Abstract

Background: Humbo Farmer Managed Natural Regeneration (FMNR) forest is managed through direct involvement of the local community and funded by the World Vision Australia through World Vision Ethiopia under framework of the Kyoto Protocol’s Clean Development Mechanism on greenhouse gas emissions. Understanding the amount and distribution of carbon stored in forests across different elevations will enhance ability to anticipate how forests will react to future climate conditions and carbon levels. The aim of the study was to quantify the amount of carbon stocks along altitudinal gradients in the Humbo FMNR forest in southern Ethiopia. A total of 54 nested sample plots of 20 m × 20 m were established on transects of elevation gradients. Inventories of woody species and soil samples (0–10 cm and 10–20 cm depth) were collected within each nested sample plot. Carbon stocks in woody biomass and soil were compared by three elevation classes. Results: The total carbon stocks significantly (p < 0.05) differed among the three altitudinal gradients. There is no significant difference in biomass carbon stocks between the middle (1,610–1,750 m above sea level [a.s.l.]) and lower (1,470–1,610 m a.s.l.) elevations. However, both of these elevations significantly differ (p < 0.05) from the higher (1,750–1,890 m a.s.l.) elevation, despite an increase in carbon stocks from lower to higher elevations. The highest ecosystem carbon stock was contributed by soil carbon. The higher proportion of C stocks at the higher elevations may be associated to the species composition and dominance with larger wood density. Conclusions: It was concluded that even though soil carbon contributed higher carbon to the total carbon stock, biomass is stronger impact than soil carbon when it comes to carbon stock variation by altitudinal gradients. We recommend that carbon-related awareness creation on reducing emission for the local people and promotion of knowledge on carbon stock credits accounting and to be claimed in future for financing, which could be considered as additional possible option for sustainable forest management.