Fire is a key ecological driver in savanna systems, influencing soil biogeochemical processes by releasing nutrients but also causing potential losses through volatilization and leaching. In this study, we investigated how fire seasonality and soil depth influence both Mehlich-3 extractable nutrients and total elemental concentrations. This study was conducted in a long-term fire experiment consisting of 20 plots subjected to seasonal burning treatments (dry season, late dry season, late wet season, and an unburned control). Soil samples were collected from two different depth horizons (0–15 cm and 15–30 cm) and analyzed for nutrient concentrations. We used two-way PERMANOVA, Scheirer–Ray–Hare tests, and non-metric multidimensional scaling (NMDS) to assess treatment effects and interactions. Results showed that fire seasonality did not significantly affect Mehlich-3 extractable nutrients; in contrast, soil depth strongly structured nutrient profiles, with higher concentrations in the upper soil layer, while total elemental concentrations were consistently enriched in the deeper soil horizon. Fire seasonality influenced total elemental nutrient pools, with late dry season burns enhancing potassium and other cations, likely due to combustion of accumulated dry biomass and subsequent ash deposition. Depth effects were particularly pronounced for TN and OC, which were elevated in deeper layers due to the presence of mineral-associated organic matter OM. Our findings highlight that vertical stratification is the dominant control of nutrient distribution, while fire seasonality modulates specific nutrient dynamics. These results underscore the need to incorporate soil profile depth and fire timing when evaluating post-fire soil fertility and ecosystem resilience in savanna landscapes.
Kasinda et al. (Tue,) studied this question.