A phytosociological study of Peat Swamp Forests in the Kosi Bay lake system, Maputaland, South Africa

Abstract

This study investigates patterns and processes in transformed and uncultivated Peat Swamp Forests (PSF) situated within the Kosi Bay Lake System Catchment (KBLSC) in north-eastern Maputaland, South Africa. Phytosociological investigations were performed to identify and describe the influence of recorded environmental factors and land use cultivation practices on PSF vegetation patterns (gradients and associations). PSF habitat were grouped into four mutually exclusive classes in the form of pristine, long-time recovering, recently disturbed and active gardening sites. Plant species were recorded separately in different forest strata, while peat profiles were sampled and described in selected Peat Swamp Forest valley bottom crosssections during fieldwork surveys in May and September of 2003. Multivariate analysis in the form of Agglomerative cluster analysis, Detrended correspondence analysis (DCA), Non-metric multidimensional scaling (NMDS) ordinations, and Indicator species analysis were used to identify and describe 5 Peat Swamp Forest communities associated with uncultivated and long-time recovering conditions (38 sampling plots), while 9 PSF communities were identified and described from the combined (four) PSF classes (65 sampling plots). Peat Swamp Forests were associated with channeled valley bottom and hillslope seepage inter– dune landscape settings that are connected to other watercourses within the Kosi Bay Lake System Catchment. The study found that Peat Swamp Forests are consistent with the definition of a phreatic (groundwater dependant) ecosystem, as they displayed indicators of prolonged groundwater-derived saturation, including peat development on slopes located above the active channel. Cultivation practices modified the structure and species composition of PSF, while their recovery after gardening abandonment appeared to be related to the wetness regime and the remaining peat body.