated a forestsoil at 200 C (T200) or 450 C (T450). Heated and unheated soils were thenincubated in tubs with or without live grass (Lolium perenneL.). We deter-mined the functional profiles by measuring the substrate-induced respiration(SIR) using the Microresp¿technique and analysed nutrient availability atthe end of the incubation. At both temperatures, soil heating altered the respi-ration responses to substrate additions and the catabolic functional diversity ofsoils. Functional diversity was initially reduced in T200 soils but recovered atthe end of the incubation. In contrast, T450 soils initially maintained the cata-bolic functional diversity, but decreased at the end of the incubation. Heating-induced nutrient availability stimulated the growth of grass, which in turnincreased the response to several substrates and increased the functional diver-sity to values similar to the unheated controls. Our results suggest that fire-driven alteration of soil microbial communities has consequences at a func-tional level, and that the recovery of plant communities enhances the recoveryof soil microbial functions.