Influence of urbanisation on phytodiversity and some soil properties in riverine wetlands of Bamenda municipality, Cameroon

Abstract

In urban areas, human activities result in the discharge of a variety of chemical substances into the environment. This affects soil quality, plant species diversity and human security. To suggest appropriate management strategies that ensure soil quality and human security amid urbanization, this study assessed the relationship between macrophyte diversity and some soil characteristics of wetlands that are adjacent to urban, peri-urban and rural areas in Bamenda Municipality, Cameroon. Plant communities were sampled for species composition and relative abundance, using the Braun-banquet method. Species richness was evaluated using Simpson’s diversity index. Twenty-one soil samples (0–25 cm depth) were randomly collected within the wetlands and analyzed for their physicochemical characteristics using standard methods. The hierarchical cluster analysis (HCA) was used to group the wetlands under managing units. The dominant species ranked in order of abundance in the rural wetland were Raphia farinifera > Ludwigia hexandra > Coix spp. > Leersia hexandra > Ehchinochloa paramidelis. The Peri-urban wetland dominant species stood at Commelina bengalensis > Leersia hexandra > Cyperus distance > Ehchinochloa pyramidalis. In the Urban segment, Pennisetum purpureum > Echinochloa pyramidalis > Tithonia diversifolia > Leersia hexandra were the abundant species. The Simpson index of diversity was 0.94 for the urban and 0.96 for the peri-urban and rural sites respectively. The soils were slightly acidic with pH KCl ranging from 4.87 to 5.41. From the coefficient of variability classes, Sand, pH-H2O, pH-KCl, and Na consistently varied slightly across the three sites. Two significant clusters (management units) representing a combination of urban, and peri-urban/rural were formed from the hierarchical dendrograms. The Mann–Whitney U test revealed a significant (P < 0.05) lower exchange acidity in the rural than the urban sites indicating contamination of the urban site, reducing its macrophyte diversity. Intensification and extension of urbanisation are gradually reducing the macrophyte diversity and also contaminating the soils of the wetlands of the Bamenda municipality in Cameroon, warranting monitoring. The chemical composition of soils in the urban cluster needs early remediation by encouraging the planting and monitoring of certain plants that can already take up the elements.

Responses of Different Plant Taxonomic Groups to Complex Environmental Factors in Peri-Urban Wetlands

“…Van Wyk et al [13] demonstrated that stormwater discharges along urban streams can provide hydrologic conditions for vegetated habitats without other types of intervention or management. Asongwe et al [14] sampled urban wetlands and found that the expansion of urbanization has contaminated wetland soils in the city of Bamenda, resulting in progressively less wetland plant diversity. King and Hovick [6] investigated wetland plants along an urban to rural gradient and found that exotic plant richness and relative abundance were highest in urban sites.…”