Carbon stocks vary in reference to the models used, socioecological factors and agroforestry practices in Central Ethiopia

Deforestation and forest degradation in the tropics have led to significant carbon (C) emissions. Agroforestry (AF) practices are suitable land-use options for tackling such declines in ecosystem services, including climate change (CC) mitigation and biodiversity conservation. However, it is unclear how biomass models, AF practices, and socioecological factors determine these roles, which hinder the implementation of climate change mitigation initiatives. This study aimed to i) evaluate the biomass carbon and soil organic carbon (SOC) stocks of the three AF practices in relation to socioecological variables in central Ethiopia, and ii) compare the biomass carbon stock using different allometric models. Three AF practices were considered, namely, homegardens, parklands, and woodlots. A total of 432 soil samples were collected from 0–30 and 30–60 cm soil depths. Out of this total, 216 samples were used to determine the soil organic carbon fraction (%C), while the remaining 216 samples were used to calculate the bulk density. The study found that the currently developed allometric equations were the most accurate to estimate biomass carbon stocks in the landscape when compared to previous models. The study found a higher overall biomass C stock in woodlots (165.6 Mg ha⁻¹) than in homegardens (134.1 Mg ha⁻¹) and parklands (20.0 Mg ha⁻¹). Conversely, overall, SOC stock was higher for homegardens (143.9 Mg ha⁻¹), but lower for parklands (53.4 Mg ha⁻¹). The total C stock (biomass carbon and SOC stocks) was comparable between homegardens (277.9 Mg ha⁻¹) and woodlots (275.4 Mg ha⁻¹). The study found that elevation, wealth levels, AF farm age, and size have a positive and significant (P < 0.05) effect on overall biomass C stock but non-significant with slope (P > 0.05). Similarly, SOC stock increased with increasing elevation, AF farm age, and wealth status but decreased with slope and non-significant with AF farm size. The study also showed that species diversity had a positive (P < 0.05) effect on overall biomass C stock in homegardens. The overall study highlights that AF practices have great potential to lock up more carbon in biomass and soils; however, these potentials were determined by socioecological variables. Thus, these factors should be considered in management strategies that preserve trees in agricultural landscapes in order to mitigate climate change and support the livelihoods of farmers.