Repercussion of traditional agroforestry practices on woody species diversity and carbon stocks in the Northwestern Highlands, Ethiopia

Agroforestry, as a platform for harmonizing agriculture and forestry is a win–win approach for the farming community and environmental sustainability. However, its potential is not well studied and quantified in Northwestern highland. Thus, this study aimed to investigate the woody species diversity, and carbon stock potential of traditional agroforestry practices in Northwestern Highlands (NWH) of Ethiopia. A total of 120 households were selected using stratified sampling for household (HH) surveys, and vegetation inventory was conducted in the winter season of 2023 on systematically laid 400 m² sample quadrats. Shannon-Weiner diversity index (H'), Simpson's diversity index (1-D) and Shannon evenness (E) were calculated to estimate woody species diversity. Variation in species diversity and carbon stock within and between agroforestry practices was assessed by 1-way ANOVA and rank differences were separated by post-hoc, Tukey HSD multiple comparison test. The result showed that four different agroforestry practices were identified, consisting of 44 woody species belonging to 23 families. Homegarden was the richest in terms of woody species composition (30), followed by boundary planting (25), while parkland agroforestry had the poorest species composition (12). The total carbon stock of the agroforestry practices in the study ranged from 92.51±29.21 to 143.52 ± 47.83 Mg/ha), with soil organic carbon accounting for about 57.66%, followed by aboveground biomass carbon with 32.1%. Homegardens agroforestry had contributed more to the total carbon stocks than the other agroforestry practices. The total CO₂ sequestration by above and below ground biomass of woody species in the traditional agroforestry practices of the NWH was estimated to be 519.97 and 104.01 Mg/ha, respectively. The study confirmed that the traditional agroforestry practices of the NWH of Ethiopia maintain a high diversity of woody species and are remarkably important for biodiversity conservation and climate change mitigation.