The forest ecosystem assessment provides an analysis of information to determine whether viable examples of forest ecosystems are maintained throughout their natural ranges, and whether ecological processes and the dynamics of forest ecosystems are provided for in their landscape context. The assessment contributes to an evaluation against the proposed national reserve criteria, particularly criteria (1), (2), (3), (4), (5) and (7), and complementary off-reserve management as part of ecologically sustainable forest management (ESFM).
To meet these objectives the following assessment outputs are required:
maps of both the current and pre-1750 distributions of forest ecosystems;
determination of the current reservation status for forest ecosystems;
a description of forest ecosystems which are endangered, vulnerable or rare;
identification of refugia for flora and fauna; and
a description of disturbances and management actions relevant to forest ecosystems and refugia.
4.1.1 Ecological Vegetation Classes
Ecological vegetation classes (EVCs) are the basic mapping unit used for forest ecosystem assessments, biodiversity planning and conservation management at the regional scale in Victoria. The concept of ecological vegetation classes (EVCs) was introduced and used in the Old growth study of East Gippsland (Woodgate et al. 1994).
EVCs are derived from underlying large scale forest type and floristic community mapping. Floristic, structural, and environmental attributes are used to define EVCs. The relationship of each EVC to floristic vegetation communities and floristic sub-communities sensu Forbes et al. (1981) and forest types (Land Conservation Council studies) is discussed in Woodgate et. al. 1994.
A description of the methodology used to derive EVCs may be found in Commonwealth and NRE (1996), Appendix G.
Most EVCs within the study area have already been characterised in the LCC Melbourne 2 Study Area report (LCC 1991) and these are largely confined to the forested public land of the Great Dividing Range and the associated foothills. Descriptions of EVCs occurring in the Central Highlands is given in Appendix C. On the adjacent foot slopes of the Great Divide and on the plains beyond, only the less fertile habitats have remained substantially intact. Those EVCs which have not been previously identified in the study area (because they were confined to private land), or those requiring more characterisation are described in Appendix D.
4.2 Pre-1750 extent of Ecological Vegetation Classes
EVCs have been mapped on all public land in the Central Highlands region at a scale of 1:100 000. For the purposes of this assessment the pre-1750 extent of each EVC on both private and public land needed to be mapped to allow a comparison of the extant distribution and area of each EVC with that estimated prior to European settlement within the region.
New EVCs/complexes which have not been recorded in the previous public land vegetation mapping of the study area (Appendix D) occur either on fertile lowland plains or rolling hills which have been largely cleared for agriculture, or they occur on less fertile areas that have been subsequently been cleared for urban development on the fringes of Melbourne
In cleared or heavily disturbed areas, existing remnant vegetation and a variety of physical environmental attributes were employed to map the estimated pre-1750 extent of EVCs. This process relied heavily on subjective assessments by experts with extensive field knowledge of the area surveyed and the vegetation mapped. The attributes used to predict presence were specific to each EVC being mapped. Table 4.1 shows the attributes used, listed in their order of importance for each EVC. Further EVC attributes are presented in Appendices C and D. Table 4.1 describes the attributes used for those EVCs that occur on private land in the region.
Table 4.1: Physical attributes used to model and map the pre-1750 extent of EVCs.
In the time since the EVCs were mapped in the Central Highlands for the LCC’s Melbourne Area District 2 Review, the names for some EVCs have been updated in order to be consistent with the Statewide typology for EVCs. Table 4.2 provides the current names and synonyms from the previous LCC mapping.
Table 4.2. LCC Melbourne 2 Study EVC names and current EVC names.
Note: * incorporated in Floodplain Riparian Woodland
The inherent reliability of mapping produced at 1:100 000 scale using current technology is adequate for the assessment. However the certainty of this mapping is related to the quality of the underlying data sets used to define the vegetation boundaries.
Table 4.3 outlines the regional reliability of mapping of pre-1750 vegetation in Central Highlands against three categories:
High reliability: EVC mapping used both geological and topographic data which were available at 1:100 000 and or complete field checking;
Moderate reliability: EVC mapping did not use geological or land system data, relying on topographic data (eg. aspect or elevation) which were available at the presentation scale of 1:100 000; and or extensive field checking;
Low reliability: EVC mapping used land system and/or geological mapping which was only available at 1:250 000. The definition between important attributes (eg. fertility) was inadequate and map units in general were poorly registered to base features such as rivers and roads. Alternatively the area was modelled and required the use of coarse information or was not accessible for field checking.
Table 4.3 Pre-1750 EVC and mapping reliability.
EVC mapping north of the Yarra (all areas field checked)
EVC mapping south of the Yarra (extensive field checking)
EVC mapping in reservoirs (poor access and no contour information) eg Cardinia Reservoir
EVC mapping on the Yea spur (little remaining vegetation and poor access, but remotely field checked)
EVC mapping just west of Neerim South (poor access combined with complicated and ecotonal vegetation patterns)
EVC mapping north west of Labertouche (narrow private land area, poor access combined with complicated and ecotonal vegetation patterns)
The results of the Pre-1750 EVC analysis are presented in Table 4.4. These data have also been used to ascertain the rarity and threatened status of EVCs within the study area.
The extent of representation of EVCs in both conservation reserves and in parts of the State forest Special Protection Zone (SPZ) has been used as the basis for evaluating the current reservation status of forest ecosystems in the region.
The SPZ includes the following sub-categories of protected areas:
(a) Mostly large and contiguous areas designed for conservation of specific values and with boundaries based on reserve design principles;
(b) A network of connecting areas (200-400 m width) based around riparian zones (including Heritage River corridors) but also including wildlife corridors on ridges and crossing between catchments;
(c) Narrow linear reserves of less than 200 m width and small areas less than 5 ha; and
(d) Areas protected by forest management prescriptions. These include all permanent streams and all rainforest stands plus adjacent buffers of at least 20 m width, and all heathland EVCs plus a buffer of at least 40 m.
Table 4.4 : Representative conservation (percentage reservation status) of EVCs in the Central Highlands study area based on Pre-1750s vegetation mapping.
Percent of EVC (pre-1750 extent) in each land category