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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B3, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
INVESTIGATING THE DYNAMICS OF WANDOO CROWN DECLINE WITH TIME
SERIES LANDSAT IMAGERY
K. Zdunic® *, G. Behn? R. van Dongen *
? DEC, GIS Branch, 17 Dick Perry Avenue Kensington, Australia - (Katherine.Zdunic, Graeme.Behn,
Ricky.vanDongen) G dec.wa.gov.au
KEY WORDS: Wandoo, Landsat, Time Series, Vegetation, Wandoo Crown Decline
ABSTRACT:
In the forests of south west Western Australia dramatic declines in tree health have been observed in recent years. The species
Eucalyptus wandoo has exhibited loss of crown foliage in increasing stages of severity; this condition is referred to as wandoo crown
decline and can lead to death. Determining the extent and timing of these declines is difficult on the ground due to the large
distribution of E. wandoo and the observation of tree declines at a range of locations and dates over the last 40 years. Understanding
the distribution, severity and timing of these declines is essential to the identification of the causes of these impacts.
Investigation of time series Landsat imagery can inform on locations of crown foliage loss and the time periods these losses occurred
in. Applying a vegetation index to a 20 year sequence of imagery enabled periods of decline to be identified. Employment of trend
analysis of four date time series demonstrated the dynamics of wandoo crown cover. Comparisons of periods of decline with the
variations of cover density over the entire image sequence facilitated the identification of possible locations and timing of wandoo
crown decline impacts. Changes in crown cover observed by the imagery analysis were compared to field surveys.
1. INTRODUCTION
1.1 Motivation
Over the last forty years Eucalyptus wandoo (wandoo) crowns
have demonstrated varying losses in canopy initially on terminal
branches in some cases leading to death. This is described as
wandoo crown decline (WCD). The Wandoo Recovery Group
was formed in 2003 to research, map and communicate the
incidence of wandoo crown decline (Manning 2009). The
Wandoo Recovery Group and others (Whitford er al 2010,
Brown et al 1986, Mercer 1991, 2003, 2008) have done various
field assessments examining the severity and extent of WCD.
The geographic extent and access prohibit comprehensive
evaluation across the entire wandoo occurrence. Lack of
knowledge about the timing and spread of phenomenon makes it
difficult to understand and manage. These issues have
instigated the following questions:
1) Where does wandoo crown decline (WCD) occur?
2) In what time period does WCD occur?
3) Isthere recovery from the decline?
4) Isthe recovery to previous canopy cover?
Time series satellite imagery can be utilised to inform these
questions and improve understanding of WCD over the last 20
years across its mapped occurrence.
1.2 Eucalyptus wandoo
Eucalyptus wandoo is an iconic tree of the Western Australian
wheatbelt and is valued for its wood and form. It is endemic to
the south west corner of Western Australia extending 500
kilometres from Moora in the north to Mount Barker in the
south along medium and low rainfall areas, generally 350-
* Corresponding author.
1000mm (figure 1) (Caphill 1984). The tree can grow up to 30
metres high and achieve a girth of three metres, this reduces in
lower rainfall zones (White and Manning, 2005).
|
|
|
|
|
WESTERN
AUSTRALIA |
|
!
=
KULIN
7%, MT BARKER 39 E
7s,
“og 800 Se
isohyets (mm) TN
5 0 50 100
| Mapped Wandoo Occurrence
Kilometers
Figure 1. Locality of wandoo in south west Western Australia
