Abstract
Ethiopian tropical forests present a great geographical diversity with high and rugged mountains, flat-topped plateaus, deep gorges, river valleys, and plains and as a result, it has different species diversity, biomass, and soil carbon stock. The study was conducted in a Kua-Chalte moist Afromontane natural forest located in Limmu Seka Woreda, Jimma Zone, Oromia Regional State, and Southwest Ethiopia. The aim of the study was to assess the woody species composition, diversity, structure and to determine carbon stocks of the forest.
A total of 60 plots, each within 20m × 20m were laid systematically at 100m interval along the altitude and aspect to collect vegetation and soil data. In each of the plots, all woody species were recorded; cover-abundance of woody species estimated, and their height and DBH were measured. Five subplots, each with 1m × 1m were laid at the four corners of the main plots for collecting composite soil samples and the middle of each plot for bulk density analysis. Similarly, four subplots of 1m × 1m were laid at the four corners of each plot to collect litter data. A total of 67 woody tree species belonging to 35 families and 56 genera was recorded and identified. The most dominant families were Fabaceae, followed by Moraceae, Oleaceae, Asteraceae, Rubiaceae, and Rutaceae respectively. The total basal area and IVI of the forest were 48.17 m2/ha and 300.01respectively. Forests play an important role in keeping the greenhouse effect and carbon cycle working naturally by reducing CO2 emissions and increasing the CO2 pulled out of the atmosphere and stored as carbon that helps for climate change mitigation. With this importance, altitude and aspect affect the carbon sock of the study area. The mean above and below ground carbons was increased as altitude increase, whereas carbon along aspects was not statistically significant. The other pools of carbons were showing an increasing or decreasing pattern along with altitude, while soil organic carbons along lower, middle and high altitude resulted in 162.02, 216.77 and 190.72 t/ha respectively, and SOC along aspect was 133.53, 172.61, 152.67 and 169.61 t/ha within the respective direction of W, S, N, and E independently.
Keywords: Altitude, Aspect, Kura-Chalte natural forest, Biomass carbon, Floristic composition, and Soil carbon.