WOODY SPECIES DIVERSITY, MANAGEMENT, AND CARBON STOCKS OF PARKLAND AGROFORESTRY PRACTICES, IN NEGELLE ARSI, CENTRAL RIFT VALLEY, ETHIOPIA

Abstract

Agroforestry consists different diversity of plants and has a unique potential of balancing the net carbon emissions as a sink and reservoir for CO2 at both above and below-ground. The objective of this study was to investigate woody species diversity, management, and the biomass carbon and soil organic carbon stocks of Parkland Agroforestry (PLA) in Nagelle Arsi, Central Rift Valley of Ethiopia. Three study kebeles (Aliwoyo, Ashoka and, Godeduro) representing lowland, midland and highland agroecological zones were selected purposively. For woody species inventory, plot size of 500 m2 ( 50 m x 100 m) was used and data was collected from a total of 30 plots in the crop fields. Woody species found in the plots with DBH ≥ 5 cm were recorded using a diameter tape. Soil samples were taken from four corners at different depth range (0- 20cm, 20-50cm, 50-80cm and 80-110cm) using an auger. Hence, 120 composite soil samples and similar size of undisturbed soil sample were taken for organic carbon and bulk density determination using a 6cm*6cm core sampler. A questionnaire was developed and information was gathered on management strategy of woody species and analyzed using SPSS version 20 . The diversity of woody species was analyzed by using diversity indices while Biomass carbon was estimated using allometric equations. A total of 28 woody species belonging to 17 families and 15 genera were gathered, identified, and recorded. Of these, 8 woody species were recorded in lowland and 20 woody species were recorded in midland and highland. The highest diversity was recorded at highland while the highest evenness was recorded at midland. The total woody biomass and biomass carbon of highland Parkland agroforestry practices was considerably higher (17.57ton/ha) and (8.43ton/ha) than at midland and lowland parkland agroforestry (14.96ton/ha) and (7.18ton/ha), 9.39ton/ha and 4.50ton/ha, respectively. Similarly, the total soil organic carbon of highland was considerably higher (103ton /ha) than midland and lowland parkland agroforestry which was 92ton/ha and 72ton/ha, respectively. The total mean carbon stock for biomass and SOC stock were 20.11 and 35.80 ton / ha, respectively. Farmers retain and/or plant woody species in their parklands for the purpose of fuel-wood, construction, fodder, shade, soil conservation, and medicine. The management employed in the study included pruning, lopping, protecting, pollarding,and coppicing of woody species. Generally, the study indicated that Parkland agroforestry practices could be considered as an option to halt loss of diversity, to build local level adaptive capacity and contribute to mitigating the negative impacts of climate change through reducing carbon emission . In-depth assessment of Agroferstry systems is important to quatify the status of native woody species in the area