Rehabilitation options for degraded secondary forests in Adiyo district of Kaffa zone, Southwest Ethiopia

Abstract

Forest degradation is a very serious environmental problem. It leads to decline of biodiversity and ecosystem services. Thus, the objective of the study was to identify rehabilitation options for the degraded secondary forest in the Adiyo district in southwest Ethiopia. Data were collected from 30 quadrats (20 m × 20 m) across five treatments established for three years to examine stand structures, diversity, regeneration status of woody species, and enriched planting. The diameter at breast height (DBH) and height (H) of woody species were measured in the main quadrats and their seedlings and sapling were counted in the five subplots (4 m × 4 m) inside each main quadrat. A complete random design with three replications was employed to examine the growth performance and survival of planted trees with two permanent blocks having an area of 10,000m2. The diversity and evenness of woody species were estimated using Shannon Diversity Index (H') and Evenness (E). The importance value index (IVI) of woody plants was calculated to identify the status of ecologically significant species. A total of 30 woody species belonging to 27 genera and 20 families were recorded. The dominance value in the combination of assisted and enrichment of planting (CAREP) treatment reached 3.7 times higher than in open disturbed (OD) forest and exhibited a significant difference at p < 0.05. Shannon (H') and Simpson (D) diversity values also exhibited maximum in CAREP (H' = 2.60, D = 0.91) than other treatments. The highest IVI of woody species, the healthy population structure pattern, and potential regeneration species were found in CAREP treatment. Similarly, seedlings of H abyssinica, P. africana, and S. abyssinica demonstrated higher growth performance (3.41 to 4.35 m) and survival rate (76 to 85%) in the CAREP than in other treatments. In conclusion, the stand structure, diversity and regeneration status of woody species as well as the survival rate and growth performance of enriched species exhibited improvement in the CAREP treatment. It should be the best rehabilitation option for degraded secondary forest and need to be promoted for further adoption.