B is for Buttongrass

Three days!”  Stuart, one of the regular Melaleuca pilots, shook his head in amusement.  “When this fella said he was doing a three day course on buttongrass,  I couldn’t believe it.  But when you look a bit closer, you realise how complex it actually is.”

Buttongrass moorland dominates much of the wet, poorly-drained country in the Tasmanian Wilderness World Heritage Area. To me, buttongrass (Gymnoschoenus sphaerocephalus) has always looked like it’s throwing a party, its spherical flower-heads like tiny round champagne corks, exploding from the tussocks on elegant stalks. But don’t be fooled – there’s a lot going on beneath this sedge’s cheery facade.

Around Melaleuca, the moorlands are riddled with the chimneystack-esque burrows of burrowing crayfish. It’s thought that buttongrass and the crayfish have a symbiotic relationship – the crayfish dig their homes into the root systems of the plants, which provide them with both shelter and food – buttongrass rhizomes are edible.  In return, the burrows improve aeration in the often-waterlogged soils.

As well as being poorly drained, the soils underlying the buttongrass are also strongly acidic.  At a pH of 4.5, they’re roughly on par with beer, and have similar impacts on nutrient uptake.  Whilst beer may cause you to forget to eat enough to gain adequate nutrition,  a low pH in peat soils means that many valuable nutrients are less available to the local plants and animals.

Individual species have their own ways of dealing with these issues.  Carnivorous plants are common amongst the buttongrass, obtaining their extra nutrients from unwary insects. Burrowing crayfish shed their carapace (shells) annually, immediately eating them to conserve hard-to-get calcium.

Buttongrass doesn’t mind a burn, and unless the underlying peat soils are dry, individual plants usually survive a fire.   The critically endangered orange-bellied parrots rely on the periodic patch-burning of the buttongrass moorland vegetation – this leaves multi-aged stands of vegetation at varying stages of growth, hopefully providing enough seeding plants to keep the parrots’ appetites satiated.

The buttongrass moorlands of the Wilderness World Heritage area are also home to the Mysterious Mounds of Melaleuca.   Of uncertain origin, these raised, round lumps rise out of the moorlands like giant pimples.  No one is really sure how they were formed. The most popular current theory involves the influx of groundwater beneath the mounds, but for completely unscientific reasons, I prefer the one that is based on parrot poo.

As far as I understand it, this theory suggests that the parrots find a nice stick in the landscape to sit on, visiting it regularly and “enhancing the nutrient profile” of the soils beneath it.  This leads to increased plant growth, which can accumulate more soil, growing more plants to attract said parrots, forming a kind of poo-enhanced positive feedback loop.  As previously stated, my preference for this theory has nothing to do with its likely accuracy, and everything to do with my penchant for parrots.