Temporal variation in species composition, diversity and regeneration status along altitudinal gradient and slope: The case of Chilimo dry Afromontane forest in the Central Highlands of Ethiopia

This study is aimed towards investigating the temporal variation in species composition, diversity and regeneration status of Chilimo dry Afromontane forest in the Central Highlands of Ethiopia. A total of 35 permanent sample plots of 20 m × 20 m (400 m2) each were established in the natural forest, laid out on transects of altitudinal gradients, with a distance of 100m between plots. The plots were measured twice in 2012 and 2017. Three subplots, 5m × 5m, and 1 m2 were laid out inside the main plots for sapling, shrub and seedling data collection. Species composition, diversity, important value index (IVI) and regeneration data were analyzed using appropriate formulas. Data analysis was made using R - studio software. A total of 31 trees and shrubs representing 25 families were recorded, 20 (64.52 %) were trees and 11 (35.48 %) were shrubs. Thereof, 28, 23 and 26 species under highest, middle and lowest altitudinal gradient were recorded. The most dominant tree species were: Juniperus procera, Podocarpus falcatus, Olea europea, Scolopia theifolia and Allophyllus abyssinicus. The species composition, diversity, abundance, dominance and important value index significantly varied among species, altitudinal gradient and slope. The diameter distribution was an inverted J - shaped distribution pattern. The highest species richness and diversity index were found under middle altitudinal gradient, while the lowest species richness and diversity index were found under the highest altitudinal gradient. The mean annual volume increment ranged from 4.223 to 0.228 m3 ha-1 yr-1, while the basal area increment varied from 0.85 to 0.020 m2 ha-1 yr-1. Among the sampled species, ten species had fair, 5 poor and 14 species had no regeneration. In conclusion, the Chilimo dry Afromontane forest is suffering from low recruitment and regeneration. Thus, appropriate forest management options should be implemented.