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A new colour vegetation map for Western Australia has been developed at a level of detail appropriate for publishing at the 1:3,000,000 scale. This memoir accompanies the map, which is based on the statewide mapping carried out by John Beard. The published maps and reports have been valuable resources for biologists and planners for decades, and this information is now available as a spatial dataset, making it more accessible for a broader range of uses. This memoir explains how the data were derived and describes the units of vegetation shown on the map. The 1:3,000,000-scale vegetation map shows the distribution of 75 major categories of natural plant cover in Western Australia as they would have been at the time of European settlement, with 50 major vegetation types, five categories of bare and poorly-vegetated ground and 20 vegetation mosaics (combinations of vegetation types). This classification was carried out in 1996-97 and is influenced by the original framework developed by Beard for the earlier 1:3,000,000 map. Vegetation types range from tall forests of karri (Eucalyptus diversicolor) in the high rainfall zone of the South West; through to the forests and woodlands dominated by eucalyptus, melaleuca, allocasuarina or acacia in the medium to low rainfall areas; the sclerophyllous shrublands of the South West; the saltbush, bluebush and samphire shrublands that occur on saline soils throughout the state; and the various grasslands of Triodia (spinifex) in central parts and Sorghum, Astrebla and Chrysopogon in northern parts of the state. These grasslands often have emergent tree cover of over 10% with density and are described as steppe or savanna. The map has been generated from a comprehensive, spatial database of the vegetation of the state, based mainly on the work of JS Beard carried out from 1964 to 1981. Almost 900 vegetation associations, derived from the 1:250,000- scale maps are included in the database. These were grouped into vegetation types based on physiognomy, floristics and, in some cases, ecological and regional attributes, and largely followed the framework developed by Beard. This work was carried out prior to the development of the National Vegetation Information System (NVIS; ESCAVI 2003). A subsequent reclassification of system associations (an intersection of Beard's vegetation associations with his vegetation systems) was described in six levels according to the NVIS, but is not described in this publication. The structure, composition, and general distribution of each of the vegetation types are described in this memoir . The memoir also includes details about the development and current delineation of the bioregions known as the IBRA (Interim Biogeographic Regionalisation of Australia). The description of vegetation types are referenced to these regions. The six most extensive vegetation types are: * low woodland, open low and sparse woodland dominated by Acacia aneura (mulga), which covers over 36 million ha and extends over eight IBRA regions; * a mosaic of open tree steppe and open shrub-steppe that covers over 25.5 million ha and dominates three desert IBRA regions; * shrub-steppe of hummock grassland dominated by Triodia spp. with scattered shrubs of Acacia spp. and Grevillea spp., mapped over nearly 25 million ha; * scrub, open scrub and sparse shrub of Acacia spp., Melaleuca spp. and other species, mapped widely over the state and that covers over 15 million ha; * the woodlands of the Avon Wheatbelt Bioregion, Coolgardie Bioregion, riverine areas and the Northern Kimberley Bioregion that cover nearly 13.5 million ha. These six vegetation types account for 55% of the state. The six most restricted vegetation types identified by the classification process are: * freshwater lakes, which total nearly 22,700 ha; * samphire with scattered trees or low trees, mapped over nearly 39,000 ha; * pockets of low forest of acacia, Rottnest cypress, coastal moort or mixed tropical forest (rain forest), which cover 55,600 ha; * sedgelands of the South West (59,000 ha); * thickets with medium open woodland or scattered trees (62,600 ha); * low woodland or open low woodlands over bluebush and/or saltbush (87,700 ha). Some of these could be incorporated into other units in future classifications. The 1:3,000,000-scale map gives a general impression of the vegetation of the state, as well as aspects of the geology, geomorphology and climate patterns. The vegetation database that underpins this map is currently being used for a wide range of research and planning purposes, including the on-going development of the terrestrial nature conservation reserve system. It is not ideal for this latter purpose as the scale of the mapping at 1:250,000 is relatively broad. More detailed vegetation datasets will be required to undertake more effective land use planning as conserving Western Australia's unique and fragile native vegetation communities becomes more challenging into the future. [ABSTRACT FROM AUTHOR] |
