Carbon stock and woody species diversity in homegarden agroforestry along an elevation gradient in southern Ethiopia

Agroforestry practices that integrate trees into farming are known to enhance carbon sequestration and plant species diversity in agricultural landscapes. Their contribution however, varies depending on a number of factors including elevation gradients. In this study, we quantified the carbon (C) stock and woody species diversity in tree-ensete dominated homegarden agroforestry practice along an elevation gradient in Hawassa Zuria District, southern Ethiopia. The elevation was stratified into upper, middle and lower gradient and two hamlets were randomly selected from each elevation category. Data on number, diameter and height of woody species were collected from 42 sample home gardens. Soil samples were also taken at 0-60 cm soil depth from each sample home garden for soil organic carbon (SOC) determination. A total of 49 woody species belonging to 31 families were recorded. The diversity differed significantly (p < 0.05) along the elevation categories. The mean total biomass and soil carbon stocks were significantly (p = 0.001) higher in the upper elevation category (156.17 +/- 13.78 Mg ha(-1)), followed by middle (128.66 +/- 7.16 Mg ha(-1)) and lower (91.75 +/- 4.31 Mg ha(-1)) elevation categories. The corresponding SOC accounted for 68%, 76% and 78%. Correlation between woody species diversity and C stock was not significant (r = - 0.16). The tree-ensete dominated home garden agroforestry practices can play an important role in climate change mitigation and conservation of woody species diversity. The carbon accumulation potential of agroforestry systems vary along elevation gradients, but not necessary due to differences in woody species diversity.