Australian Native Vegetation Assessment 2001
Maria Cofinas, Colin Creighton
National Land and Water Resources Audit, 2001
ISBN 0 642 37128 8
Appendix 10: Methods to derive Major Vegetation Groups and Major Vegetation Subgroups
Mapping Australia's native vegetation at continental scales
The size and complexity of the National Vegetation Information System data sets presented a series of technical difficulties in accessing the data and interpreting it conceptually or spatially above regional scales. To provide a continental overview of native vegetation that would be discernible at broad mapping scales and that would be easy for a wide range of users to interpret was a major restriction on the level of detail that could be used.
Large scale maps of 1:40 000 000 scale which form the basis for the user interface in the Australian Natural Resources Atlas and this report necessitated the analysis be restricted to a small number of vegetation types.
The majority of the vegetation data compiled into the National Vegetation Information System has been mapped at between 1:250 000 to 1:100 000 scale. It includes some very broad-scale data, for example from the Northern Territory which was at 1:1 000 000 scale. The fine scales of mapping present a complex set of line work for representation at State and Territory and Australia-wide scales and many difficulties in ensuring continuity in map units across state borders and map sheets. Amalgamation of the spatial data for mapping units defined at association (Level V), or sometimes at subassociation (Level VI) level, into major groups for this overview of Australia's vegetation helped overcome some of these difficulties with the finer scale mapping.
Resolving classification inconsistencies
A manual assignment of the map units to the major vegetation groups was undertaken. As data collection further develops with resolution of inconsistencies in the nomenclature or description of some attributes and in the assignment of attributes at some levels, it will become possible to directly interrogate the data. This will result in minimising the risk of errors in the allocation of structural categories. Inconsistencies were addressed by checking the species present in Level IV and if need be in Level V or the State/Territory map unit descriptions.
Some vegetation community descriptors not related to structural attributes alone caused some problems (e.g. heaths proved to be problematic, with no clear definition of what communities should be included under this label). Care was taken in the development of the major vegetation groups to include not just the southern ericoid heaths but related tropical communities and other closed shrublands, particularly in South Australia. South Australia does not use heath as a descriptor in plant community definition. Advice was sought on what taxa were the best indicators of 'heath' communities in this situation.
Another major difference in nomenclature was related to jurisdictions describing similar communities at Level III as chenopod in one state and samphire in another.
Development of the major vegetation groups
Twenty-three major vegetation groups were delineated across Australia. Many of these vegetation groups are widespread and contain a large number of vegetation associations and sub-associations. Some groups such as rainforests are comparatively restricted and isolated in their occurrence.
The stratification and aggregation of the '100 plus' structural attributes (Level II) was the first step in the development of the major vegetation groups. The criteria for this stratification included:
- major structural groups recognised and commonly used in overviews and discussions on vegetation by the States/ Territories and other agencies. This was determined from a review of State/Territory vegetation overviews, recognising that one of the strengths of the National Vegetation Information System is that vegetation descriptions relate to dominant vegetation, not just upper stratum descriptors;
- groupings that help overcome some of the inconsistencies in nomenclature and description of vegetation units by the jurisdictions (e.g. putting samphire and chenopods in the same group); and
- distinct environments worthy of separate discussion in vegetation analyses (e.g. rainforest, mangrove/saltmarsh communities).
This process included a review of previous Australia-wide overviews of vegetation by Australian Surveying and Land Information Group (1990) and Beadle (1981), with cognisance of the limitations of being able discern the different classes either on-screen or on hardcopy maps.
Although the major vegetation groups were developed for national and State and Territory summaries of the vegetation data, they are valuable in providing context for more detailed vegetation descriptions at regional scales.
Development of more detailed major vegetation subgroups
A further stratification of the major vegetation groups was undertaken to more clearly define the extent of and type of major ecosystems or vegetation communities at scales near 1:5,000,000.
A stratification of the data was sought which, in combination, would allow appropriate aggregation for the display of vegetation data at a range of mapping scales. For maps produced at larger scales more detail is discernible and hence a larger number of mapping units than the 23 major vegetation groups is possible.
The data were stratified into a series of logical subgroups based on either:
- the genera used as the primary descriptor of the dominant stratum-major vegetation groups, Level III and Level IV (e.g. eucalypt woodland);
- their occurrence within broad geographical regions; and
- their species composition (e.g. rainforest taxa) or where the assignment of dominant genera in the dominant stratum has been difficult but the communities are typified by a distinct suite of taxa in the Level IV and Level V data (e.g. tropical mixed species forests and woodlands).
The geographic stratification undertaken reflects broadly the major climatic determinants influencing vegetation, its structure and distribution, namely:
- tropical includes the wet and dry tropics (minus the semi-arid lands);
- eastern Australia from coastal and inland areas east of the arid land zone from Townsville south to and including Tasmania, then west to Adelaide;
- arid and semi-arid zone; and
- south-west Australia the south-western corner of Western Australia.
