A dendroclimatological investigation of Phyllocladus aspleniifolius (Labill.) Hook. f.

A network of fifteen Phyllocladus aspleniifolius (Celerytop Pine) chronologies for Tasmania, Australia, is developed. These sites effectively form north-south and east-west transects across the state, ranging in elevation from sea level to 850m above sea level. Crossdating is established between sites spread across the state, indicating the existence of a common broadscale control mechanism. The growth response to a number of climatic variables, including maximum and minimum temperature, precipitation, zonal and meridional indices, and the . Southern Oscillation Index is investigated. The most prominent features of the response functions produced for these variables are a consistency across sites in their response, especially so for northern sites, and a significant and negative correlation with prior growing season temperatures. High frequency variability in the quasibiennial range dominates the spectra of ring width series and is investigated in an attempt to determine whether it contains statistically significant climate information. Strong evidence for the influence of a climatic factor is not apparent, although the influence of the Zonal Index may be significant. Maximum temperature, the variable most consistently and most strongly correlated with ring widths, is used as the basis for climatic reconstruction on time scales greater than 2 years. Attempts to reconstruct climate by the more traditional technique of principal components regression were unsatisfactory, with insufficient variance due to climate being explained. Structural time series analysis is adapted for dendroclimatic reconstruction and some improvements in models result. The structural time series reconstructions show some differences between different regions of the state over the twentieth century which apparently did not exist in the previous century. While these reconstructions approximately trace the trend of increasing temperatures indicated by high altitude Lagarostrobos franklinii (Huon Pine) and instrumental records over the past century, there remain some significant differences in reconstructions from the two species. Different optimal temperatures for photosynthesis associated with elevational differences of sites are consistent with these differences. In large part, the limitations revealed through an examination of climate response of this species, and through the development of models for climatic reconstruction, relate to physiological questions concerning the species and point to a need for more detailed investigation of physiological aspects of species used for dendroclimatic work. Such investigations would allow a fuller utilisation of the potential offered by these species, and networks of them, as well as opening the way to a better understanding of resultant climatic reconstructions.