Impact of exclosures on woody species diversity in degraded lands: the case of Lemo in Southwestern Ethiopia

Woody species diversity and regeneration status of Sub-Alpine forest of Mount Adama exclosure site, Northwestern highlands of Ethiopia

Forests provide a wide range of ecosystem services. Despite these facts, the expansion of agriculture and settlement at the expense of forest resources has threatened the forest resources and results in biodiversity loss. To halt this problem, various conservation practices that believed to restore the degraded lands and biodiversity of the country have been implemented. Area exclosure is among the conservation strategies that have been used to restore the degraded lands in Mount Adama forest. However, its role in woody species regeneration in Mount Adama was not investigated. Thus, the objective of the study was to evaluate the impact of area exclosure on woody plant species composition, regeneration status, structure and diversity in Mount Adama. A systematic transect sampling method was used to collect vegetation data. Hence, 53 plots with 400 m² area were laid along 11 transects. Then, within the main plots, five subplots with 1 m² were laid to determine the abundance and frequency of seedlings. The results showed that about 31 woody species that belong to 30 genera and 19 families including four endemic species were identified. The majority (67.74%) of the species were categorized under shrub habitat, while the remaining 19.35% and 12.90% were trees and lianas or climbers, respectively. Asteraceae family was dominant by contributing 4 species followed by Rosaceae and Solanaceae each contributed 3 species. Hypericum revolutum was the dominant species with 53.38 important value index followed by Erica arborea and Hagenia abyssinica with 49.12 and 40.05, respectively. The overall Shannon- Wiener diversity index and Shannon evenness in the exclosure site were 2.6 and 0.73, respectively. Furthermore, the number of seedlings and saplings were higher in the exclosure than the untreated site. The results of the study evidently showed that area exclosure that implemented in Mount Adam successfully contributed to the biodiversity restoration. Therefore, further conservation efforts targeting species with low IVI values are needed for sustainable management and ecological recovery of the area.

Does exclosure restore woody species regeneration in degraded lands? The case of Loma Bosa District of Dawuro zone, Southwestern Ethiopia

Exclosure becomes popular as a naming of the practice of excluding degrading agents from degraded lands for natural rehabilitation. However, its role on woody species regeneration in the Loma Bosa District of the southwestern Ethiopia has not been investigated. Therefore, this study examines the role of exclosure on woody species regeneration by comparing exclosure, open woodland, and degraded land areas. A systematic transect sampling method was employed to collect vegetation data in sampling quadrats, each with a size of 20 × 20 m, evenly distributed along parallel transect lines. All the woody plant species in each plot were identified and measured for DBH and height. Twenty-six woody species, representing 16 plant families, were recorded at the study area, of which only eight were recorded all in the exclosure, open woodland and open degraded land. Species Diversity Index (H′) was 2.62, 2.38, and 1.56 for woody species in exclosure, open woodland area, and open degraded land area. Wood species density were 2225 ha−1, 1642 ha−1, and 297 ha−1 for exclosure, open woodland area, and open degraded land area, respectively. The distribution of the height and DBH of the recorded species in exclosure exhibited an inverted “J” shape pattern suggesting a healthy regeneration status of the important species, while others revealed irregular and less interpretable pattern. Overall results from this study indicated that exclosure is important for improvement of woody species regeneration in degraded lands in the study area.