Woody species composition and diversity of riparian vegetation along the Walga River, Southwestern Ethiopia

Abstract

The primary objective of this study was to examine the status of woody species composition and diversity along the Walga River of Wonchi, Southwestern Ethiopia. Fifty quadrats of 10 m x 50 m were laid at 500 m interval through systematic sampling method along the river line. Vegetation height (≥2.5 m) and DBH (≥2.5 cm) of only tree species were measured and altitude, ecological disturbances such as, grazing intensity and human impacts were included as main environmental variables at each of the sampled plots. The data was analyzed using different R statistical packages. Ninety-nine woody vascular plant species belonged to 81 genera and 45 familieswere recorded in Walga riparian vegetation. Only 10% of specieswere endemic to the Flora area. Asteraceae and Fabaceae had the highest number of species. Majority of the species (52.5%) were shrubs. Four major plant community types were identified: Euclea divinorum-Maytenus arbutifolia (1), Pterolobium stellatum- Calpurnia aurea (2), Brucea antidysenterica-Prunus africana (3), Erica arborea-Hagenia abyssinica (4). Species richness, true diversity and importance values were highestin community type 2(the lowest altitude ranges between 1976–2212 m a.s.l.) while evenness was highestin community type 3(mid altitude ranges between 2359–2676 m a.s.l.). Both community typeswere comprised of 56% of all recorded species and all endemic taxa except two. The highest percentage of species in lower frequency classes indicates a higher degree of floristic heterogeneity. There was a strong negative correlation (r = -0.65, p<0.001) between species richness and altitude with 42% of the variation in species richness per plot being explained by altitude. Our findings suggest that human disturbances and excessive livestock grazing are the main threats in community types1 and 2. We conclude that identifying major plant community types and underlying environmental conditions may help to manage and conserve forest resources in the area.

Woody plant diversity, composition and structure in relation to environmental variables and land‐cover types in Lake Wanchi watershed, central highlands of Ethiopia

“…Woody species richness showed a monotonic decline with increasing elevation at Lake Wanchi watershed (Figure 4c). A similar effect was reported by Berhanu, Woldu, and Demissew (2017) and Meragiaw et al (2018) on elevation patterns of woody plant richness in the evergreen Afromontane vegetation of Ethiopia and woody species composition and diversity of riparian vegetation along the Walga River, Ethiopia, respectively. Our finding agrees with a study by Ohsawa (1995) that showed decreased species richness with an increase in elevation in a humid Asian mountain system.…”

“…This may be associated with the greater amount of solar radiation received on the east-facing slopes (Yirdaw et al, 2015). At Lake Wanchi watershed, east-facing slopes receive morning light, whereas afternoons are often cloudy, and this might reduce the solar radiation received by the west-facing slopes (see also Meragiaw, Woldu, Martinsen, & Singh, 2018).…”

Regeneration Status and Importance of Hyphaene thebaica L. (Doum Palm) and Associated Species in Tekeze Riverine Vegetation of the North Western Zone of Tigray, Northern Ethiopia

“…In other words, 11 tree species, 5 shrub species and 1 grass species were encountered in association with the study species, Hyphaene thebaica (Table 1). Species composition found in this study is very low compared to a study conducted by Belachew [11] in Beschillo and Abay (Blue Nile) riverine vegetation, Ethiopia (205 species and 53 families) and Meragiaw et al [14] in riparian vegetation along the Walga River, Southwestern Ethiopia (99 plant species belonging to 45 families). This may be due to envronmental limitations su-ch as low and erratic rainfall and human intervention in the area.…”

Quantification and characterization of vegetation and functional trait diversity of the riparian zones in protected forest of Kashmir Himalaya, India

“…Plants growing adjacent to and near a water body together form the riparian vegetation, which is one of the fifteen terrestrial biomes of the earth (Meragiaw et al 2018). Riparian zones are broadly defined as terrestrial (dry) landscapes with visible vegetation that interacts with temporary or permanent aquatic (wet) ecosystems (Meragiaw et al 2018). Riparian zones as ecotone are remarkably rich in biodiversity (Gregory et al 1991, Malanson 1993, Naiman et al 1993.…”