Floristic diversity and biomass carbon stocks across elevation gradients in Ethiopian homegarden agroforestry

Abstract

This study investigates the floristic diversity and biomass carbon (BC) stocks in homegarden agroforestry (HGAF) across four Sites along varying elevation gradients at the eastern escarpment of Chercher Massif, Ethiopia. The objectives were to compare species diversity and BC stocks among sites, assess the effects of elevation and diversity on BC considering stand structure, plant origin, and life forms, and evaluate their interaction effects. A multistage sampling approach identified 120 HGAF farm households. Vegetation inventories within 20 m × 20 m plots measured perennial plants, Biomass estimated with allometric models was converted to carbon (C) stocks. Results revealed 115 plant species, with significant differences in species richness and diversity across Sites and elevation gradients. Trees constituted 51.3% of the species, with shrubs contributing 61.3% of the total number of stems. The mean total BC stock was 171.76 Mg C ha⁻¹ of which over 50% was contributed by trees, with significant variation across sites and along elevation gradients. Elevation and species diversity positively influenced BC stocks, with notable interaction effects indicating synergistic impacts. Native species significantly contributed to BC stocks than exotics, and life form significantly affected BC stocks distribution. Furthermore, the results of linear mixed models confirmed that elevation, and floristic diversity as key predictors of BC stocks, with significant interaction effects enhancing model explanatory power. The models explain a moderate proportion of variance in BC stocks, with marginal R² values of up to 54%. From a climate-smart agriculture perspective, this study highlights the importance of promoting floristic diversity and native species in HGAF to enhance BC stocks, thereby contributing to climate change mitigation. Regarding REDD + policies, the findings underscore the potential of elevational gradients and biodiversity conservation in AF landscapes to optimize C sequestration, supporting integrated strategies for forest and land management. These insights can inform policies that incentivize the conservation and sustainable management of AF systems, integrating biodiversity conservation with climate mitigation efforts under REDD + frameworks.