Response of Soil Denitrifying Communities to Long-Term Prescribed Burning in Two Australian Sclerophyll Forests

Low-intensity prescribed burning is a common forest management tool and plays a major role in modifying biogeochemical cycling through the alteration of substrate availability and microbial communities. In this study, we assessed the response of microbial community to repeated prescribed burning in two sclerophyll forests (the Bauple site, dry, annual rainfall 1000 mm; and the Peachester site, wet, 1711 mm) in southeast Queensland, Australia. At the dry sclerophyll forest (the Bauple site), annual and triennial burning did not significantly alter the soil carbon (C) and nitrogen (N) content, while at the wet scleophyll forest (the Peachester site), two yearly burnings resulted in significantly lower soil total C and N contents compared to the long unburnt treatment. In spite of these different responses, prescribed burning regimes did not significantly influence the abundance of 16S rRNA or denitrifying gene (narG, nirK, nirS, nosZ) at both sites. These results indicated that, long-term prescribed burning has little effect on the denitrifying communities, while it has varying effects on soil chemical properties at the two sites, which are likely to be explained by differences in vegetation type and soil moisture regime.