Managing unwelcome environmental events when they occur, such as tree decline, requires a clear understanding of the spatial and temporal distribution of the event.  Wandoo has been extremely difficult to identify and map from aerial photographs and early distribution maps were prepared by ground survey.

The WRG developed a method of rapidly and consistently assessing crown condition in wandoo. The two parts are:

1. remote sensing e.g. aerial photographs, Landsat, airborne thematic mapping; and
2. ground survey e.g. photo points, plots, road reconnaissance, visual assessment along transects.

Remote Sensing

In 2004, CALM and CSIRO undertook a project to assess wandoo canopy decline at landscape scales using a process known as Landsat Trend Analysis.  This project aims to:

• map the distribution of wandoo decline and recovery at various sites using remote sensing technology; and
• identify changes in vegetation cover from 1988–2005 using trend analysis of Landsat imagery data.

Sites within Helena catchment (State Forest and Talbot Block), Julimar Conservation Park (and Drummond Nature Reserve) and Dryandra Woodland Reserve were examined for changes in canopy cover between 1988 and 2005, using Landsat Thematic Mapper^TM. The proportion of declining, recovering and stable wandoo canopies at each site was assessed and trend analysis maps were produced using Vegmachine (CSIRO) software. Field investigations helped confirm the accuracy of the data to predict tree decline events.

Trend analysis indicates that although crown decline in wandoo is still occurring at a number of locations, recovery of wandoo crowns from epicormic growth is also evident.  Over most areas, wandoo canopies appear to have been stablised over the last few