Australian Journal of Botany Australian Journal of Botany Society
Southern hemisphere botanical ecosystems
Table of Contents
Australian Journal of Botany

Australian Journal of Botany

Volume 62 Number 1 2014

Legumes from nutrient-poor ecosystems such as the Cape Floristic Region grow on variable P soils. We investigated legume adaptations to low P soils, and found that related legume species in nutrient-poor ecosystems can have very different strategies to ensure optimal mineral acquisition. Globally, the distribution of legumes in nutrient-poor soils may not rely on the same functional traits.

BT13207Spatial and temporal variation in damage and dieback in a threatened subantarctic cushion species

J. Whinam, J. A. Abdul-Rahman, M. Visoiu, M.-B. F. di Folco and J. B. Kirkpatrick
pp. 10-21

Dieback in the cushion Azorella macquariensis, on Macquarie Island was monitored for four years. Although damage from wind appeared responsible for most damage at any one time, a yellow dieback, with symptoms consistent with a pathogen, caused the most rapid dieback.

BT13223Genetic control of flowering in spotted gum, Corymbia citriodora subsp. variegata and C. maculata

Myralyn Abasolo, David J. Lee, Lyndon Brooks, Carolyn Raymond and Mervyn Shepherd
pp. 22-35

The benefits of translocating plants for restoration, forestry or other purposes must be balanced against the potential negative consequences from gene flow to natives, or the introduction of a weed. In Australia, concerns over the potential for gene flow from planted hardwood forests (mainly Eucalyptus spp.) have stimulated research to support forest policy, management and certification associated with plantations. This paper reports on the degree of genetic control in flowering of spotted gums (Corymbia spp.), the most widely planted hardwood genus in subtropical Australia, as asynchrony in flowering time may be one tool for isolating plantings.

Species richness is predicted to decrease with decreasing patch size and increasing isolationand; thus, habitat fragmentation is considered one of the greatest threats to biodiversity. However, this study did not find strong evidence for reduced species richness within smaller patches in any ecosystem type studied; instead, finding species richness decreased with increasing patch size in the open forest ecosystem across ecosystems. In fire-prone ecosystems, time since fire was not a determinant of species richness within the sites studied.

A trade-off between shade tolerance and growth in open conditions is widely believed to underlie the dynamics of humid forests. Our glasshouse and field data produced no compelling evidence that this trade-off differed significantly between subtropical rainforest tree assemblages native to basaltic (fertile) and rhyolitic (infertile) soils in northern New South Wales, although the fastest-growing species were found on basalt. There was therefore no evidence that the allocational costs of adaptation to infertile soils alter the relationship between growth rate and shade tolerance.

Seed dispersal is important for the persistence of plant species. Here, we investigated the amount of within-species variation in fruit morphology of a coastal species, and the effect this had on buoyancy. We found that fruits with larger aeriferous mesocarp layers had the greatest buoyancy, and therefore greater capacity for oceanic dispersal. Intraspecific variation that imparts greater buoyancy and promotes oceanic dispersal may facilitate range shifts and assist coastal species to persist through climate change.

BT13237Seasonal variation in the nitrogen nutrition and carbon assimilation in wild and cultivated Aspalathus linearis (rooibos tea)

Daleen Lötter, Emma Archer van Garderen, Mark Tadross and Alexander J. Valentine
pp. 65-73

Rooibos tea is a unique health-enhancing beverage made from a shrub-like bush that grows only in the Cederberg mountains of the Western Cape, South Africa. The area has a semiarid climate and infertile soils, which makes crop production challenging. Although both wild and cultivated plants are harvested, the research suggests that the wild rooibos plants are better adapted to overcome the harsh environmental conditions. In the light of the increase in aridity projected for the Western Cape of South Africa, the present results warrant further investigation into the physiological traits responsible for drought tolerance in wild rooibos plants.

Pimelea or riceflowers are ephemeral native plants that still cause serious outbreaks of cattle poisoning in Australian rangelands despite decades of research aimed at preventing this. Our ecological research included ways to germinate the deeply dormant seeds and found that gibberellic acid was very effective. Stimulating Pimelea seeds to germinate reliably means further research can now be done anytime without needing field-harvested plants.

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