Exclosure-based woody species diversity and factors affecting its sustainability in the Shapha sub-watershed, Southern Ethiopia

Abstract

In the Shapha sub-watershed, an exclosure was implemented to restore the land and promote vegetation diversity. However, further scientific evidences are necessary to assess the impact of this intervention on woody species diversity and inform sustainable practices. Therefore, this study was designed to i) examine the diversity of woody species, population structure, and regeneration status compared with open grazing land and ii) assess factors affecting exclosure sustainability. The woody species inventory was made in 60 nested quadrants (20 m × 20 m) with eight parallel lines. Systematically, 90 respondents were asked and a focus group discussion was held. Data were analyzed using diversity indices, descriptive statistics, and a logistic regression model. The results reveal that 34 woody species were recorded across the two land-use types. As a result, 32 woody species belonging to 22 families and 29 genera within the exclosure and 11 types of woody plants from eight different families, comprising 10 other genera, were observed in the adjacent grazing area. It is hereby reported that the Shannon diversity indices for exclosure and adjacent open grazing lands were found to be 2.27 and 1.02, respectively. Similarly, the Simpson indices were 0.85 and 0.57, the evenness indices were 0.87 and 0.85, and the species richness values were 0.43 and 3.4, respectively. In the exclosure, woody species displayed a reverse J-shaped pattern in contrast to the J-shaped arrangement observed on the adjacent grazing land. Seven of the nine explanatory variables were crucial for determining the sustainability of the exclosure, with the exception of land tenure and family size. Notably, exclosure has proven to be the most effective for restoring degraded vegetation in the study area because they encourage the growth of new vegetation through natural regeneration.

Keywords

• Exclosure
• grazing land
• population structure
• sustainability
• woody species
• Agriculture & Environmental Sciences