Wildfire exerts a long-term impact on soil multifunctionality by influencing soil environments and vegetation regeneration in a Chinese boreal forest

Abstract

Background and aims Wildfires can trigger significant changes in soil functioning in boreal forests, and fire-caused changes in soil environments and vegetation community can further affect soil functioning. However, the response of multiple simultaneous soil functions (i.e. multifunctionality) to wildfire and postfire changes in soil environments and regeneration vegetation remains unknown though soil multifunctionality (SMF) is crucial to the biogeochemical cycling and plant growth. Methods We sampled 60 soils at unburned control, 1-year-postfire, and 11-year-postfire sites in a Chinese boreal larch forest to explore the relationships between SMF and fire severity, bacterial diversity, soil environments and regenerated vegetation. Results The SMF was lower at the two burned sites relative to the control, decreasing with increased fire severity but increasing with soil bacterial diversity. Structural equation modeling analysis confirmed that fire severity was the most important predictor of SMF at the 1-year-postfire site, while SMF at the 11-year-postfire site was mainly mediated by soil moisture besides fire severity, regenerated tree density and grass cover. Conclusions Wildfire exerts a long-term negative effect on SMF and this effect is closely related to fire severity and bacterial diversity in the Great Xing’an Mountains. The effects of wildfire on SMF might be directly mediated by fire severity in the short term but indirectly by altering soil environments and vegetation regeneration in the long term. We conclude that increasing fire severity of these forests can both directly decrease SMF and trigger the degradation of their soil-plant ecosystems, which would further imperil the maintenance of SMF.