The ecology and plant functional composition of the afromontane palustrine wetlands in Lesotho

Abstract

The classification and description of wetland vegetation is important for biodiversity conservation and water resource management as it provides an understanding of the wetland vegetation-environment relationships and information to interpret spatial variation in plant communities. This study characterises the Afromontane palustrine wetlands of Lesotho in terms of plant communities, plant functional types and plant functional composition. Relationships of plant communities and functional traits were also explored. Vegetation, environmental and plant functional trait data were collected using the Braun-Blanquet method and standard methods. The data were analysed mainly by means of clustering, ordination and diversity analysis techniques. Twenty-two communities were produced by the classification of the Afromontane wetland vegetation and seven plant functional types, as well as seven functional communities were obtained from the classification. The wetland plant communities are diverse in terms of species richness. The ordination revealed that the wetland vegetation is mainly influenced by altitude, longitude, slope, soil parent material, landscape, inundation, peat, potassium content, soil texture, total organic carbon, nitrogen, sulphur, electrical conductivity, calcium, soil depth, wetness, magnesium, aspect and latitude. Plant functional traits and functional composition of the communities were found to be broadly influenced by altitude, slope, longitude, soil parent material, landscape and inundation, and more finely by edaphic factors that include electrical conductivity, calcium, sodium, magnesium, nitrogen, organic matter, total organic carbon, clay percentage, pH, sand percentage and potassium. Regarding species composition and diversity, plant communities in the Highlands were more diverse and were distinctively different from those in the Lowlands. Although a few wetlands, particularly in the Highlands are still in their near-pristine condition, many wetlands in the country are showing severe signs of degradation. While some communities are either restricted to the Highlands or Lowlands, others exhibit a wide ecological amplitude and occur in both regions. The study further highlights the possibility of alterations in plant functional traits, types and functional composition in the face of environmental changes, including climate change. The diversity of most of the wetlands, coupled with their restricted habitat and distribution at high altitudes and their role in supplying ecosystem services that include water resources, highlights the high conservation value associated with these wetlands, particularly in the face of climate change and loss of biodiversity.