Wetland flora and vegetation of the Western Australian wheatbelt

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – Eight hundred and thirteen quadrats were surveyed to sample wetland vegetation throughout the wheatbelt and adjacent south coast of Western Australia, an area of ca. 220 000 km2. Two hundred and fourteen wetlands were intensively sampled with between one and ten quad rats placed at each wetland to capture the major vegetation zonation. A further 100 quadrats were scattered through the study area to sample particular examples of wetland vegetation. Sampling spanned the full range of elevations at wetlands from inundated basins to the adjacent landforms such as lunettes.

A total of 1436 taxa of vascular plants from 109 families were recorded. Naturalized taxa were 11.8% of the flora. Four hundred and twenty-eight taxa (29.7%) were categorized as restricted to wetland habitats. These included both aquatic (53 taxa) and amphibious plants (89 taxa). The wetlands of the study area represent the world centre of diversity for annual Juncaginaceae and the subfamily Salicornioideae (Chenopodiaceae).

Species richness of quadrats (100 m2) ranged from 1-72 taxa, with a mean of 20.5 taxa per quadrat. Thirty-one per cent of taxa only occurred at a single quadrat (singletons) and 59.3% occurred at less than five quadrats. Eight previously unrecognized taxa were collected for the first time and the habitats and distributions of several undescribed taxa with few previous collections were clarified. Collections were made of 78 taxa listed on the Department of Conservation and Land Management's priority flora list. Eight of these were gazetted as Declared Rare Flora (Wildlife Conservation Act, 1950) with two (Frankenia conferta and F. parvula) regarded as extinct prior to the current survey.

Detailed cluster analysis was conducted on a reduced dataset (980 taxa by 760 quadrats) that excluded singleton species and some species-poor quad rats. A classification of 26 quadrat groups was defined. The primary division in the quadrat classification separated quadrats of inland largely naturally saline wetlands from quadrats at non-saline wetlands and at various wetland types with coastal and southwestern distributions. Lower levels in the classification were strongly related to local elevation and edaphic attributes of quadrats.

Thirty-four assemblages were defined from species cluster analysis and 29 were regarded as coherent species groups. The richness patterns of assemblages were modeled against 34 environmental attributes. Models explained between 26% and 74% of total deviance. Modeling was complicated by some assemblages having few members. Of the parameters used in the modeling, elevation at wetlands, substrate, electrical conductivity and pH were the dominant variables of models with the greatest decrease in deviance. Most assemblages were geographically well defined with annual precipitation and annual temperature range being important regional scalars. Fifteen plant assemblages containing 472 native taxa are identified as being at particular risk from secondary salinisation. They include assemblages of both non-saline and naturally saline wetlands.

Author(s) M.N. Lyons, N. Gibson, G.J. Keighery and S.D. Lyons
Volume
Supplement 67 : A Biodiversity survey of the Western Australian agricultural zone
Article Published
2004
Page Number
39

DOI
10.18195/issn.0313-122x.67.2004.039-089