Above ground biomass and carbon stock estimation of Gmelina arborea (Roxb.) stands in Omo Forest Reserve, Nigeria

Abstract

Above ground biomass and carbon stock were estimated for Gmelina arborea plantations (34, 32, 30, 26, 24, 22, 20, 18 and 16 years old) in Area J4 of Omo Forest Reserve, Nigeria. A total of 45 plots (20 x 20m) were laid (5 plots in each age series) and growth data were collected from a total of 8816 trees. Two trees from each plot were randomly selected and wood core samples were collected and analyzed for wood density. Volume over bark (VoB), total above ground biomass (TAB) and carbon stock (CS) were estimated. The results were subjected to descriptive statistics. The result reveals number of tree stands per hectare ranges from 875 to 1000 while basal area and VoB had respective values which ranges from 33.31±0.034 to 413.78±0.074 m²/ha and 297.14±0.044 to 6375.21±0.121 m³/ha. The mean TAB ranges from 5246.93t/ha (34 years old) to 266.80t/ha (18 years old). In the same trend, the mean CS estimated was highest in 34 years old stands (2623.46t/ha) while the least was observed in 18 years old stands (133.40t/ha). The result shows that there is a significant relationship between the dbh and TAB (0.955) hence, as the dbh increases the TAB increases. This is the same for dbh and CS (0.955). Gmelina has a high biomass yield per hectare, even at young age. The high stem biomass also indicates that a high proportion of Gmelina wood is merchantable for timber. Conceptually trees are considered to be a terrestrial carbon sink. Therefore, managed forests can, theoretically, sequester carbon both in situ (biomass and soil) and ex situ (products).

Keywords: Above ground biomass, carbon stock, Gmelina arborea, growth and management