Woody species diversity of traditional agroforestry practices in Gununo watershed in Wolayitta zone, Ethiopia.

Abstract

In Gununo watershed at Wolayitta zone, Ethiopia, to determine the variation of woody species structure and composition among agroforestry practices and along elevation gradients in the watershed, this study was conducted. The elevation gradient was stratified in to three transects (upper, middle and lower); and three dominant agroforestry practices (homegarden, parkland and woodlot) were used as treatments. Along each transect line, three agroforestry practices with three replications, a total of 27 sampling points, a complete enumeration of woody species in homegarden which has the average are of 900 m2. Whereas, 50 m × 100 m sampling quadrates in parklands, and 10 m × 10 m sample quadrates for woodlot were used. Number of individuals per plot, DBH, height, crown diameter, and plot area were measured and recorded. The structure and composition of woody species through important value index (IVI), basal area, canopy cover, and diversity indexes determine were determined. A total of 32 woody species belonging to 19 families were recorded in the three agroforestry practices. Fabaceae family 28%, (9 species) was the dominant family of the woody species recorded followed by Euphorbiaceae 13%, (4 species). From these species, 69% (22 species) were indigenous and 31% (10 species) were exotic. From the indigenous species, two were endemic to Ethiopia (Erythrina brucei and Millettia ferruginea). The largest indigenous species, and highest species diversity (20) were recorded in homegardens followed by parklands (11)). Middle elevation was exhibited higher indigenous species, and highest species richness (19): followed by upper (15) and lower elevation. The Shannon, Simpson and evenness diversity indexes were highest in homegardens. Comparing to parkland, homegarden diversity indexes were highest in upper, middle and lower elevations in decreasing order. Attention should be given to the existing agroforestry practices, and the practices must be promoted to lower elevation to enhance biodiversity conservation in agroforestry land use system.