Do farm size, age, and wealth status influence plant species diversity in homegarden agroforestry systems in southeastern Ethiopia?

Homegarden agroforestry conserves biodiversity in the agricultural landscape. Farmers manage traditional and improved homegarden agroforestry system to enhance their food security and income. However, socioeconomic factors and agroforestry systems may influence the species composition and diversity of homegarden agroforestry systems, and there is limited study to make this assertion. The effects of homegarden practices, homegarden size, homegarden age, and household wealth status on plant diversity were investigated in southeast Ethiopia. Households’ homegardens were selected using a multistage sampling procedure. The Dello Mena and Harena Buluk districts in southeastern Ethiopia were chosen for the study due to the presence of both traditional and improved homegarden practices. Data were collected from 96 homegardens, constituting 200 nested sample plots, a plot size 20 × 20 m for an inventory of trees and shrubs. Additionally, five sub-plots (each 1 m × 1 m) were taken from each main sample plot to account tree seedlings and herbaceous plants. We identified 128 plant species across the studied homegardens, representing 103 genera and 52 families. Both traditional and improved homegarden agroforestry practices shared 76 plant species. Homegarden practices and homegarden size had a positive and significant effect on the plant species composition, Shannon diversity index, and Margalef species richness (p < 0.05). In contrast, homegarden age and household wealth status had no significant influence. The Shannon diversity index and Margalef species richness in the improved homegarden were by 25.2% and 21.6% higher, respectively, than in the traditional homegarden. We concluded that the efforts to conserve plant species diversity in homegarden agroforestry should consider the homegarden practices and homegarden size to enhance biodiversity conservation in the agricultural landscape of the study region and beyond. The study will also serve as a showcase to identify the manageable socioeconomic factors and agroforestry systems that can enhance the conservation of plant diversity to support local livelihoods and foster various ecosystem services.