One of the areas in vegetation mapping where there is a large divergence of approaches by the jurisdictions is the description of eucalypt forest and woodland communities. Several States/Territories talk about dry or wet forests but these descriptors, in isolation from the list of taxa present in each community do not convey a clear sense of what environments these forests represent. Victoria uses descriptors such as 'shrubby dry forest' that provides an immediate insight into these environments.
A proposed stratification of the occurrence of vegetation communities dominated by eucalypts was applied which greatly improves the interpretation and analysis of the data and provides a better insight into the physical environments covered by each mapping unit (Commonwealth of Australia 1997b). Mallee is a structural attribute so this category is already addressed in the data, and the arid zone catena of eucalypts is accounted for by a geographical stratification as are the monsoon forests and woodlands.
A similar stratification was undertaken for the acacia communities beyond a straight geographical split, particularly for mulga communities because of the broad range of environments in which they occur across a very large geographic area (e.g. the presence of spinifex or other notable taxa in the ground layer or shrub layer provide a cogent basis for such stratification and is readily determined from the data).
A proposed aggregation suitable for 1:5 000 000 map production, using such a schema, is presented in Table A1. The major vegetation subgroups will be available on the Australian Natural Resources Atlas.
| Rainforest and vine thickets |
|---|
| Cool temperate rainforest |
| Tropical and sub-tropical rainforest, dry rainforest and vine thickets |
| Eucalypt tall open forests |
| Eucalypt tall open forests and eucalypt forests with a dense broad leaved understorey (wet sclerophyll) |
| Eucalypt open forests and eucalypt low open forests |
| Eucalypt forests with a shrubby understorey |
| Eucalypt forests with a grassy understorey |
| Eucalypt forests with a heath understorey |
| Tropical eucalypt mixed species forests and woodlands |
| Tropical eucalypt woodlands/grasslands |
| Tropical eucalypt forests and woodlands with a annual grassy understorey |
| Eucalypt woodlands and eucalypt open woodlands |
| Eucalypt woodlands with a shrubby understorey |
| Eucalypt woodlands with a grassy understorey |
| Low tropical eucalypt forests and woodlands |
| Tropical eucalypt mixed species forests and woodlands |
| Callitris forests and woodlands |
| Callitris forests and woodlands |
| Acacia forests and woodlands |
| Brigalow (Acacia harpophylla) forests and woodlands |
| Other acacia forests and woodlands |
| Melaleuca forests and woodlands |
| Melaleuca forests and woodlands |
| Other forests and woodlands |
| Other forests and woodlands |
| Aggregation of several major vegetation group sub-components |
| Alpine and subalpine woodlands, shrublands, sedgelands and herbfields |
| Eucalypt open woodlands |
| Arid eucalypt low open woodlands with hummock grass |
| Arid eucalypt low open woodlands with tussock grass |
| Acacia forests and woodlands, acacia open woodlands and acacia shrublands |
| Mulga (Acacia aneura) woodlands and low open woodlands |
| Mixed species arid acacia woodlands and shrublands |
| Arid acacia low open woodlands and shrublands with chenopods |
| Arid acacia low open woodlands and shrublands with hummock grass |
| Arid acacia low open woodlands and shrublands with tussock grass |
| Other low open woodlands and shrublands with tussock grass |
| Casuarina forests and woodlands |
| Casuarina and Allocasuarina forests and woodlands |
| Mallee woodlands and shrublands |
| Mallee eucalypt low open woodlands |
| Mallee heath and shrublands |
| Low closed forests and closed shrublands |
| Low closed forests and tall closed shrublands |
| Heath |
| Heath plus banksia woodlands and shrublands |
| Chenopod shrubs, samphire shrubs and forblands |
| Chenopod shrublands |
| Other shrublands |
| Other shrublands |
| Hummock grasslands |
| Spinifex hummock grasslands |
| Tussock grasslands |
| Mitchell grass (Astrebla) tussock grasslands |
| Blue grass (Dichanthium) and tall bunch grass (Chrysopogon) tussock grasslands |
| Other tussock grasslands |
| Other grasslands, herblands, sedgelands and rushlands |
| Other grasslands |
| Herblands, sedgelands and rushlands |
| Chenopod shrubs, samphire shrubs and forblands |
| Mixed chenopods, samphires and forblands |
| Mangroves, tidal mudflats, samphires and bare areas, claypan, sand, rock, salt lakes, lagoons, freshwater lakes |
| Mangroves, tidal mudflats and coastal samphires |
| Bare areas, rock, sand, claypan, salt lakes and lagoons |
| Freshwater lakes |
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