Department of Plant Biology & Biodiversity Management, College of Natural and Computational Sciences, Addis Ababa University, National Herbarium, Addis Ababa, Ethiopia.
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.
PLoS One. 2018 Oct 17;13(10):e0204733. doi: 10.1371/journal.pone.0204733. eCollection 2018.
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.
本研究的主要目的是研究埃塞俄比亚西南部旺奇沃尔加河沿岸木本物种组成和多样性的状况。采用系统抽样法，沿河道每隔 500 米布置 50 个 10 m x 50 m 的样方。仅测量树木物种的植被高度（≥2.5 m）和胸径（≥2.5 cm），并在每个采样点纳入海拔、生态干扰（如放牧强度和人为干扰）等主要环境变量。数据使用不同的 R 统计软件包进行分析。在沃尔加河流沿岸植被中记录到 99 种木本维管植物，隶属于 81 属和 45 科。只有 10%的物种是该植物区系特有的。菊科和豆科的物种最多。大多数物种（52.5%）为灌木。确定了 4 种主要的植物群落类型：Euclea divinorum-Maytenus arbutifolia（1）、Pterolobium stellatum-Calpurnia aurea（2）、Brucea antidysenterica-Prunus africana（3）、Erica arborea-Hagenia abyssinica（4）。物种丰富度、真实多样性和重要值在海拔最低的群落类型 2（1976-2212 m a.s.l.）最高，均匀度在海拔中等的群落类型 3（2359-2676 m a.s.l.）最高。这两种群落类型都包含了记录物种的 56%和所有特有分类群，除了两个。较低频率类别的物种比例较高表明植物区系的异质性程度较高。物种丰富度与海拔呈强烈负相关（r = -0.65，p<0.001），海拔每升高 1 个单位，样方内物种丰富度的变化有 42%可以用海拔来解释。我们的研究结果表明，人类干扰和过度放牧是群落类型 1 和 2 面临的主要威胁。我们得出结论，确定主要的植物群落类型和潜在的环境条件可能有助于管理和保护该地区的森林资源。
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