Pathways of Litter Decomposition, Nutrient Dynamics and Carbon Stock Mapping in Asabot Dry Afromontane Forest: Implications for Sustainable Management of Ecosystem Functions and Services Tulu Tolla Tura Addis Ababa University, 2018 This study was aimed at assessing and understanding the dry Afromontane forest ecosystem functioning by analyzing the pathways of biomass decomposition, plant community formations and nutrient dynamics in the mountainous landscape of the Asabot forest in the eastern highlands of Ethiopia. The plant community groups were studied using a systematic sampling method. For the biomass decomposition study, litter bag experimental plots were established along the altitudinal gradient of the upper, middle and lower elevations of the landscape. A total of 660 litterbags were buried in ten experimental plots (66 in each plot) in the top soil of the forest floor. Every five of the bags were collected in each month in order to examine the weight loss, decay rate, decay constant and the nutrient dynamics. The microbial communities in the litter bag experimental plots were studied by collecting soil samples from each plot during the wet seasons. The soil microbial community biomass was estimated using ester linked fatty acid methyl ester (EL-FAME) and the respiration rate was estimated by trapping the carbon released with the CO2 and the soil microbial activity was estimated by measuring the β-glucosidase enzyme activity in the soil samples. The study identified about 97 plant species distributed among 90 genera and 52 families in the Asabot dry Afromontane forest. Three plant community groups were identified according to hierarchical dendrogram analysis. Moreover, eight specific and three general trends of population structure are observed along with trees and shrub dominance. The microbial analysis identified 57 EL-FAMEs biomarkers associated with soil microbial community. The identified biomarkers biomass abundance (nmole g-1 soil) related with hydrocarbons in descending order are saturated (278.37)>unsaturated (187.77)> cyclic and OH (20.82)>branched (14.69), respectively. The microbial community biomass abundance was negatively correlated with altitude gradients; as altitude increases microbial community biomass abundance decreases. The biotic and abiotic environmental factors correlation with soil microbial community abundance is found to be significant (p<0.05). Moreover, the correlation of the soil microbial community respiration and β –Glucosidase enzyme activity with that of biotic and abiotic environmental factors is found to be significant (p = 2x10-16). Averages of the monthly and yearly decay constant (k) are found to be 0.081 and 0,97, respectively. Fifty percent (50%), ninety-five percent (95%), ninety-nine percent (99%), of the time of the initial leaf litter mass loss of the decay constant (k) range from 0.59 to 0.84 year, 2.55 to 3.62 years and 4.22 to 6.04 years, respectively. The litter residues nutrient dynamics linearly decreases as experimental days increases with the exception of nitrogen, which showed increasing trends. Litter nutrient shows change of 44.1 % on average during the first 120 to 360 days of the experiment with noticeable variation between altitude gradients and within altitude gradients. The soil nutrient dynamics was observed to generally exhibit an exponential trend. Correlation of the microbial biomass abundance and activity with litter decomposition and nutrient dynamics is found to be significant (p<0.05). The study has revealed that, the litter decomposition and nutrient dynamics of dry Afromontane forest are significantly influenced by biotic and abiotic environmental factors variability along altitude gradient. Moreover, the study showed that the potential candidacy of dry Afromontane forest in climate change mitigation and carbon trade negotiation. In conclusion, a well-maintained plant community interaction with soil microbial community, microbial community response for biotic and abiotic environmental factors, and litter decomposition and nutrient dynamics response for biotic and abiotic environmental factors observed to positively influence dry Afromontane forest ecosystem functions and services in a changing climate.