TITLE:
Drought and Heat Triggers Sudden and Severe Dieback in a Dominant Mediterranean-Type Woodland Species
AUTHORS:
George Matusick, Katinka X. Ruthrof, Giles St. J. Hardy
KEYWORDS:
Eucalyptus Gomphocephala; Forest; Western Australia; Die-Off; Climate Change
JOURNAL NAME:
Open Journal of Forestry,
Vol.2 No.4,
October
30,
2012
ABSTRACT: Ecosystems in Mediterranean climate regions are projected to undergo considerable changes as a result of shifting climate, including from extreme drought and heat events. A severe and sudden dieback event, occurring in regionally significant Eucalyptus gomphocephala woodland in Western Australia, coincided with extreme drought and heat conditions in early 2011. Using a combination of remote sensing and field- based approaches, we characterized the extent and severity of canopy dieback following the event, as well as highlighted potential predisposing site factors. An estimated 500 ha of woodland was severely affected between February and March 2011. Tree foliage rapidly discolored and died over this period. In the af-fected portion of the woodland, approximately 90% of trees greater than 20 cm DBH were impacted, while in the adjacent unaffected woodland 6% showed signs of damage. Tree density in the unaffected area had approximately 4.5 times more trees than the affected woodland. Precipitation drainage patterns are thought to explain the difference between affected and unaffected woodland. Dropping groundwater levels, a relatively shallow soil profile, and extreme drought and heat in 2010-2011 are thought to predispose water-shedding sites to drought-triggered canopy dieback during extended periods of dryness. Tracking forest health changes in response to severe disturbance is an important key to deciphering past and future vegetation change.