The growth and distribution of Mallee-Broombush (Eucalyptus incrassata-Melaleuca uncinata association) and heath vegetation near Dark Island Soak, Ninety-Mile Plain, South Australia

Abstract

The growth of mallee-broombush (Eucalyptus incrassata-Melaleuca uncinata association) on the Buckingham sand was followed for 12 years after a fire. The nutrition of the stand was followed for 6 years. The observations are compared with those made on heath vegetation on the Makin sand nearby.

It is shown that at first the mallee-broombush grew more rapidly than the heath, probably because the soil had a slightly higher fertility status. After 8 years, however, the growth rate of mallee-broombush declined, whereas that of heath vegetation increased rapidly.

Evidence suggests that, since the structure of the mallee-broombush became more irregular as the stand aged, a higher evapotranspiration probably resulted, reducing the water available for summer growth.

In heath vegetation a more uniform structure was maintained with age, and when Banksia ornata seedlings explored the whole nutrient profile, the stand responded by increased growth.

The distribution of the two vegetations in southern Australia is discussed in relation to the recorded observations. The validity of the hypotheses postulated to explain the distribution patterns needs to be tested by thorough experimentation.