Activities of soil carbon and nitrogen enzymes during charcoal production in derived savanna of Nigeria

Abstract

Abstract In recent years, anthropogenic activities, particularly charcoal production and the extensive use of large fuelwoods have significantly compromised the deforestation of savanna forest soils in southwestern Nigeria, with notable impact on soil enzymes and nutrient cycles. Despite the growing recognition of charcoal’s influence on soil properties, there is a noteworthy gap in the literature regarding its specific effects on soil carbon (C) and nitrogen (N) enzymes. To address this gap, our study aims to examine the impact of charcoal production on the C and N enzymes activities, under different locations and soil depths in the derived savanna of southwestern Nigeria. Soil samples were systematically collected and analyzed at depths of 0–15, 15–30, and 30–45 cm from charcoal production sites (CPS) and non-production sites (NPS). The result showed significantly higher activity levels for amylase (0.54 µg/ml/min) and cellulase (0.90 µg /ml/min) at the NPS compared to CPS. In contrast, protease and urease activity were higher at CPS (0.54 and 16.66 mg/ml/min respectively) than at NPS, suggesting distinct protein degradation patterns at both sites. The amylase/cellulase activity ratio was greater at CPS than NPS, with no significant difference between values (1.44 and 0.79 µg/ml/min, respectively). Similarly, the protease/urease activity ratio was identical at both sites (0.04 mg/ml/min). However, this ratio decreased with depth due to heightened protease and urease activities, which catalyzed the mineralization of organic nitrogen, resulting in increased nitrogen content and the release of ammonia-N in soils. Overall, our findings suggest that charcoal production may influence and alter soil enzyme activities, potentially impacting the breakdown of carbohydrates, cellulose, proteins, and urea in the soil. These variations in enzyme activities could have broader implications for nutrient cycling, microbial processes, and overall soil health in areas with charcoal production areas compared to non-production sites. Article highlights C and N enzyme activities were higher at NPS in rèle. The protease recorded the highest at CPS in Òkè-Àkò, it ranked lowest among enzymes at NPS. Significantly higher C enzyme activity was recorded in 30–45 cm soil depth at NPS. However, the N enzyme was higher at 0–15 cm at CPS. Amylase/cellulose activity increased with increasing soil depth at both sites. In contrast, protease/urease decreased with depth.