Multi-Indicator Assessment of Short-Term Forest-Soil Responses to the 2026 Wildfire Period Using Paired Field Observations and Regional GIS Analysis

Wildfires can rapidly alter soil physicochemical and biological properties, but short-term paired field evidence from North African forests remains limited. We assessed changes in 14 soil indicators at ten forest sites in northeastern Algeria and interpreted these field observations within a regional GIS analysis of Mediterranean wildfire exposure. The same locations were sampled in March 2026, before the seasonal fire period, and revisited in August 2026. The measured variables comprised soil pH, electrical conductivity (EC), soil organic carbon (SOC), total nitrogen (TN), available phosphorus (P), C:N ratio, microbial biomass carbon (MBC), basal respiration, dehydrogenase activity (DHA), MBC:SOC ratio, gravimetric soil moisture, bulk density, water-stable aggregates, and surface litter biomass. Within-site changes were evaluated using exact paired Wilcoxon tests with Holm correction and paired-bootstrap confidence intervals. Across the ten sites, pH increased by 0.60 units, EC by 112.9%, and available P by 79.6%. In contrast, SOC, TN, MBC, basal respiration, soil moisture, water-stable aggregates, and litter biomass decreased by 26.7%, 36.8%, 49.4%, 44.2%, 40.5%, 37.1%, and 71.0%, respectively. Bulk density and C:N increased by 11.2% and 11.3%, while DHA increased by 29.8%. All 14 paired comparisons remained significant after Holm adjustment (adjusted p = 0.027). PCA accounted for 96.2% of the total variance and separated the March and August profiles. At the regional scale, the complementary EFFIS analysis identified 800,540 ha of mapped wildfire exposure through 6 August 2026, with substantial concentration in Spain, Algeria, France, Italy, and Portugal. Collectively, the paired observations indicate a post-fire-period shift characterized by an ash-associated increase in soluble ions and available phosphorus alongside losses of organic matter, microbial biomass, moisture, aggregate stability, and surface litter. Because contemporaneous unburned control plots and independent plot-level burn-severity measurements were unavailable, the observed changes cannot be attributed exclusively to wildfire and may also reflect seasonal environmental variation.