A secret native garden – Carnot Bay Mound Springs June 22, 2009Posted by kimberleyplants in SKIPA Excursions, wetland plants.
Tags: carnot bay, ferns, mound springs, trips, wetland plants
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Gaze across Carnot Bay’s blisteringly white salt marshes, pocked with dead tree stumps and tenacious herbs, and you will see an oasis of green – a mirage on the horizon. But this is no hallucination. It is an incredible freshwater jungle environment, surrounded by salt. It is the Bundabunda Mound Spring.
Mound Springs are dotted along the Kimberley coast, where freshwater close to the surface allows a unique environment to form on the marshlands. The water seeps out across the surface and over the centuries dense layers of vegetation have broken down to form a sloppy black peat in which ferns, trees and vines thrive. It is like a giant hydroponic garden.
Stepping into the thicket brought instant relief from the heat and glare of the salt marshes. It was dark and humid with filtered light, plenty of seedlings stretching for the canopy and mouldering logs. The breeze dissipated.
The black ground was spongy and it was like walking on a waterbed or a trampoline. This was beautifully demonstrated by Beau Bibby who jumped up and down and sent a shudder through the SKIPS group. You could see the vibration, like a pond ripple, through the ferns and up the tree trunks. The ground was so soft a stick was driven right through without effort.
The group trudged through soggy marshy ground, up to our waists in thick ferns. These ferns dominate the floor and on occasion the ‘walls’ of the thicket; Cyclosorus interruptus has tall narrow fronds, the Mangrove or Swamp Fern Acrostichum speciosum is leathery and large leaved, while the delicate Climbing Maidenhair Lygodium microphyllum drapes the trees in tangled curtains.
It was hard work pushing through the snaggle of vines and fronds, sinking into black holes of water or standing on a log only to find it crumbled beneath you. Although some members of the group enjoyed the bounciness and tried out the pillows of ferns for softness.
The whole ecosystem seemed unstable or fragile. Trees don’t have deep roots in this water garden and often succumb to rot and storms. In parts where the canopy had been opened up to the hot sunshine the stinking passionfruit weed had taken over. Beau Bibby said the Passiflora had increased fivefold in the past 18 years and formed a thick mat up to a metre deep. It was more harmful than the Climbing Maidenhair because it smothered native plants.
Another exotic that had infiltrated the mound spring was the Banana. Contained to a grove at one end of the spring, the Lady Finger banana was planted some years ago to provide fruit for families living nearby.
Often described as a “discreet vine thicket”, these mound springs appear lush and impressive jungles. But the vegetation community is simple and not very diverse. There are just two main tree species Timonius timon and Carallia brachiata. The Timonius had soft corky bark which looked like a crocodile’s back, and according to the Broome & Beyond plant book, its timber was used by Europeans to make ladders. A few Swamp Corkwood Sesbania formosa also grow and around the saline fringes of the spring were Melaleuca cajuputi and mangroves. Other mound springs are known to have Banyan figs and other ferns.
Again despite its lush appearance wildlife was minimal apart from the cries of Red tailed Black Cockatoos overhead and the buzz of mosquitoes in your ear. Beau said he has seen one water python on all his visits.
Care and management of these special freshwater springs is a grey area. While local indigenous families keep an eye on Bundabunda, there’s nothing official to tackle weed management and no monitoring of water levels. Isolation certainly provides protection – but even the damage caused by our visit was enough for Beau to say excursions should be limited to once a year.
Special thanks to Beau Bibby for leading the expedition and sharing his knowledge, to Phil Docherty, and to Rita & Charles Clements for giving SKIPS permission to visit Carnot Bay.