Annual Growth Rings and Growth Zones in Woody Plants in Southern Australia

Abstract

Cross sections of 760 trunks of approximately 670 species from 47 families of shrubs, dwarf shrubs, and trees were examined to study the incidence and appearance of different categories of growth zones. In montane/alpine sites with relatively cool winter temperatures all the woody plants form distinct growth rings similar to those seen in boreal and temperate regions throughout the world, and thus these rings are considered to represent annual rings. Most species from this phytogeographical zone are useful for crossdating. In the savannahs, the jarrah and karri woodlands of the southwest and the subtropical rain forests of the southeast identifiable growth zones are formed in most species. The approximate age of the woods can be determined, but crossdating is difficult or impossible. In the desert areas woody plants form irregular growth zones, the number of which may correspond to the incidence of rainfall, and age determination and crossdating is mostly impossible. Members of the well-studied families Cupressaceae, Epacridaceae and Myrtaceae form growth zones that are more distinct than the Mimosaceae and Proteaceae. Included phloem is present in all Chenopodiaceae, one Loranthaceae and two species of Verbenaceae.