Guidelines and Field Methodology for Vegetation Survey and Mapping

SECTION A: GUIDELINES
5.0 NVIS CLASSIFICATION FRAMEWORK AND
NOMENCLATURE
Classification plays an important role in vegetation survey and mapping. The primary goal of a
classification system is to define patterns and simplify complex vegetation data.
Traditionally, NRETA Land and Vegetation have used a modified Carnahan/Specht (1981)
classification system for pure vegetation mapping where vegetation is characterised by the tallest
stratum. The tallest stratum is also considered to be the dominant stratum, provided canopy cover
values are greater than 5%. For land unit mapping in the NT the Walker and Hopkins (1990)
classification system also characterises vegetation by the tallest stratum. The two classification
systems rely on slightly different criteria and once applied to a map are not directly comparable.
Similarly at the national level, State and Territory agencies involved in vegetation survey and
mapping have used different classification systems. Recognising this, a national standard, the
NVIS framework, for classifying vegetation map units and descriptions was developed.
The principle objective of vegetation survey is to identify vegetation communities with similar
characteristics (i.e. floristic, structural formation & environmental attributes) by:
1. Describing vegetation communities at a recognised classification level (i.e. NVIS
Information Hierarchy Level V – Association & Level VI - Sub-association; refer to
Chapter 5.1) for survey reports;
2. Attributing preliminary unique mapping areas at a recognised classification level
(generally Level V – Association; refer to Chapter 5.1) to establish regional patterns of
vegetation community distribution, and
3. Providing an understanding of ecosystem relationships by identifying links between
individual species distribution and co-occurrence with a set of environmental factors
(i.e. physical, biological & disturbance attributes).
To achieve the above, field data is analysed and classified into floristic and structural groupings
using a recognised classification system.
5.1 NVIS Structural Classification
The NVIS framework is based on an information hierarchy of six levels (Table 4) and a structural
classification system. The purpose of the hierarchy is to define and standardise structural and
floristic map unit information, provide a framework for quality control and assurance of vegetation
description information and generate outputs at various levels (eg. map products).
The NVIS Information Hierarchy (ESCAVI, 2003) has been adopted by NRETA Land and
Vegetation to map and describe vegetation communities in the NT. A database has been built to
accommodate this (refer to Chapter 7.3). A large amount of historic NT vegetation data has been
translated into the NVIS classification system. Future vegetation mapping should adhere to the
NVIS classification system.
Northern Territory Guidelines and Field Methodology
for Vegetation Survey and Mapping
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