Abstract
Allosyncarpia ternata S.T. Blake is a large tree endemic to a small area (25 000 km2) in the "Top End" of the Northern Territory, Australia. Within this area, A. ternata dominates the canopy in a variety of topographic settings and vegetation types, from closed-canopy rainforest in ravines to low woodland on cliffs and hilltops.This study examines some of the differences in A. ternata plants at micro-climatically contrasting sites in the Baroalba Springs - Koongarra Saddle area in Kakadu National Park. At cliff and hilltop sites, trees were generally shorter and more frequently multi-stemmed than trees on the ravine floor. These differences were associated with site differences in dry-season water availability, and were accompanied by differences in stomatal conductance, leaf xylem potential and leaf solute potential. Site differences in leaf characteristics and leaf assimilation rates were typical of sun vs shade leaves and were probably related to the average irradiance experienced during growth.
Allosyncarpia ternata's ability to occupy such a variety of habitats is probably due largely to its plasticity in leaf characteristics and tree physiognomy, which maintain photosynthetic activity under variable light conditions and throughout seasonal drought. This wide ecological amplitude, together with the plant's evident success in urban plantings, suggests that A. ternata adults and "established" seedlings have the physiological capacity to occupy a larger part of the continent than they do at present.
Dispersal and germination of A. ternata seeds, and the establishment, growth and survival of seedlings, were monitored in Allosyncarpia forest over a five-year period. Field and shadehouse trials demonstrated that "young" seedlings (i.e. those without a substantial lignotuber) are extremely vulnerable to drought and fire. It is speculated that, although habitats suitable for A. ternata might exist elsewhere in the Top End, the species is unable to disperse to them.
| Date of Award | Feb 1998 |
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| Original language | English |
| Supervisor | Derek Eamus (Supervisor) & Gordon Duff (Supervisor) |