Winter wildfire effects on soil properties in semiarid Mediterranean scrubland and pine forest

Wildfires are increasingly occurring outside the traditional summer season in Mediterranean regions, driven by climate change and altered fire regimes. However, the ecological consequences of winter fires remain poorly understood, particularly in semi-arid ecosystems where soil properties are critical for post-fire recovery. This study evaluates the short-term effects of a winter wildfire on physical, chemical and biochemical properties of the 0–5 cm mineral soil layer, sampled after removing ash and loose charred litter, in two contrasting ecosystems, scrubland and Aleppo pine forest, located in southeastern Spain. Burn severity was assessed using field-based BAER protocols and classified into unburned, moderate, and high severity classes. Soil samples were collected one and ten months after the fire to analyze pH, electrical conductivity, organic carbon, nitrogen, available phosphorus, water retention, enzymatic activities, basal soil respiration, carbohydrates and polyphenols. Results indicate that winter wildfire caused substantial changes in surface conditions, reducing vegetation cover and increasing ash deposition, while effects on the sampled mineral soil properties were moderate. Significant variations were observed in pH and electrical conductivity, whereas organic carbon, nitrogen, and most enzymatic activities remained largely unaffected, particularly in pine forest soils. Carbohydrates increased over time in both ecosystems, while whereas polyphenols showed a mainly temporal increase. Multivariate analyses revealed that severity effects were more evident in scrubland than in pine forest, and recovery trajectories were influenced by vegetation structure and water availability. These findings suggest that winter wildfires, despite high apparent severity at the surface, may exert relatively limited effects on the upper mineral soil under the conditions studied, a pattern consistent with the cool and wet-season context of the fire . Rather than providing direct support for prescribed winter burning, these results may help inform future experimental evaluations and adaptive fire management strategies in Mediterranean semiarid landscapes under changing climate conditions.