Morphological Differences in Lignotubers of Eucalyptus intermedia R.T. Bak. And E. signata F. Muell. Associated With Different Stages of Podzol Development on Coastal Dunes, Cooloola, Queensland

Abstract

The sandmass at Cooloola comprises a series of overlapping aeolian dune systems that extend in age from the present back more than 100 000 years. Podzols are the dominant soils, forming a sequence from rudimentary through to giant forms, according to age. The lignotuber morphology of Eucalyptus signata and E. intermedia was examined within each dune system across the chronosequence, at sites in which most factors affecting plant growth (available soil water status, drainage, light, temperature, fire regimes, exposure to wind and/or salt spray) other than a declining soil nutrient supply were similar. Three lignotuber morphologies were identified: (1) a single-stemmed (SS) form; (2) a multi-stemmed (MS) form with stems originating from a lignotuber only slightly larger than a main stem; and (3) a multi-stemmed plate-like form (MSP) with individual stems separated and growing from a plate-like lignotuber. Multi-stemmed forms of the two eucalypts occur along the coastal margin and on the most nutrient- poor dunes; at all other sites single-stemmed forms are dominant. The most nutrient-poor site had only MS and MSP forms, whilst in sheltered areas the coastal margin had SS individuals. We conclude that in the Cooloola sandmass the development of multi-stemmed forms in both E. signata and E. intermedia may be induced by a variety of factors, including very low nutrient status, but the multi-stemmed plate-like form of E. intermedia is most likely a response to an exceptionally low nutrient supply.