Fires affect hundreds of millions of hectares annually. Above-ground community composition and diversity after fire have been studied extensively, but effects of fire on soil bacterial communities remain largely unexamined despite the central role of bacteria in ecosystem recovery and functioning. We investigated responses of bacterial community to forest fire in the Greater Khingan Mountains, China, using tagged pyrosequencing. Fire altered soil bacterial community composition substantially and high-intensity fire significantly decreased bacterial diversity 1-year-after-burn site. Bacterial community composition and diversity returned to similar levels as observed in controls (no fire) after 11 years. The understory vegetation community typically takes 20–100 years to reach pre-fire states in boreal forest, so our results suggest that soil bacteria could recover much faster than plant communities. Finally, soil bacterial community composition significantly co-varied with soil pH, moisture content, NH4+ content and carbon/nitrogen ratio (P < 0.05 in all cases) in wildfire-perturbed soils, suggesting that fire could indirectly affect bacterial communities by altering soil edaphic properties.

Aims Wildfires are important disturbances that help to shape the structure and function of forest ecosystems, and arbuscular mycorrhizal fungi (AMF) are key players in the post-fire recovery of soils and understory vegetation. We aimed to investigate the response of AMF communities to wildfire over different timescales. Methods Primer set AMV4.5NF/AMDGR was used to amplify soil 18S rRNA gene fragments for the 454 GS-FLX pyrosequencing platform to examine belowground AMF communities 1 and 11 years following low-and high-intensity wildfires in the Greater Khingan Mountains of China. Results The majority of AMF sequences detected were annotated as Glomeraceae, Claroideoglomeraceae, Diversisporaceae and Acaulosporaceae. Both AMF community composition and alpha-diversity were correlated with herbaceous and shrubby biomass, available phosphorus (AP) and NH 4 + , which were in turn altered by wildfire. AMF community composition, alpha-diversity, and phylogenetic structure were significantly altered 1-year-post-fire. However, AMF communities were indistinguishable from unburned forest soils 11-year-post-fire. Conclusions Our results indicated that AMF communities are resilient to wildfire on decadal timescales. This resilience appears to depend on the post-fire regrowth of understory vegetation and the subsequent recovery of soil chemical properties.