Canterbury Botanical Society, Torlesse Foothills, 19th April 2015
Saturday’s trip was postponed to Sunday with spectacular results. Saturday was bleak but Sunday……. Starting at an artificial irrigation lake in the foothills of the Torlesse Range we explored the wetland remnant that survived.
Only recently fenced there is already a clear difference between the cattle grazed and ungrazed portions. We were expecting a fertile red tussock wetland similar to this one, but what we found was a low fertility sphagnum peat bog. Not only that but from out in the middle it became apparent that it was to some extent a raised bog being higher in the middle than at the edges. Sphagnum peat bogs are amazing, the water-holding and capillary action in the moss and peat defy gravity drawing water upward. Rush peat bogs are quite different. There’s not a lot to see in a peat bog in autumn and some of the interesting things my cameras aren’t up to so I can’t show them off.
It was still dominated by red tussock but with the lower fertility the tussocks were a lot smaller and mixed in with the usual rushes and sedges. The low fertility has kept most of the weeds out, and would also have largely kept the cattle out, although there were enough dung piles to show they had been just about everywhere.
Some of the weed patches were disturbing, particularly Juncus effusus (soft rush), J. ensifolius (iris-leaved rush) and centaury (Centaurium erythraea) as they appeared to be spreading but for the most part while weeds were numerous they were in low densities. Along with all the sphagnum there were patches of gems, a blue-flowered sun-orchid (Thelymitra), sky lily (Herpolirion novae zelandiae) neither flowering at this time of year. Along with the common spike sedge (Eleocharis acuta) there was the secretive slender spike sedge(E. gracilis) and a comb sedge (Oreobolus strictus). A daisy of the Celmisia gracilenta group, Nertera depressa, Gonocarpus micranthus, Centella uniflora and a rather lush patch of Hydrocotyle sulcata.
This wetland really needs some formal monitoring to track any trends with the weeds and it would in any case be interesting to follow the changes that will occur as it recovers from grazing, and any peaks in fertility originating from dung and urine patches.
On our way out we visited an extensive beech forest remnant that shelters the homestead and may have been left as a timber resource, although it is now sadly neglected and for the most part there are only black beech remaining with the podocarps: totara, matai and kahikatea having been cut-out. Most of the remaining trees predate European settlement putting them in the 200 – 500 yr old age range.
With quite a few on their way out, it may not be too long now before most of these remaining trees are gone.It will take direct intervention (planting and weed management) to restore this forest and keep the mistletoe going. With good management the combined grazed and ungrazed parts would be among the most significant forest remnants left on the Canterbury Plains at something like 20 – 30 hectares in area.
The black beech (Fuscospora solandri) are laden with yellow mistletoe (Alepis flavida) but oddly going through the gate into the ungrazed portion there are very few mistletoe. Large broadleaf (Griselinia littoralis) also demonstrate the age of the trees. From a foresters point of view black beech are a useful native timber but unlike their European and North American counterparts aren’t a species that coppices and are equally difficult to dry when sawn.
The broadleaf however will coppice if they can be protected from browsing mammals and with very durable timber can make some interesting post material, and yes we really do have a broadleaf tree called broadleaf, or you could use papauma. The high density of mistletoe in the paddock may be a by-product of the ease with which those pesky omnivores and carriers of bovine Tb, the Australian brush-tailed possum can be shot. This is something I’ve seen in many parts of the country where mistletoe abound in the remnant trees of farmland while being apparently absent from nearby ‘protected’ forests. Yellow mistletoe would probably be OK if the possum browsing habit wasn’t to repeatedly strip all the leaves until the bush fails to regrow.
In the ungrazed main block an abundance of tree, brush, climbing and creeping weeds makes it unlikely that the black beech can regenerate without help, although it was good to see a few seedlings and saplings of matai and kahikatea under the hawthorn and barberry.