Floristic Composition, Structure and Biomass Carbon Stock Estimation of Parkland Agroforestry Woody Plant Species in Midland and Lowland of Doha Kebele, Kena District, Konso Zone, South Ethiopia

Abstract

Floristic, structure and biomass of carbon storage estimates of parkland agroforestry have not been received much attention. This study investigated the woody species composition, diversity, structure, and carbon stock of parkland agroforestry systems in Doha kebele Kena district Konso zone, South Ethiopia. A systematic sampling method was applied to locate the sample plots to collect woody species structure and composition. Six transects (Midland: 4; Lowland: 2) were established 300m apart from each other along altitudinal gradient. Forty-one (30 in midland and 11 in low land) plots (30m x 30m) were laid along transects with 150m apart between the plots. Trees and shrubs were counted in each plot. The DBH/DSH and height of trees/shrubs with DBH/DSH ≥ 5cm was measured. Descriptive statistics were used to analyze the data. Two-sample t-test was used to compare a statistical difference between the means of lowland and highland agroecologies. A total of, 28 agroforestry plant species (23 genera and 19 families) were identified in the study area (Midland: 24 species; Lowland: 14 species). Out of this, 14 were exclusive to the midland; 4 were found only in the lowland agroforestry, 10 being common to both. Moraceae and Anacardiaceae were the most dominant families. The study indicated that the woody species Shannon and Simpson diversity indices were higher at midland than lowland agro-ecology. A Sorensen’s similarity between the two agro-ecological agroforestry was 52.6%. In the midland, the most frequent species were Juniperus procera, Terminalia brownii, Catha edulis, Ficus sur and Cordia africana. In the lowland, the most frequent species were T. brownii, Moringa stenopetala, Grewia bicolor and Sterculia africana. Overall, 642 individual species were collected from 3.69ha from the two agro-ecological zones. The density of woody species in lowland was lower (135.353 stemha-1) than midland agroforestry (188.1481stemha-1). The mean basal area of midland (2.58m2) was higher than the lowland agroforestry (0.3m2). In midland, the top five ranked woody species were J. procera, T. brownii, C. edulis, C. africana and F. sur with the IVI value of 83.9, 44.64.61, 12.2, 10.25, and 8.9, respectively. In the lowland agroforestry, T. brownii, M. stenopetala, S. africana, G. bicolor, and F. ovate were the top five ranked species with the IVI value of 119.35, 48.67, 8.82, 8.85, 4.85, respectively. The total biomass and the biomass carbon of midland was considerably higher (141268.2Kg) and (70634.1Kg) than at lowland agroforestry (7627.6Kg) and (3813.9Kg), respectively. Promoting agroforestry systems is found to be useful for climate change mitigation.