Post-fire effects on dissolved organic carbon concentrations in freshwater streams: a meta-analysis

• Following fire, DOC concentrations in streams increased 26 % during peak flow conditions. • DOC concentration increased during the early post-fire years, significantly during the second year. • Reporting DOC concentrations alongside discharge data, with a correlation index, would be highly informative. Wildfires alter hydrology and carbon export, yet the reported stream dissolved organic carbon (DOC) responses vary in magnitude and persistence. We conducted a meta -analysis of the peer-reviewed literature to assess wildfire effects on peak flow DOC concentrations in forested catchments (k = 52 effect sizes). A multi-level model showed a mean DOC increase of 26 % (95 % CI: 15–38 %), peaking in the second post-fire year (23 %) and attenuation thereafter. Responses varied with catchment and fire attributes. Small catchments (≤10 km 2 ) showed the largest increases. Humid continental climates exhibited strong increases, whereas subarctic sites tended to decline. Conifer-dominated forests increased more than mixed forests. Loam and clay loam soils showed substantial increases, sandy loam smaller but positive changes, and silt loam decreases. High and moderate severity, larger burned extent (10–50 % and >50 %), and short (<7 days) or long (>30 days) fire durations amplified early responses. Non-permafrost regions showed increases during the first years after fire. Two main mechanisms align with these patterns. Post-fire hydrology shifts reduce interception and infiltration while increasing near-surface runoff and enhancing hillslope-channel connectivity. Fire supplies labile residues that leach during storms. Event studies frequently report rising-limb enrichment and more chemodynamic behavior, which aligns with these mechanisms. Understanding DOC trajectories after fire informs ecosystem recovery, carbon budgets, and drinking-water treatment risk. Key gaps include the scarce discharge-resolved chemistry and a geographic skew toward North America. We recommend paired DOC-discharge sampling and standardized reporting to improve prediction of post-fire DOC export.