Drivers of changes in soil properties during post-fire succession on Dahurian larch forest

Soil properties play key roles in ecosystem recovery at the landscape scale and are regulated by a complex interplay between abiotic and biotic factors. Our study aimed to identify the potential drivers of post-fire changes in mineral soil in the larch forest of southeastern Siberia. We established a 28-year fire chronosequence with 80 sites over a small region of the Greater Khingan Range. At each site, we measured topographic factors, arboreal variables, and ten physical and chemical attributes of surface mineral soils. We used the hierarchical clustering analysis, distance-based redundancy analysis, variation partitioning analysis, Random Forest analysis, and structural equation modeling to disentangle the drivers for the coupled and decoupled patterns in soil properties. The results showed that time since fire is an ecological predictor that cannot be completely discarded for the soil property prediction model. Wildfires altered the effects of topography and arbors on soil properties. Compared with the unburned area, the soil properties of the burned area were associated more with explanatory variables. Here, altitude was a powerful topographic factor that positively correlated with soil properties, whereas slope position, gradient, and aspect had more negative and less positive effects on soil fertility and exhibited similar patterns, of which slope position and gradient exerted stronger influences than aspect. The importance ranking of average tree size was not significantly changed by fires though its relationship with the soil was obviously changed. In boreal larch forest, wildfires enhance the impact of topography on soil properties while decreasing the impact of arbors on soil properties. Although the arbors are not as critical as topography to the change of soil properties in a few decades after fire, the importance of arbors tends to gradually increase over many years. Consequently, wildfires can cause an on-going shift in the importance and the relative importance of topography and arbors on soil properties in boreal larch forest.