The riparian flora and plant communities of the Pilbara region of Western Australia

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – A survey of riparian flora and plant communities was undertaken at 98 wetlands and rivers in the Pilbara region of Western Australia. Sampling was quadrat-based, with fl oristics, surface soils and wetland attributes recorded. Selected sites captured the full range of Pilbara wetland types including springs, river pools, claypans, salt marshes and rock pools. A total of 455 taxa was recorded from the survey sites, representing ca. 25% of the known fl ora of the Pilbara bioregion. The fl ora is dominated by taxa with Eremaean and tropical affi nities, with only six taxa endemic in the region. Of recorded taxa known from four or fewer bioregions, most are shared with the adjacent Carnarvon and Gascoyne bioregions rather than the adjoining internally draining deserts. Sixteen taxa of conservation signifi cance were documented, with claypans, the Fortescue Marsh, and Millstream and Karijini National Park sites dominating occurrences of rare species. Eight major groups were defined by classifying wetlands in terms of species presence/absence data. Floristic patterning was strongly aligned with the major wetland types (geomorphic/hydrological) used in the primary sampling stratifi cation. A combination of wetland morphology/hydrological setting, site edaphic attributes and distance to the coast were dominant variables related to riparian floristic composition. Primary compositional separation was observed between riverine and non-riverine sites, with lowland turbid riverine sites with finetextured soils compositionally related to claypans and clay flats. Limited biogeographic patterning was evident except where individual IBRA subregions and drainage basins were dominated by few wetland types.