G. MATUSICK ET AL.
patterns between the affected (water-shedding) and unaffected
(water-gaining) may explain the strong contrast in woodland
canopy impacts. Trees in water-limited forest ecosystems are
highly dependent on soil type, slope, and drainage patterns
(Costa et al., 2008). We therefore hypothesize the cumulative
effects of long-term rainfall reductions (leading to dropping
groundwater levels), inadequate winter precipitation in 2010/
2011 (leading to inadequate soil recharge), and severe heat
conditions in February 2011(leading to high canopy water
stress) led to canopy dieback in the water-shedding E. gom-
phocephala woodland. During extreme periods of dryness,
eucalypts located on water-shedding sites, with low soil water
holding capacity are susceptible to rapid drying and dieback
(Pook et al., 1966). We suspect the neighboring unaffected E.
gomphocephala woodland, although transpiring more water,
receives higher rates of precipitation runoff and therefore is
capable of withstanding stressful summertime conditions.
Recent climate change modeling suggests that Mediterranean
ecosystems will exhibit a range of responses to future climate
changes (Klausmeyer & Shaw, 2009). Specifically, this model-
ing has predicted that E. gomphocephala-dominated ecosys-
tems from the study area north will contract, while areas south
of the study are expected to stay stable or expand (Klausmeyer
& Shaw, 2009). Observations from this study are able to con-
firm these modeled projections are correct for the study area.
Additionally, they provide important field evidence for how
future contractions in E. gomphocephala ecosystems may occur.
An accumulation of this type of data is required for field vali-
dation of modeling tools as well as understanding the cascade
of immediate, short- and long-term changes in ecosystem
structure and functioning following dieback (Ellison et al.,
2005). Ultimately, this information will be required to facilitate
mitigation strategies.
Acknowledgements
The authors would like to thank the West Australian State
Department of Environment and Conservation and the City of
Rockingham for their support.
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