Shade tree diversity, structure, and regeneration dynamics in the Sheko semi-forest coffee agro ecosystem, southwest...

Shade trees in coffee agro ecosystem provide ecological and socio-economic benefits, including biodiversity conservation, microclimate regulation, and soil fertility maintenance. The Sheko semi-forest coffee system in southwestern Ethiopia is a traditional low-intensity landscape, yet its shade tree diversity, structure, and regeneration dynamics remain poorly documented.

Vegetation surveys were conducted across six purposively selected kebeles along an altitudinal gradient (950-1800 m a.s.l.) using 50 systematically placed plots (30 × 30 m). Each plot included five nested subplots (5 × 5 m) to assess seedlings and saplings. Shade trees were identified through field observations, local knowledge, and herbarium references. Structural attributes including density, basal area, diameter at breast height (DBH), height, and importance value index were measured. Data were analyzed using R 4.3.1 with descriptive statistics, ANOVA, correlation analyses, and Canonical Correspondence Analysis (CCA).

A total of 31 shade tree species across 15 families and 23 genera were recorded, with 96.7% native. Moraceae (32.2%) and Fabaceae (16.1%) were dominant. Cordia africana Lam., Pouteria adolfi-friederici (Engl.) Baehni, and Antiaris toxicaria lesch accounted for over 50% of density and basal area, with Cordia africana having the highest IVI (36.3). DBH and height distributions indicated a mixed-aged population, yet seedlings and saplings were underrepresented, reflecting limited regeneration. Altitude showed no significant effect on species richness or density. Anthropogenic disturbances, including clearing and unsustainable harvesting, constrained natural regeneration.

The Sheko semi-forest coffee system supports high shade tree diversity but faces regeneration bottlenecks that threaten long-term sustainability. Targeted management, including enrichment planting and protection of key species, is essential to maintain ecosystem services and agroforestry resilience.