6 - The climate theory I. Water stress

Summary

Schimper's (1903) original use of the term ‘rainforest’ succinctly encapsulated his belief that luxuriant, Xoristically and structurally complex tropical vegetation could only develop in a drought-free climate. Although some Australian ecologists have adhered to the idea that moisture supply is of critical importance in controlling the distribution of Australian rainforest (Specht 1981a), there are several features of Australian rainforests that are inconsistent with this theory. Firstly, there is an imperfect correlation between high rainfall areas and the distribution of rainforest, a fact that puzzled pioneering ecologists such as McLuckie and Petrie (1927). Secondly, in the latter half of this century many Australian ecologists broadened the concept of rainforest to include vegetation that occurs in low rainfall and seasonally dry climates (Webb 1959; Baur 1968; Webb and Tracey 1981; Adam1992) (Figure 6.1). This broadening of definition is reflected in the use of the oxymoron ‘dry rainforest’ (Baur 1957; Adam 1992; Fensham1995). Indeed, many authors have opted to spell rainforest as a single word (rather than the more conventional ‘rain forest’) in order to play down the implication that high rainfall is critical in controlling the distribution of rainforest in Australia (Baur 1968; Webb and Tracey 1981; Adam1992). Thirdly, there is evidence that some Australian rainforest trees, including some that occur in high rainfall environments, are extremely drought tolerant, being able to endure seasonal moisture deficits with ‘leaf water potentials more commonly associated with arid environments’ (Yates et al. 1988).