This layer contains identified areas of modelled old-growth forest derived from both vector and grid based analysis using disturbance data that post dates the source old-growth analyses.  Alpine Fire Severity Mapping (2003) and Logging history records that conflict with Old-Growth Forest (OG100) have been reclassified as not old-growth forest.  

Areas delineated as old growth forest are identified to meet the Victorian definition of old-growth forest based on a set of modelling criteria, rules and input datasets.  The data is not reliable at scales less than 1:100,000 (ie 1:25,000), not all old-growth polygons have been confirmed by field checking and the reliability of the modelled linework has not been verified.

This layer contains identified areas of modelled old-growth forest derived from both vector and grid based analysis using disturbance data that post dates the source old-growth analyses.  Alpine Fire Severity Mapping (2003) and Logging history records that conflict with Old-Growth Forest (OG100) have been reclassified as not old-growth forest.  

Areas delineated as old growth forest are identified to meet the Victorian definition of old-growth forest based on a set of modelling criteria, rules and input datasets.  The data is not reliable at scales less than 1:100,000 (ie 1:25,000), not all old-growth polygons have been confirmed by field checking and the reliability of the modelled linework has not been verified.

OG100 is a layer designed to store the major modelled output of old-growth forest studies for Victoria.  Modelled areas of old-growth forest are used as a major input into the preparation of Regional Forest Agreements and Forest Management Planning and associated analysis.  MOG2003 is derived from OG100 with harvesting history removed and modifications as a result of the Alpine 2003 Fire Severity mapping.

Precision:  +/- 200 m
Determination:  Deductive estimate based on 30m grid cell size used and precision of historic disturbance datasets used.

A preliminary estimate of attribute accuracy would be:
90% for polygons GT 10 hectares 
75% for polygons LT 10 hectares

The Old-growth forest modelling is based on a set of logic rules. All forest categories have therefore been determined consistently within each study area. Some logical anomalies may exist where the modeling has been unable to cope with exceptions to the logic rules. The data is not reliable at scales less than 1:100,000 (ie 1:25,000), not all old-growth polygons have been confirmed by field checking and the reliability of the modelled linework has not been verified.

Fire Severity Mapping and Logging history records that conflict with Old-Growth Forest (OG100) have been reclassified as not old-growth forest.

Dataset Source: Old Growth Forest modelling process for each old-growth forest studies including ; East Gippsland, Central Highlands,North_East, Gippsland and Otway-Midlands.  Areas shown in logging history up to July 2002 ( as at Dec 2003) and Fire Severity Mapping (Firesev-2003) have been removed from old growth as modelled in OG100.

Dataset Originality: Derived

                            
                              History: Original Old-growth forest projects undertaken during 1990-97, generating an output file called OG100, defining modelled old-growth forest across RFA areas in Victoria.  As a result of updated disturbance data inlcuding updated and modified logging history data, and also the Jan-Feb 2003 Alpine Fire Severity mapping classification (FIRESEV03), the impact on old-growth was identified as an issue.  MOG2003 is derived from OG100 overlayed with updated logging information and fire severity classes.  The fire severity class 1 (crown burn) impacts on all forest types, whereas class 2 (severe crown scorch) impacts on ash forest types only.  So old-growth forest in these classes was seen to be removed from the old-growth class, as was modelled old-growth with clearfell harvesting history.

Relationship to other Datasets: The old growth forest modelling process used to derive this layer uses key disturbance datasets, including GRAZE100, LOGHIST100, LOGHIST250, FIRE100_XY, AGCLEAR100 and mining layers, and vegetation attributes from the GSTAGE100, EVC100, SVEG100 layers.

Current Design Issues: The old-growth modelling process is undertaken on a study areas basis with which each study applying different rules and inputs.  It is possible that adjacent study areas within one tile may have edge matching problems.

Future Design Issues: The current dataset does not assign an accuracy level to any polygon.  This may need to be accomodated as areas of old-growth forest are increasingly verified in the field.

Related Documents: None

A Study of the Old-Growth Forest of East Gippsland, Woodgate et.al. 1994
Central Highlands Old-Growth Forest Project, Forests Service Technical Report 96-3
"Study of Old Growth Forest in Victorias Central Highlands", Forests Service Technical Report 96-3.
"Stand Class Definitions and Polygon Labelling Guidelines for the State Forest Resource Inventory". Peter Elliot, Department of Conservation and Natural Resources 1996
"Study of Old-growth Forest in Victoria's North-East", forest Service technical report 98-1.
"Old-growth Forest study of Gippsland Victora - Modelling of Old-growth Forrest Status". Study Report. Stephen Farrel & Milos Pelikan (Unpublished Report), 1999.
"Old-growth Forrest Study of South - Western Victoria: Portland Wimmera and Otways- Midlands - Modelling of Old-growth Forest status", Study Report. Stephen Farrell and Milos Pelikan (Unpublished Report), 1999.