Tree species diversity, soil physicochemical, biomass and carbon stock assessment in Guyaku grazing reserve, Gombi Lga, Adamawa State.

Abstract

Forests provide a variety of products and services to human societies, sustain diverse flora and fauna, and, through their interception and processing of solar energy and precipitation, influence climate and the composition of the atmosphere. Deforestation and degradation of forests lead to the emission of carbon dioxide through the burning of forest biomass and the decomposition of plant parts, soil carbon, which accelerates and contributes to a long-term rise in atmospheric carbon dioxide levels. This research aimed at determining tree species diversity, soil physicochemical, biomass and carbon stock assessment in Guyaku grazing reserve. Systematic line transects were employed in the laying of the plots. Two parallel transects of 1500m in length with a distance of 500m between the two parallel transects in the grazing reserves. Sample plots of 50m x 50m in size were laid in alternate rows along each transect at 100m intervals, with 4 sample plots per 1500m transect, totalling 8 sample plots. In each sample plot, all living trees with dbh ≥10cm were identified and measured for diameter at the base, middle and top and total height. Diameter tape/girth and Spiegel relaskop were used for tree height and diameter at the base, middle, top and dbh measurement. Soil samples were taken from four soil depths of 0 – 15cm, 16 – 30cm, 31 – 45cm and 46 – 60cm at three points (i.e. at the two edges and middle of the line). One-way analysis of variance (ANOVA) and Student t-test of significance was used to determine the difference in each soil nutrient according to depth, tree density, species diversity and richness, basal area and bio – volume of the six grazing reserves. Results show that 13 species, 6 families, 86 species/plot and 43 nha-1. Total Ba/ha 0.38cm and 4.39m³ vol/ha. The Fabaceae family has the highest frequency 30 while unknown and moraceae lowest with 7 and 8, respectively. Dbh and height class range 0-10 to 41-50 and <11 to 21-30, respectively. Total biomass, carbon stock and CO2 (5.70ton/ha, 2.85ton/ha and 10.45kg) respectively. Textural classes are sandy loam and sandy clay loam. Physical properties revealed sand 65.58±8.55% higher than silt and clay. Total bulk density 1.52±0.08g/cm³, lower than particle density 2.63±0.23glcm³. Porosity at 41.39±8.05%, while WHC at 19.74±3.08% moderate. Chemical properties showed that P^H 6.52±0.33 is slightly alkaline, EC at 0.07±0.05ds/m. Organic matter 2.15±0.24% higher than OC and TN. Av-p at 9.10±0.74mg/kg. ECEC at 7.64±1.47cmol/kg is higher than Ca, Mg, Na, K, H, AI, TEB, TEA. PBS at 83.52±3.97% higher than ESP at 7.57±2.68%. The findings revealed that porous soils slightly improve growth, with soil structure and mineral density playing roles in dominant tree development. Furthermore, growth traits are moderate to strong and positive, showing good structural consistency. It is recommended that strengthening protection and sustainable management of forest and grazing reserves minimise biodiversity loss and implement comprehensive soil protection strategies.