The nitrogen fixing biota of Macquarie Island are dominated by cyanobacteria growing epiphytically or symbiotically with plants or lichens. Highest rates of acetylene reduction (N-fixation) were found in the leafy lichen Peltigera sp. Colonising herbfields and short grasslands, and in the coastal angiosperm Colobanthus muscoides. Significant rates of N-fixation were also associated with the ... liverwort Jamesoniella colorata commonly occurring in coastal and plateau mires, in a moss-bed of Dicranella cardotii colonising a land-slip face on the grassland slopes at 100m altitude, and within polsters of the mosses Ditrichum strictum and Andreaea sp. found in exposed localities on the plateau at 200-300m altitude. It was concluded that the common feature of plants supporting active N-fixation in dry habitats was the dense packing of stems and leaves, enabling water translocation to the cyanobacterial zone by wick action. Epiphytic cyanobacterial fixation in wet habitats was widespread and not restricted to plant species.
This work was published in Polar Biology, 11: 601-606.