Australia: The Land Where Time Began

A biography of the Australian continent 

Nitrogen fixing in the Kwongan Sandplain Flora

There are many legumes present in the Kwongan flora, all carrying out nitrogen fixation. There are many leguminous shrubs among the communities of the Kwongan, adding an estimated 2-15 kg of nitrogen per Ha annually. The mineral requirements for nodule formation and nitrogen fixation are the likely limiting factors in such nutrient-deficient ecosystems. The infection thread of the fungi are known to require calcium, and they are believed to also require zinc and copper for their formation. Once infection has been accomplished, boron is required for vascular continuity and sugar transport between the nodule and the root.

A cycad growing in the banksia woolland of the Perth Coastal Sandplain, Macrozamia reidlei, has been found to add up to 19 kg/Ha/year to the soil. In some banksias, nitrogen-fixing cyanobacteria are present in the nectar produced by their flowers. Large-scale nectar production and different plants flowering at different times result in plenty of nectar being available in the Kwongan ecosystem throughout the year. The nectar being produced throughout the year is taken advantage of by the small mammals that are the pollinators, and co-evolved with the plants. It has been proposed that the nectar being available throughout the year suggests the advantages outweigh the energy costs, in such a nutrient-poor environment, less energy being required to make nectar than to make tissue. The nectar provision is necessary in large quantities to  maintain the pollinators needed to travel between widely distributed plants in a 'democratic society' such as the Kwongan. 

Sources & Further reading

  1. Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003
Kwongan Sandplain Flora, Western Australia
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                                                                                           Author: M.H.Monroe  Email:     Sources & Further reading