CARBON SEQUESTRATION POTENTIAL, VEGETATION STRUCTURE AND DIVERSITY OF GRAZING LANDS IN ABIJATA-SHALLA LAKE NATIONAL PARK, OROMIA REGIONAL STATE, ETHIOPIA

Abstract

This study aimed to assess the vegetation structures and the carbon sequestration potential, as well as the carbon stocks and soil properties of the ASLNP in Ethiopia. The random sampling techniques were used for species composition, vegetation structure, carbon pool and soil sampling. The two grazing intensities* 12 sampling site* five plots per sample site=120 sample were used. The woody DBH (>2cm) and height were used for vegetation structure and biomass estimation with allometric equation. The Smallian formula also used for the dead wood volume estimation. The soil samples were collected from three depths (0-10cm, 10-20cm and 20-30cm) of each plot and the composite was analyzed for physical and chemical properties. A total of 64 species, that belonged into 28 families were identified and recorded, whereas 24 were woody and 40 were herbaceous species. The height of woody vegetation ranges from 2m to 25m and classified into five classes as (2-5m, 5.1-10m, 10.1-15m, and 15.1-20m and 20.1-25m). In addition, the DBH also classified into six as (<10 cm, 10-20cm, 20-30cm, 30-40cm, 40-50cm and >50cm). The high proportions of (45.35%), woody species found in (10-20cm) DBH classes in the heavy grazed area and (38.78%) in the low grazed area. The densities of woody trees decrease as the height and the DBH increases. Furthermore, the herbaceous species has a significant variation (P<0.05) of species richness, diversity and evenness with grazing pressures. Furthermore, the overall mean carbon stock of aboveground, below ground, dead wood and litter were 112.3, 22.5, 6.9 and 0.95 t C ha-1, respectively. The soil physical properties (sand and silt) have significant change (P<0.05) with grazing intensities. The electric conductivity (EC), CEC, Ca+, Mg+ and Na+ showed the significance difference (P<0.05) with grazing pressure. Furthermore, pH, Av.p and OC have significance change (P<0.05) across soil depth. Generally, the overgrazing has negative impacts on the vegetation structure; biomass and the soil quality and due to this reason the carbon stock of the ecosystem was declined. Therefore, the sustainable management, such as destocking of livestock and intervention of community based conservation was suggested to sustain the ecosystem health and enhance the carbon sequestration potentials.