Context Forest fires are key ecological factors affecting pine forests globally. Understanding impacts of varying fire intensities on forest ecosystem components is crucial for predicting recovery and informing management. Objectives This study aimed to assess effects of different surface fire intensities on structural components of pine forests, including tree canopy, herbaceous layer, and surface soil horizons, and identify relationships between fire intensity and ecosystem parameters. Methods The study examined three areas with different fire intensities (severe, moderate, mild) 1 year after a surface fire in Ukraine's Volyn-Polissia region, using vegetation surveys, soil analyses, and statistical methods. Results Fire intensity significantly influenced tree mortality and the vitality structure of Pinus sylvestris stands. Scorch height correlated strongly with stem diameter in mild and moderate intensity zones (P < 0.0001). Herbaceous layer composition showed significant variations in all life-form traits across different fire intensities. Species diversity, dominance, and evenness indices varied with fire intensity, as did species distribution by ecological strategies. Soil physicochemical properties, including surface layer density, ash content, moisture capacity, and pH, also changed. Correlations were found between the condition index of P. sylvestris and soil pH, as well as between herbaceous cover dominance/evenness indices and P2O5 content in surface soil layers. Weaker associations were identified between herbaceous cover diversity and soil density/hygroscopic moisture. The study was conducted over a 1-year period following the fire event, focusing on the short-term responses of vegetation and soil properties. Conclusions Surface fires of varying intensities alter multiple forest ecosystem components. Severely damaged areas may require restoration efforts, including active interventions such as artificial reforestation or other measures to accelerate recovery processes. Moderately and mildly affected zones, on the other hand, show potential for natural self-regulation. These findings have important implications for post-fire forest management strategies.

Permafrost regions play an important role in global carbon and nitrogen cycling, storing enormous amounts of organic carbon and preserving a delicate balance of nutrient dynamics. However, the increasing frequency and severity of wildfires in these regions pose significant challenges to the stability of these ecosystems. This review examines the effects of fire on chemical, biological, and physical properties of permafrost regions. The physical, chemical, and pedological properties of frozen soil are impacted by fires, leading to changes in soil structure, porosity, and hydrological functioning. The combustion of organic matter during fires releases carbon and nitrogen, contributing to greenhouse gas emissions and nutrient loss. Understanding the interactions between fire severity, ecosystem processes, and the implications for permafrost regions is crucial for predicting the impacts of wildfires and developing effective strategies for ecosystem protection and agricultural productivity in frozen soils. By synthesizing available knowledge and research findings, this review enhances our understanding of fire severity's implications for permafrost ecosystems and offers insights into effective fire management strategies.

The frequency of forest fires has increased dramatically due to climate change. The occurrence of forest fires affects the carbon and nitrogen cycles and react to climate change to form a positive feedback mechanism. These effects further impact the distribution of microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) and the soil microbial community structure. In addition, permafrost degradation can significantly affect the microorganisms in the soil. Based on these findings, this review examines the effects of fire intensity and post-fire recovery time on permafrost, the soil microbial community, MBC, MBN, and their interrelationships. This review demonstrated that (1) fires alter the condition of surface vegetation, reduce the organic layer thickness, redistribute snow, accelerate permafrost degradation, and even lead to permanent changes, where the restoration of the pre-fire state would require several decades or even centuries; (2) soil microbial community structure, soil MBC, and MBN negatively correlate with fire intensity, and the effects become more pronounced with increasing fire intensity; and (3) the structural diversity and stability of the soil microbial community were improved with time, and the amount of MBC and MBN increases as the years after a fire go by; it would still take more than ten years to recover to the pre-fire level. However, the relationship between permafrost degradation and soil microbes after forest fires is still unclear due to a lack of quantitative research on the mechanisms underlying the changes in soil microorganisms resulting from fire-induced permafrost degradation. Therefore, expanding quantitative studies and analyses of the mechanisms of interactions between forest fires, permafrost, and soil microorganisms can provide a scientific basis for understanding ecosystem carbon pools and dual-carbon targets in Arctic-boreal permafrost regions.