Original story by Geoff Vivian, ScienceNetwork Western Australia
A LOCAL ecologist says aquatic plants in the Kimberley’s arid tropics have evolved to cope with harsh and unusual conditions.
Mr Cross is also studying the carnivorous aquatic plant Aldrovanda vesiculosa. Photo: John Pittman
University of WA PhD student Adam Cross gave the example of short-lived aquatic plants or ephemeral hydrophytes living in temporary pools called gilgai, on the black soil plains.
“The extensive alluvial mudflats crack and dry in the dry season, they form mounds and hollows,” Mr Cross says.
“In the subsequent wet season [they] fill with water and stay wet for months at a time.
“They will go from completely inundated throughout the wet season, and then within a very short period once the dry season begins they will dry down to completely desiccated rock-hard mud.
“They also burn with quite regular frequency as bush fires go through in the savannah areas of the Kimberley.
“Fire is an ecological mechanism for many species in Western Australia particularly, but not one which people would associate with the aquatic flora.
“Fire may play a role in the ecology of some of the ephemeral species.”
Mr Cross says Kimberley sandstone pavements are an even more ephemeral habitat for their water plants which show a high degree of endemism.
They complete their entire life cycles in pools as shallow as one centimetre, which may dry up just three weeks later.
He says some of the sandstone country dates back to the earliest periods in the planet’s history, and its aquatic flora may have survived the arid glaciation periods that caused significant extinction events among other northern Australian flora.
He is conducting PhD studies on the ecology of vegetation in Kimberley aquatic habitats, particularly hydrophytes, at Kings Park laboratories.
As such plants and habitats are inadequately described, part of his research examines ecological triggers to plant growth and seed germination.
“From the field observations … we can observe what naturally occurs; how the plants respond to periods of rainfall, how they respond to flooding, how they respond to drying,” he says.
“When we come back in the laboratory we can then run seeds through simulated natural conditions, and try and explore some of the logical mechanisms that maintain the ecosystem.”
These include subjecting soil and seeds to various tests to see whether important compounds evolve from wet soil, which may stimulate germination.
“It’s really all just about figuring out those ecological cues and building up the story of why the flora that’s in the Kimberley is there and what mechanisms have shaped the building of that diversity.”
Notes:
Adam Cross is a PhD student at the University of WA. He is based at Kings Park. He is lead author of the preliminary paper: Cross et al Ephemeral freshwater habitats and adaptations of the aquatic flora in the North Kimberley bioregion, Western Australia.
This story pertains to deliveries in theme 3 of the Kimberley Science and Conservation Strategy.
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