Changes in plant diversity and carbon stocks along the successional gradients of Ethiopian Dry Afromontane forests

Debates persist regarding the extent to which successional forests can contribute to carbon (C) sequestration and biodiversity enhancement. This study aims to elucidate the relationships between plant diversity, biomass C, and soil organic carbon (SOC) across successional stages in the Dry Afromontane Forest (DAF) ecosystem of Jello-Muktar, Southeast Ethiopia. Employing a stratified sampling design, nine sites representing early (ES), intermediate (IS), and mature (MS) stages were surveyed, with 72 plots systematically established for comprehensive data collection. Vegetation was characterized through species richness (S), Shannon diversity (H), effective number of species (ENS), and evenness (J) indices, while biomass C stocks were estimated using allometric models, and soil samples analyzed for SOC content and bulk density. Environmental variables such as elevation, slope, and site age were incorporated to assess their influence on plant diversity and C stocks. Results indicate that a total of 113 woody plant species were recorded and there was a significant increase in S, H, ENS and J indices, and C stocks with forest succession. MS forests exhibited higher biomass C and SOC stocks, contributing approximately 48% of total ecosystem C, compared to 19% in ES. Statistical analyses revealed that successional age positively influences C accumulation, with elevation and slope modulating these effects. Notably, interactions between age, elevation, and slope significantly affected biomass C and SOC stocks, underscoring the complex interplay of environmental factors in forest C dynamics. These findings provide critical insights for forest management and restoration strategies aimed at maximizing biodiversity and C sequestration, supporting climate change mitigation efforts within Ethiopian dry montane ecosystems and similar agroecology.