The root and shoot development of Eucalyptus regnans F. Muell

Abstract

During the first season, E. regnans develops a fairly strong tap-root, and later commences to produce a system of laterals. Seedling shoot growth is slow at first but increases rapidly. In the sapling stage, sinker roots develop from the laterals which extend far beyond the crown. Growth in height of the tree is very fast. During the pole stage, the conical crown is well developed, sinker roots become branched and the tap-root dies back. In the spar stage, the crown approaches maximum height and expands greatly. The sinker and lateral roots become very well developed. During the long mature stage, the fully elevated crowns become open and commence to die back. Buttresses are prominent and a complex system of sinker roots is present. Overmaturity is marked by a very large trunk epicormic growth and progressive die-back of the central area of both crown and roots.

On warmer and drier aspects the root systems of seedlings and pole stage trees appear to be less well developed than on the cooler and moister aspects. On steep slopes, the root systems of pole stage trees may develop asymetrically. Layering of prostrate trees may occur on southerly slopes and root fusion between trees is relatively common. In swamps, vertical roots are short and trees are very unstable.

Pornaderris aspera, one of the more common understorey species, develops a shallower and less spreading root system than E. regnans. In the early stages the lateral roots of both species are shallow and occupy the same soil zones; competition for moisture and nutrients is therefore likely to be very intense.