Dr Louise Cullen - Adjunct Research Associate

School of Plant Biology (M090)
University of Western Australia
35 Stirling Highway
Crawley  WA  6009
AUSTRALIA

telephone     +61 8 6488 3445
fax               +61 8 6488 7925
email            louise.cullen@uwa.edu.au

BSc (Hons), Victoria University of Wellington, NZ (1996)
PhD (Forest Ecology), Lincoln University, NZ (2001)

As of Feb 2007, Louise will be residing in Waikato, New Zealand.  She is still contactable on her UWA email address (above).

Background

My Hons research at the Victoria University of Wellington (New Zealand) examined the role of environmental factors in determining patterns in community composition of alpine wetlands in New Zealand. I subsequently moved cities and research directions, undertaking a PhD at Lincoln University (New Zealand). My PhD examined the relative roles of disturbance and climate warming in driving the dynamics of Nothofagus (beech) treelines. After being awarded my PhD in early 2001 I spent several months travelling in Australia and Europe and then worked as a consultant for an environmental science and landscape design consultancy in Perth. I joined the Ecosystems Research Group in 2003 as a postdoctoral researcher.

Research interests

• Water relations and ecophysiology of Callitris (Cupressaceae)
• Hydraulic architecture
• Stable isotope ecology
• Dendrochronology and past climates in Australia

Gully sites in the Pilbara region of north-west Australia where Callitris glaucophylla is protected from fire.

Current projects

(1) Drought tolerance and water use of Callitris glaucophylla (Cupressaceae) in the Pilbara, Western Australia

Callitris glaucophylla is widespread in arid and semi-arid Australia; however, the physiological mechanisms of drought tolerance of C. glaucophylla are poorly understood. To examine how C. glaucophylla copes with extreme environments we are measuring a number of inter-related components that reveal adaptations to drought, including:

• Instantaneous gas exchange measurements;
• Stable carbon and oxygen isotopes of foliage;
• Sap flow in roots and stems using heat pulse techniques (Burgess et al. 2001);
• Water potentials and relations;
• Osmotic adjustment as inferred from measurement of osmolytes; and
• Assessment of use of water sources using water isotopes.

Most of these measurements are made on seasonal basis to capture variation in gas exchange, plant water stress, isotope and osmolyte composition, rates of sap flow and transpiration in response to strong seasonal changes in water availability.

(2) Use of stable isotopes of tree rings of Callitris glaucophylla to infer past rainfall in the Pilbara, Western Australia

Using tree rings to generate high resolution data on past environments or climates has received relatively little attention in Australia. Callitris glaucophylla is one of the few trees in mainland Australia that has reasonably clear annual growth rings and we are currently developing stable carbon and oxygen isotope chronologies for trees in the Pilbara. Part of this work is testing whether cellulose extraction methods are necessary prior to isotope analysis, or if untreated wood retains as strong a climate signal. We expect to find strong relationships between isotopes and measures of water availability. 

Callitris glaucophylla with pollen cones

The principle of cross dating tree rings.

Selected publications

Cullen, L.E.  and P. Grierson (2007) A stable oxygen, but not carbon, isotope chronology of Callitris columellaris reflects recent climate change in north-western Australia Climatic Change 85, 213-222

Cullen, L.E. and P. Grierson (2006) Is cellulose extraction necessary for developing stable carbon and oxygen isotopes chronologies from Callitirs glaucophylla? Palaeogeography, Palaeoclimatology, Palaeoecology 236 206-216. PDF (288kb)

Cullen, L.E. and C. Macfarlane (2005) Comparison of cellulose extraction methods for analysis of stable isotope ratios of carbon and oxygen in plant material. Tree Physiology 25: 619-625. PDF (101kb)

Cullen, L.E., Duncan, R.P., Wells, A. and G.H. Stewart (2003). Floodplain and regional scale variation in earthquake effects on forests, Westland, New Zealand. Journal of the Royal Society of New Zealand, 33(4): 393-701.

Dickinson, K.J.M., Chagué-Goff, C., Mark, A.F. and Cullen, L.E. (2002) Ecological processes and trophic status of two low-alpine patterned mires, south-central South Island, New Zealand. Austral Ecology, 27: 369-384. 

Cullen, L.E., Stewart, G.H., Duncan, R.P. and J.G. Palmer (2001) Disturbance and climate warming influences on New Zealand Nothofagus treeline population dynamics. Journal of Ecology, 89: 1061-1071.

Cullen, L.E., Palmer, J.G., Duncan, R.P. and G.H. Stewart (2001) Climate change and tree-ring relationships of Nothofagus treeline forests. Canadian Journal of Forest Research, 31: 1981-1991.

Useful links

The Ultimate Tree-ring Web pages
Tree-ring Society
Learn how to cross-date online
Todd Dawson' lab webpage