Permafrost degradation due to fire disturbance: A case study in the Da Xing’anling mountains, Northeastern China

Abstract

Xing’an permafrost (XAP), widely distributed in the Da Xing’anling Mountains in northeastern China, is an ecosystem − dependent permafrost type that is highly sensitive to vegetation and surface insulation. To investigate its response to a unique form of human − induced fire disturbance (HIFD) — prescribed firebreak burning (PFB) — an on − site monitoring system was established in a PFB − affected area. Ground temperatures were continuously recorded from 2019 to 2024 to assess the thermal effects of PFB. Meanwhile, electrical resistivity tomography (ERT) testing was conducted in the PFB region. The recorded data indicated that, as a result of PFB, thawing interlayers were formed in cold seasons, and the thawing interlayer base gradually moved downwards. The seasonal thawing depth (STD) was observed to increase in warm seasons. Ground temperatures in deeper strata continued to rise, but the rate of permafrost warming gradually decreased with increasing depth. The permafrost thickness was found to continuously decrease. In future, with continuous PFB, the XAP is expected to experience complete degradation. The ERT profiles showed a smaller permafrost area and higher ground temperatures in the PFB region than in the areas without PFB, with the rise of ground temperature being most pronounced in the shallowest stratum. Water ponding and human construction practices also contributed to the severe degradation of the XAP, but the influencing mechanism on the permafrost differs for the three types of disturbance. The findings of this study provide a reference for studies of the effect of PFB on the evolution of XAP, and also provide guidance for the installation of fire isolation barriers in XAP regions of northeastern China.