Variations in Forest Carbon Stocks Along Environmental Gradients in Egdu Forest of Oromia Region, Ethiopia: Implications for Sustainable Forest Management

Abstract

Forests play a significant role in climate change mitigation by sequestering and storing more carbon from the atmosphere than any other terrestrial ecosystem. Although a number of studies have been done on carbon stock estimations, the influence of environmental factors on forest carbon stocks has not been properly addressed. This study was conducted to estimate the carbon stock and its variation along the altitudinal gradients in Egdu dry afromontane forest found in Oromia Regional State of Ethiopia. The carbon stock in the different carbon pools and analysis of the influence of the environmental variables were studied by collecting data in sixty-nine quadrat plots of 10 x 20 m distributed along transect lines. To estimate carbon in above and below ground biomass; each tree in the study site having diameter at breast height (DBH) of ≥ 5 cm were measured for DBH and height. Above ground biomass was estimated by using allometric model while below ground biomass was determined based on the ratio of below ground biomass to above ground biomass factors. The mean total carbon stock density of Egdu Forest was found to be 614.72 ± 35.79 t ha-1 (ranging from 182.6 to1416 t ha-1), of which 45.24% of carbon was contained in the above ground biomass, 9.05% in below ground biomass, 0.56% in litter carbon and 45.15% was stored in soil organic carbon (0-30 cm depth). The carbon stocks in above ground biomass, below ground biomass, litter biomass and soil organic carbon exhibited distinct patterns along environmental gradients (slope gradient and slope aspect). The analysis of carbon stock variation of different carbon pools on eight different aspects of the forest area showed a significant variation with exception of soil organic carbon stock. The amount of carbon stock in above and below ground biomass, soil organic carbon and the total carbon stock was higher on the northern aspect as compared to other aspects. On the other hand, the carbon density of the forest carbon pool components showed a negative correlation with slope gradient; with increasing % slope, the above and below ground carbon, soil organic carbon and the total carbon stock decreased. This study concluded that the carbon stock value of Egdu Forest is large, and the carbon storage in different carbon pools of the forest area varies with slope aspect and slope aspect.