Abstract
A comparative assessment of carbon stocks of natural and plantation forests in Setema district, Jimma zone South West Ethiopia was conducted. Carbon (C) densities of the biomass and soil (0–40 cm) in the natural forest and plantations of Eucalyptus and C. lusitanica in the Setema forest were determined and compared. In the stratum or forest stand, sample plots of 20 m x 20 m,(square) were randomly laid to measure the biomass of woody plants, a total of 90 (30 in each stratum) sample plots were taken for C stock inventory.
Biomass C densities were estimated from total tree height, breast height diameter, and wood density using allometric functions developed for tropical species and an assumed C content of 50%. Belowground biomass C densities were estimated using root: shoot biomass ratios. Soil organic C (SOC) densities were calculated from measured organic carbon contents (0–20 and 20–40 cm layers) and modeled bulk density values. Mean total biomass C densities for natural forest were greater than those of the plantations, and mean total SOC densities for plantations were greater than those of the natural forest, and the difference was significant (p < 0.05) in the cases of plantation and natural forest, but not significant in SOC in the case of E. globulus plantation species. Natural forests can store more total C stocks than plantations of exotic species, but the difference between natural forests and plantation of exotic was depended on plantation species. Therefore, species selection is vital when establishing tree plantations with the aim of the restoration of degraded soils and biomass carbon stocks. Conservation of the natural forest will have an imperative implication to the total C density and ensuring its viability.
Keywords: biomass; carbon stocks; C. lusitanica; E. globulus; natural forest; soil carbon stocks
