Carbon stocks and sequestration potential of local avocado trees (Persea americana Mill.) in agroforestry systems of Tanzania

Abstract

Despite its widespread cultivation among smallholder farmers, our understanding of the capacity of the agroforestry tree species Persea americana (avocado) to absorb and sequester carbon has remained adamantly limited. Therefore, this study systematically evaluated the potential of avocado trees for above- and belowground carbon sequestration across six districts in Tanzania. Field surveys enumerated 270 mature individual trees, and the diameter at breast height (1.3 m above ground) of individual trees was measured to compute biomass and carbon stock variables. A species-specific allometric model for avocado was used to estimate both above- and belowground carbon stocks. Variations in carbon biomass variables were analysed using one-way analysis of variance (ANOVA) with the general linear model, considering district as the factor to assess significant differences among districts. The results showed significant variation in carbon stock variables (p < 0.05). Trees from Moshi District recorded the highest mean values: AGB (1.95 ± 0.16 Mg tree− 1), AGCS (0.93 ± 0.08 Mg C tree− 1), BGB (0.39 ± 0.03 Mg C tree− 1), BGCS (0.18 ± 0.01 Mg C tree− 1), TLB (2.34 ± 0.19 Mg tree− 1), TLBCS (1.09 ± 0.09 Mg C tree− 1), and CO2e (4.04 ± 0.34 Mg tree− 1). In contrast, trees from Karatu District recorded the lowest values: 0.62 ± 0.03, 0.29 ± 0.01, 0.12 ± 0.01, 0.06 ± 0.003, 0.75 ± 0.04, 0.35 ± 0.02, and 1.29 ± 0.65 Mg tree− 1, respectively. This study is the first in Tanzania to show that local avocado trees are a potential sink in agroforestry systems. This finding has important implications for climate change mitigation, improving economic returns, and increasing livelihood resilience for smallholder farmers. It also provides evidence to support the integration of perennial fruit trees into national agroforestry and carbon policy frameworks.