Messmate & brown stringybark

Pull a strip of bark from a stringybark and you will understand the tree’s whole name in one motion. It comes away long, fibrous and stringy, in a way a smooth-barked gum’s bark never will, and it does not shed — it stays on, thickening year on year into a shaggy, deeply furrowed coat that a child can grab and peel like rope. Two species wear this coat over the Mount Lofty Ranges: messmate, Eucalyptus obliqua, and brown stringybark, E. baxteri, and between them they roof most of what forest still stands on the wet spine of the hills (Guerin et al. 2023).

They are not, strictly, locals. Both species’ main strongholds lie far to the wetter, cooler south-east — the tall forests of Victoria and beyond — and the Mount Lofty stands are outliers, cut off from that core range by a wide belt of country too dry for a stringybark seedling to cross. Botanists call a stranded population like this disjunct, and the Mount Lofty stringybarks are about as clean an example as South Australia offers: an eastern wet-forest tree persisting here in a hotter, more summer-arid niche than its relatives elsewhere will put up with (Guerin et al. 2023). Every stringybark on this ridge is, in that sense, a small living fossil of a wetter climate that once reached much further than it does now, holding an outpost on an island in a drying land, exactly as the ferns and small marsupials tucked into the same gullies are doing.

That shaggy bark doubles as fire insurance. Beneath the fibrous outer coat sits a dense strand of dormant buds, insulated from heat that would kill an ordinary smooth-barked tree outright, and it is that buried strand, not the bark, that lets a scorched stringybark break out in an even green fuzz along its blackened trunk within weeks of a fire passing through (Burrows 2013). If the fire is hot enough to finish the crown anyway, both species keep a second, underground account: a lignotuber, a woody, starch-and-bud-packed swelling at the base of the trunk that can throw up an entirely new stem from the ground up (Auld 2020). It is a forest built to expect fire as a regular visitor, not an aberration — hard leaves and rope-textured bark over a hidden double-entry ledger of buds, one under the skin and one underground.

What that ledger was not built for is a drought with no ending. In the mid-2000s, and again around 2018 and 2019, whole hillsides of stringybark browned and dropped their leaves, worst along the hotter, drier northern and range-edge stands, with a root-rotting soil pathogen implicated where the dieback ran deepest (Guerin et al. 2023). A tree stocked with buds for fire is not automatically stocked for heat and thirst stacked one on the other, year after year — and a species already living at the dry edge of what it can tolerate has less room than most to find out the hard way. Stand under a stringybark on a good day, and it looks like the oldest, most permanent thing in the forest. Read its bark, its bud strand and its recent dieback together, and it reads instead as what it actually is: a marooned survivor, doing well so far, in a spot that is asking harder questions of it than it has ever had to answer before.