Phytosociological, Soil Physicochemical, and Carbon Stock Assessment in Jibiro Grazing Reserve Girie Local Government Area, Adamawa State, Nigeria

Abstract

This study assessed the phytosociological characteristics, soil physicochemical properties, and carbon stock of Jibiro Grazing Reserve. A systematic line transect design was used, consisting of two parallel transects (1500 m each) spaced 500 m apart. Along each transect, four 50 m × 50 m sample plots were established alternately at 100 m intervals, resulting in eight plots. All living trees with diameter at breast height (DBH) ≥10 cm were identified and measured for DBH, basal diameter, and total height. Soil samples were collected from three points per plot at depths of 0–15, 16–30, 31–45, and 46–60 cm. Data were analysed using one-way ANOVA and Student’s t-test. A total of 12 tree species belonging to 7 families and 68 individuals were recorded, with a stand density of 34 trees ha⁻¹. Phyllanthaceae had the highest frequency, while Sapotaceae was least represented. Total basal area and tree volume were 0.22 m² ha⁻¹ and 1.63 m³ ha⁻¹, respectively. Diameter classes ranged from 0–50 cm, and height classes ranged from <11 m to 20 m. Estimated biomass, carbon stock, and CO₂ equivalents were 3.10 t ha⁻¹, 1.55 t ha⁻¹, and 5.68 kg, respectively. Soils were predominantly sandy loam to sandy clay loam, with high sand content (67.25%). Bulk density was lower than particle density, while porosity (39.10%) and water-holding capacity (13.00%) were low. The soil was slightly acidic (pH 7.14), with moderate organic matter and available phosphorus, and high base saturation (79.25%), indicating nutrient limitations affecting vegetation growth.