Above- and belowground biomass and biomass carbon stocks in homegarden agroforestry systems of different age groups at three sites of southern and southwestern Ethiopia

Abstract

Abstract As the loss of forests over time results in a net flux of carbon (C) into the atmosphere, the practice of agroforestry can combat this and serve as a long-term sink for CO2. Based on the inventory of 93 homegarden agroforestry systems (AFS) in three study sites and using a non-destructive method involving allometric equations, the research assessed aboveground (AG) and belowground (BG) biomass and biomass C stocks across sites and along age groups in homegarden AFS in southern and southwestern Ethiopia. Plant diversity parameters were also gathered on perennial plant species. Results indicate that the mean perennial plant species richness per homegarden agroforestry, and other diversity parameters varied strongly among sites (p < 0.05). Biomass C stocks range from 18.11 at Malo Ezo to 32.86 Mg C ha−1 at Saja Laften for AG, 3.97 to 7.10 Mg C ha−1 for BG, and 22.02 to 39.96 Mg C ha−1, for each respective sites, for the overall biomass C stocks were recorded within the homegarden agroforestry systems. In terms of age groups, the mean total biomass C stock did show numerical change from the initial, ≤10 years (22.49 Mg C ha−1) to the middle age group, >10 and ≤20 years (39.96 Mg C ha−1), but it was stagnant 20 years onward (28.49 Mg C ha−1). The homegarden agroforestry systems had the potential to store up to 80.81–112.30 Mg·ha−1 of CO2 equivalents across sites, and 82.53–104.55 Mg·ha−1 of CO2 equivalents along age groups. A positive relationship was noted between AG woody biomass C stocks and attributes such as woody species richness, and woody plant density. Considering the involvement of large numbers of homegardeners, future improvements and expansion of homegarden agroforestry to larger areas can enhance to a great extent the potential to sequester C and thereby mitigate climate change.