2025/09/23 by Zhenhui Jiang, Olga Ogneva, Yakov Kuzyakov +5 · 1 voice
Environmental Science · Agricultural and Biological Sciences · #Fire effects on ecosystems #Soil Carbon and Nitrogen Dynamics #Atmospheric and Environmental Gas Dynamics
paper · doi:10.1016/j.soilbio.2025.109986
openalex publication_date 2025/09/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/02
Frequent burning and its induced dry–wet cycles pose increasing threats to soil organic matter (SOM) stability. Yet, their interactive effects on microbial-driven decomposition and priming remain unclear from the combined perspectives of CO 2 emissions and energy (i.e., heat) release. The relationship between microbial substrate use efficiency (SUE) and the calorespirometric ratio (CR, heat-to-CO 2 ) remains unclear. Here, we investigated how long-term prescribed burning over 46 years, applied at two- (B2) and four-year (B4) intervals, interacts with dry–wet cycles (defined as cycles of soil drying and rewetting that reflect fire-induced moisture fluctuations) to influence SOM decomposition. Using the addition of 14 C-labeled glucose coupled with calorespirometry, we tracked SOM-derived CO 2 and heat fluxes and quantified the priming effect during a 28-day microcosm experiment. B4 increased SOM-derived CO 2 efflux and heat release vs. unburned soils (NB), while B2 suppressed both. Dry–wet cycles increased SOM-derived CO 2 but reduced SUE, favoring respiration over biomass synthesis. B4 under wet conditions produced higher primed heat than NB, which was linked to the use of a chemically complex substrate (indicated by elevated CR). The decoupled primed CO 2 -heat indicated distinct thermodynamic pathways for carbon (C) and energy release. A positive CR–SUE correlation revealed a metabolic coordination between energy dissipation and C assimilation, suggesting that microbes allocate additional energy to sustain biomass growth even under elevated energetic costs. These findings demonstrate that low-frequency burning accelerated C loss via energy-intensive decomposition, while dry–wet cycles increased soil C vulnerability by uncoupling microbial growth and respiration. Integrating C and energy flux metrics provides novel insights into soil C resilience under compounding climate disturbances, urging balanced fire management and C conservation in vulnerable ecosystems. • Low-frequency burning enhanced SOM-derived CO 2 emissions and heat release • Dry–wet cycles intensified microbial CO 2 flux and heat dissipation • Burning enhanced priming effects on CO 2 and heat; rewetting suppressed primed heat • Positive CR–SUE correlation reveals microbial energy–carbon coordination