Influence of post-fire root decay-induced soil macropores on slope stability: A new method for analyzing heterogeneous slope stability

Abstract

Soil macropores are key factors affecting slope hydrological processes and stability, particularly under heavy rainfall conditions. Although wildfires can lead to the decay and death of plant roots, leaving root channels, few studies have examined temporal variation in the distribution of soil macropores or their impact on slope stability. To address this, we examined the bacterial abundance, root distribution, and macropore characteristics of burnt forest at one week and 6 and 12 months post-fire. Numerical simulation was used to analyze the effects of macropore distribution on slope stability under extreme rainfall conditions (80 mm/d × 4 d) at each time-point. Soil macropores accelerated the propagation of water pressure, potentially triggering shallow-slope instability. In the simulation, following 1 d of rainfall, slope stability was lower, by 3.55% and 8.68%, respectively, at 6 and 12 months than at one week post-fire. Following 4 d of rainfall, slope stability was better at 6 and 12 months than at one week post-fire, by 1.87% and 2.81%, respectively, owing to the drainage effect of the macropores. Even more importantly, this study proposed a method for coupling the spatial heterogeneity of soil macropores with a numerical model of slope stability. These findings help to elucidate the temporal changes in vegetated slope hydrology and stability after a wildfire and provide a reference for the numerical simulation of the stability of heterogeneous slopes.