Australian Vegetation Attribute Manual

National Vegetation Information System, Version 6.0
Executive Steering Committee for Australian Vegetation Information (ESCAVI)
Department of the Environment and Heritage, 2003
ISBN 0 642 54953 2

Section Two: The NVIS Framework - Concepts and Standard Procedures

The NVIS Framework provides a comprehensive means of describing and representing vegetation types, based on establishing relationships between structural and floristic information in a Relational Database Management System. Figure 2 shows two example vegetation profile diagrams showing sub-strata. One (or more) site descriptions may be interpreted to become a unique vegetation description at NVIS Level VI. Figure 3 shows a summary of cover classes in each stratum.
Figure 2
Figure 2: Vegetation profiles for two different vegetation types, showing the flexibility in assignment of sub-strata (U1, U2, etc.- see Table 2). These become key inputs for NVIS Descriptions at Level VI. For interpreting the vegetation at NVIS Level V, only the strata U, M and G are recognised.
Figure 3
Figure 3: Graphical summary of cover values for an example NVIS Description at Level V. Stratum U (height class 7) has a cover code mid-point of 35%; stratum M (height class 4) has a cover code mid point of 0.125% and Stratum G (height class 1) has a cover code mid-point of 65%. (The NVIS Level V description of this community is: U+ ^Eucalyptus populnea/^tree/7/i;M ^Eremophila mitchellii,Geijera parviflora/^shrub/4/bi;G ^Aristida ramosa,Dichanthium sericeum,Themeda triandra/^tussock grass,forb/1/c).

Provided all attributes are consistently compiled at a "complex" level, summary data products can be derived using rule sets plus expert input. Current progress with the development of rule sets is documented in Section 4 of this Manual.

The following sub-sections describe the attributes and their relationships and how they are managed within the NVIS Framework. Details of each attribute are presented in Section 3. Appendix A is a glossary of key terms and definitions, which underpin the NVIS Framework.

One approach to summarising vegetation descriptions is to create a hierarchy of information. The following text describes the NVIS Information Hierarchy. Additional levels and/or hierarchies can be incorporated to meet specialist needs, such as forestry, by modifying the attributes included at each level and by modifying the rule sets used to generate successively coarser levels.

The NVIS Information Hierarchy

The NVIS Information Hierarchy is based on six levels as shown in Table 1. The purposes of the Information Hierarchy are:

  • To define and therefore standardise the structural and floristic information needed within the different levels of the Information Hierarchy;
  • To provide a framework for quality control and assurance of vegetation description information; and
  • To provide a framework for generating outputs (eg. map products) at the various levels.
Table 1: The NVIS Information Hierarchy. The Levels below the dark line are the "complex" levels recommended for data compilation.
Hierarchical Level
Description
NVIS structural/floristic components required
I
Class*
Dominant growth form for the ecologically or structurally dominant stratum
II
Structural Formation*
Dominant growth form, cover and height for the ecologically or structurally dominant stratum.
III
Broad Floristic Formation**
Dominant growth form, cover, height and dominant land cover genus for the upper most or the ecologically or structurally dominant stratum.
IV
Sub-Formation**
Dominant growth form, cover, height and dominant genus for each of the three traditional strata. (i.e. Upper, Mid and Ground)
V
Association**
Dominant growth form, height, cover and species (3 species) for the three traditional strata. (i.e. Upper, Mid and Ground)
VI
Sub-Association**
Dominant growth form, height, cover and species (5 species) for all layers/sub-strata.
* Walker & Hopkins 1990
** NVIS (defined for the NVIS Information Hierarchy)

The threshold for input of vegetation description data into NVIS is Level V (the Association). At this level, the 3 traditional strata (Walker & Hopkins, 1990), as represented in Figures 2 and 3, are recognised where appropriate. (Not all plant communities have 3 strata.) For each stratum, the characteristic height and cover are recorded; also, up to 3 growth forms and up to 3 species can be used to describe the vegetation type at Level V.

The preferred level for input is Level VI (the Sub-Association). At this level, up to 8 sub-strata or layers are recognised (Table 2), with characteristic height and cover recorded for each sub-stratum; also, up to 5 growth forms and up to 5 species can be used to describe the vegetation type at Level VI.

While the NVIS Information Hierarchy can be used to translate and compile datasets that were collected at coarser levels than level V, this approach is not recommended. This is because the accurate and reliable use of rule sets that underpin the NVIS Information Hierarchy, require mandatory and essential attribute data (see Table 7) at Level V or VI, before these data can be aggregated to a higher level. Datasets not meeting the NVIS threshold will thus be of limited usefulness in the development of products. A detailed example of the information contained at each level of the NVIS hierarchy is given in Table 6.

The NVIS Information Hierarchy is based firstly on structural information and secondly on dominant genus and growth form collected at the sub-stratum level describing Level VI (Sub-Association level). This is illustrated in the examples shown for Levels V and VI (Association and Sub-Association) in Table 6.

Some benefits of the NVIS Information Hierarchy are as follows.

  • The input of vegetation description data at the "complex" levels (Levels V or VI) enables the automatic generation of simpler levels, thus maintaining consistency in the database as well as reducing workloads;
  • The Level V (Association) retains sufficient data to allow useful comparison with the Level VI (Sub-Association). This will be important where a jurisdiction can only enter data at level V.
  • Growth form information is retained in the middle levels of the hierarchy. One of the reasons for including growth form data is that it is often easier to recognise in the field.
  • Standardised descriptions provide the basis for comparing vegetation types between datasets with disparate mapping methods and hence identifying equivalent vegetation types.