Abstract
Tuart (Eucalyptus gomphocephala) is an iconic woodland tree, endemic to Western Australia, and is one of the few eucalypts able to dominate on calcareous soils. Unfortunately, less than one third of the original extent of the E. gomphocephala woodland ecosystem remains in existence today, largely as a result of clearing for urbanisation, agriculture and industry.
Equally disturbing is the extensive decline of the E. gomphocephala ecosystem within the Yalgorup region, south of Mandurah, from unknown but probably complex abiotic andlor biotic causes. The recently described species Phytophthora multivora was isolated from the rhizosphere of declining tuart and may be contributing to this decline.
A large collaborative, integrated research effort is focused on finding the cause(s) of this decline. Intensive ground-based studies are being used in conjunction with digital remotely sensed imagery and other spatially explicit datasets to aid establishment of research sites, map the spatial and temporal pattern of the decline with the major objective to find strong correlations with abiotic andlor biotic factors.
The historical trend in canopy cover of areas of E. gomphocepha/a woodland can be accurately determined across the landscape using medium resolution (25m) LandsatTM-derived satellite data. Areas of particular interest were 'ground-truthed' in the present study to enable establishment of field sites according to changes in canopy cover over a 17 year period. High resolution (0.5 - 1m) Digital Multi-Spectral Imagery (DMSI) was then acquired for these sites and trees and shrubs of interest located using a differential GPS system. Detailed canopy assessments, foliar analysis, soil analysis and injection treatments have been completed for each site. Correlations between indicators of canopy health and a range of established spectral indices were examined. Annual DMSI has been acquired to detect changes in E. gomphocepha/a canopy and patterns of decline within the landscape.
Results from this study will be presented.