Traditional agroforestry homegardens have been described as man-managed ecosystems with complex structure and multiple functions. Despite being an integral part of farming system in South West Ethiopia, this system is still poorly studied and understood. The study was conducted to assess the diversity and horizontal structure of woody species in homegardens at Gimbo district, South West Ethiopia. Two sites and two villages from each site were purposively selected. The data on species diversity in homegardens were collected from 120 plots. All trees and shrubs with diameter at breast height (DBH) ≥ 5 cm were counted and recorded in 10 m X 10 m plots, while vegetation data on saplings and seedlings were collected from 2 m x 2 m subplots. The number of woody species in the homegardens was 57, of which, 76% were indigenous while the remaining were exotic. Site and village level comparison showed some variation in terms of species richness. Keja Araba site supported higher number of woody species than Tula site. Diversity of woody species in the homegardens was variable. Lower diversity indices were recorded at the villages that were relatively the closest to the market. Woody species with high commercial value like Persea americana and Cordia africana were observed in the homegardens more frequently and abundantly at study villages, especially at villages more accessible to market. Sesbania sesban was the most frequent and abundant woody species in the homegardens at Shuba village. It was also one of the most abundant woody species at Tena village. Diameter distribution of the most important woody species in the homegardens showed higher abundance in the smaller diameter class and a decreasing trend to larger diameter classes. The high woody species diversity and presence of many rare/endangered species in the homegardens reflect the ways how small holder farmers manage, utilize and conserve plant diversity and hence play remarkably high role in conserving biodiversity.

Keywords: Biodiversity, horizontal structure, market, frequency, abundance, endangered, South West Ethiopia.