Program C Student Profile

Ingo Heinrich

Dendroclimatology of Australian Red Cedar

Supervisors: Dr John Banks

The project aims to:

1. Develop tree ring chronologies using Australian Red Cedar, a deciduous rainforest species;
2. Identify relationships between tree rings and instrumental climate records;
3. Derive annually resolved climate proxy data.
4. Examine the atmospheric CO2 fertilizing effect on tree ring increments

Study Species: Australian Red Cedar (Toona ciliata M. Roemer) can be found naturally throughout the tropical and subtropical rainforests from approximately 16º S to 34º S. T. ciliata produces a new flush of leaves in September and sheds them, depending on the latitudinal location of the site, between April and July. Trees at 4 sites were sampled covering the whole latitudinal range of the species.

Wood Anatomy: The wood of T. ciliata is semi-ring-porous. Growth rings are clear and delimited by large early season vessels and initial parenchyma cells also surrounding the vessels. Late wood vessels become smaller in diameter, the lumen of the fibre cells decreases and the width of their walls increases. The initial parenchyma cells store large amounts of starch grains, which are also visible in ray cells.

Dendroclimatology: So far, site indices for the Atherton Tablelands and Kangaroo Valley have been established. The Atherton Tablelands and Kangaroo Valley stands are separated by approximately 3000 km. The stand structures are different: mature rainforest in Atherton and open regrowth forest in Kangaroo Valley. Surprisingly, despite differences in stand structure, latitudinal distribution and climate the site indices (1963-2000) show clear similarities, e.g. a depression in the 1970s and a high in 1990. This strongly suggests that at both sites tree growth is controlled by the same factors. Annual tree growth in the Atherton stand is positively correlated with monthly rainfall in October to November and March to June. Tree growth is poorly correlated with rainfall in December to February, the cyclone season. During this time 75% of the annual cyclones occur. Cyclones are associated with excessive rainfall, tree damage and extended periods of cloudiness. Tree growth in the Kangaroo Valley stand is positively correlated with rainfall in January to March.

Conclusions: The correlation patterns indicate that rainfall alone does not fully explain the variation in tree growth. Rather, a multifactorial complex is responsible for limiting tree growth and is currently being investigated to identify environmental factors controlling growth of T. ciliata. Potential factors are temperature, humidity and soil moisture.