WOODY SPECIES DIVERSITY AND CARBON STOCK IN HOMEGARDEN AGROFORESTRY PRACTICE IN METU DISTRICT OF ILU ABA BOR ZONE, SOUTHWESTERN ETHIOPIA

Abstract

Homegarden agroforestry practices encompass an assortment of woody species and provide a number of social, ecosystem services and economical benefits. Many studies have been undertaken to identify woody species and quantify the carbon stock potential of homegarden agroforestry. However, there is still little focus on the relationship between woody species diversity and carbon stocks. This study was aimed at assessing woody species diversity and carbon stock and the relationship between woody species diversity and carbon stock of homegarden in Metu District, Southwest Ethiopia. Metu District was purposively selected based on the presence of homegardens agroforestry practices and the researcher's familiarity with the area. Accordingly, three Kebeles, namely, Ale Buya, Serdo, and Beroye Gebisa were identified. A nested quadrat size of 20 m x 20 m, 5 m x 5m, and 1 m x 1m were used for trees, shrubs, and samplings, and soil samples respectively. All woody species, both fruit and non-fruit trees, with a DBH ≥2.5 cm and a height ≥1.5 m were identified, measured, and documented in 45 plots. The diameter of the coffee shrubs was measured at stump height (40 cm). Ninety composite and ninety undisturbed soil samples were taken for Soil organic carbon and bulk density analysis, respectively. To quantify biomass carbon stock, an allometric equation was used. A total of 47 woody species belonging to 28 families were found in the 45 quadrates of the study area. The average H’ and evenness of woody species were 1.80 and 0.81, respectively. There were significant differences (P <0.05) in the diversity indices. The average bulk density and Organic Carbon% of the soil were 1.16 and 1.21 g cm-3, and 2.14 and 1.08% for (0–30 cm) and (30 – 60 cm) depth, respectively. The overall mean Biomass Carbon, Soil Organic Carbon, and Total Carbon were 49.25, 169.86, and 219.11±49.13 Mgha-1 respectively. Soil organic carbon stocks comprised 77.5% of the total carbon stock. In general, the homegarden agroforestry practices of Metu District, Southwest Ethiopia, had a high contribution to woody species conservation and carbon stocks. To improve species composition of villages and kebeles with lower values, the attintion of different stakeholder is important.The high carbon stock in the homegarden agroforestry system of the study area has substancial contribution for mitigation of greenhouse gasses.