The influence of human use patterns in shaping the ecological importance of perennial plant species in the Gedeo agroforestry systems, Southern Ethiopia

Abstract

Traditional agroforestry systems, particularly within Gedeo Landscape of Southern Ethiopia, play a vital role in maintaining both the well-being of local communities and the integrity of the ecosystem. However, little attention has been given to how the ecological significance perennial plant species aligns with their traditional uses, as suggested by the Ecological Apparency Hypothesis (EAH). To bridge this gap, our study explored the ecological roles and varied ethnobotanical applications of perennial plants across agroforestry systems distributed along varied elevation gradients in the study area. Multi-stage sampling method was employed to conduct vegetation surveys in 286 randomly selected households using 10 m × 10 m quadrats (total area of 2.86 hectares) and collecting ethnobotanical information through household surveys with 286 participants and 30 key informant. In doing so, we identified 78 perennial plant species spanning 34 families. Our Importance Value Index (IVI) analysis revealed Ensete ventricosum as the most dominant species (IVI = 92.041), with Coffee arabica and Millettia ferruginea (IVI = 33.626), and Cordia africana (IVI = 15.894) also highly significant. Ensete ventricosum and Millettia ferruginea were prevalent in Enset-tree systems, while these, alongside Coffee arabica, were common in Coffee-Enset-tree and Coffee-fruit-tree systems. Strong positive correlation (p < 0.001) was found between a species' overall Use Value and its IVI. This suggests that ecologically prominent species are highly valued and utilized by the community, supporting the EAH. This correlation was strong for uses such as construction (ρ = 0.190, p < 0.01), income generation (ρ = 0.228, p < 0.001), shade (ρ = 0.185, p < 0.01), soil fertility improvement (ρ = 0.299, p < 0.001), and energy (ρ = 0.232, p < 0.001). However, the EAH did not hold true for medicinal, food, and fodder species. High IVI species were specifically linked to certain uses: Millettia ferruginea and Cordia africana for shade, Ensete ventricosum and Cordia africana for income, and Cordia africana and Erythrina brucei for construction. While traditional knowledge on shade, energy, and fodder varied across agroforestry systems, it remained consistent for other uses. We also noted significant differences (p < 0.05) in how shade, fodder, and energy resources were utilized across different systems. These findings underscore the complex relationship between a species' ecological prominence and its diverse uses in Gedeo agroforestry. Understanding these dynamics is vital for developing sustainable development policies and conservation strategies that recognize the multifaceted value of these species, ultimately supporting ecosystem balance.