Non-linear models for tree volume and above ground biomass estimation in Afi River Forest Reserve, Cross River State, Nigeria

Abstract

The research aimed at developing non-linear models for tree volume and aboveground biomass estimation in Afi River Forest of Cross River State, Nigeria. Two transects of 1500m in length with a distance of 500m between the two parallel transects were used for this study. Sample plots of 50m X 50m in size were laid in alternate along each transect at 100m interval and thus, summing up to 10 sample plots per 1500m transect and a total of 20 sample plots in the study area. A total of 1368 individual tree species spread across 23 species belonging to 18 different tree families were measured for diameter at breast height, diameters at the base, middle and top and tree total height. The mean diameter at breast height (dbh) and total height of 25.8cm and 18.5m were respectively obtained while12.01 m3 and 80.72 kg were obtained for average tree volume and biomass respectively. At stand level, mean basal area of 48.95m2ha-1 was obtained with a mean volume of 244.561m3 ha-1and mean green biomass was 448.860ton ha-1with a dry biomass of 325.423ton ha-1. Curve Expert software was used for model’s development. For tree volume estimation, Weibull model was the most flexible, however, Logistic models and Gompertz Relation models were most flexible for aboveground biomass estimation based on the assessment criteria (AIC and standard error) and therefore recommended as the best fit models for individual tree volume and aboveground biomass estimation in the study area.