Impact of altitude and anthropogenic disturbance on plant species composition, diversity, and structure at the Wof-Washa highlands of Ethiopia

Abstract

The study was conducted in Wof-Washa Forest in the central highlands of Ethiopia, aiming at determining the impact of altitude and anthropogenic disturbance on plant species composition, structure, and diversity of the forest. Eighteen transect lines with 632 meters apart from each other were established from top to bottom. A total of 115 main plots for all communities with 20 × 20 m, were established along transect lines from the upper part of the forest to the river's edge. To collect data on seedlings and saplings, 5 m × 5 m and 10 m × 10 m subplots were laid respectively within the main sampling plots. For each plot the plant species were counted, diameter at breast height and height of trees and shrubs were measured. The human disturbance data were visually estimated for each plot in each community. Plant community classification was made following Ethiopia agro-ecological zones. Plant species diversity and richness were found related to human disturbance and altitude. A total of 108 species belonging to 99 genera and 57 families were identified. The results revealed that Asteraceae was the most diverse higher plant family with nine species (8.3%) followed by Fabaceae, Euphorbiaceae, and Rosaceae with six (5.5%) species each. The overall Shannon diversity and evenness index of the forest were 4.02 and 0.86 respectively. Tree/shrub, sapling and seedling densities were 664.4, 757.2 and 805.7 individual's ha −1 respectively. The total basal area of the forest was 55.99 m 2 ha -1 . About 25.7% of the importance values index was contributed by four species, Juniperus procera, Podocarpus falcatus, Ilex mitis, and Erica arborea . The similarity in species composition within the forest was low, indicating that the different parts of the forest had different floras. The presence of strong human disturbance indicates the need for immediate conservation in order to ensure sustainable utilization and management of the forest.

Floristic Composition and Structure in Relation to Elevation in the Togo Plateau Forest Reserve in Ghana

“…The average Shannon-Weiner Index (H') (which is more sensitive to species richness) and evenness index for trees (3.99, 0.92) recorded in the study were higher than studies from similar ecosystems in Ghana including the Kade forest (2.37, 0.86; [20]), Afadzato Community Forest Conservation Area (2.24, 0.85; [21]) and Atiwa forest (2.65,0.84; [20]) and elsewhere (3.2, 0.58; [15]). The recorded values in this study were, however, lower than other similar studies including (4.05, 0.98; [23]) and (4.02, 0.96; [18]). Saplings and seedlings also follow a similar pattern in composition and structure.…”

“…4 and 6), which was in accordance with the findings from several plateau forests [15], [17], [23] an indication that the plateau is harbouring a growing and healthy vegetation, and the site resources are being utilized to the maximum [17], [23]. The DBH, however, revealed a similar vegetation distribution across the study communities [16], [18].…”

“…These dominance of these species in the Togo Plateau landscape might be associated with their regeneration success, pathogen resistance, shade tolerance, and aggressive growth, optimal resource use and dispersal mechanism, while being the least preferred by browsing animals and disturbance stress [28]. Interestingly, all the communities had wide distribution of these species and may reflect their tolerance of wide ecological conditions [18].…”

“…3, Table 5). The highest similarity was seen between BO and NK, suggesting that the two communities have similar vegetation requirements [18]. The distinct composition of AL from the rest of the communities may be due to its different altitude and associated environmental conditions which affect species growth and survival [18].…”

Floristic composition and vegetation community analysis of Gesha and Sayilem Forest in Kaffa Zone south western Ethiopia

“…However today, the forest cover in Ethiopia is estimated at about 2.5% (Badge 2001). The main causes for the shrinkage of the forest resource in Ethiopia are anthropogenic pressures like clearing and burning of natural forest for crop cultivation, settlements, and gathering of fuelwood and construction material (Sisay 2008;Tura et al 2017;Yirga et al 2019). These consequences reduce ecosystem services like carbon stocks, soil properties, and the hydrological cycle (Lal 2012).…”