Orchids In Remnant Roadside Vegetation

This week’s post written by Leo Davis is an article (slightly edited) from The South Australian Naturalist 91 (1): 34 – 37 January – June 2017. In this article, Leo highlights the importance of  the role of roadside vegetation in preserving the native orchids and flora.

All photographs are by Leo Davis.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 OrcFig 1: Thelymitra antennifera hybrid

One of my rules of thumb is ‘If I am in a Conservation Park, I’m on ground that nobody could make a living from.’ One, usually more, of nutrient poor soils, excess salinity, extreme rockiness, steepness, poor moisture retention, low rainfall or even being waterlogged, will be a feature of the location. There are a few odd spots that have survived partly intact, that have good soil, sufficient rainfall, etc. These include cemeteries (The Nationally Critically Endangered ghost spider orchid (Caladenia (syn. Arachnorchis) intuta) holds on in a cemetery on Yorke Peninsula) or exclusion zones around water storages (including a reservoir reserve in Lobethal that the public can now access) or abandoned railway yards (including Sherlock, where so far I have found 21 species of orchids and part of a reserve in Halbury.)

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 2: Little Yellow Club Mallee Spider Orchid Caladenia (syn Arachnorchisverrucosa

When I go in search of plants with the Botany Group of the FNSSA (Field Naturalist Society of South Australia), or for orchids with NOSSA (Native Orchid Society of South Australia), or when I do surveys of threatened orchid species with DEWNR (Department Environment, Water and Natural Resources), or orchid seed collection with the Adelaide Botanic Gardens, or go on weeding parties to protect endangered species, the destination is always one of these deprived, rejected sites. The orchids I see are those adapted to or just hanging on in such sites. We never see orchids that lived on better soils, say on the Adelaide Plains. How many have become extinct?

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 3: Common Mallee Shell Orchid Pterostylis dolichochila

Wherever the land was suitable for agriculture it was clear felled. Almost nothing of the original flora and little of its associated fauna, were left. But there is a tiny flimsy exception. Crossing these highly productive agricultural zones are roads and sometimes these have remnant vegetation. For a person interested in orchids, these narrow strips are normally areas of slim pickings but occasionally finds are made. Near Halbury, the Nationally Endangered Halbury rufoushood (Pterostylis sp. Halbury or Oligochaetochilus lepidus) can be found in some roadside spots.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 4: Mallee Bearded Greenhood Pterostylis (syn Plumatichilos) sp. Mallee Bearded Greenhood

The most remarkable piece of roadside vegetation that I have come upon was discovered by and shown to me by Glenn Dean, the Environment Officer with the City of Murray Bridge. He found a section of predominantly broombush (Melaleuca uncinata) vegetation, only about 200 m. long, on the verges of a single car sandy track, east of Murray Bridge. It is so close to the vegetation that cars can be scratched. I have found 24 species of orchid (Glenn has found more) blooming there sometime between March and October each year. All images shown here (Figs 1–11) were made at this site. If the little used road was not there the land would have been under crop, being equal in quality to regularly cropped fields to either side, and is of much higher quality than any normally allocated to Conservation Park status. Most of the orchids found can indeed be found in some of the poor sites dedicated as Conservation Parks, including species similar to those found at Ferries McDonald and Monarto Conservation Parks with their poor sandy soils. But this spot, which for some reason supports species that do not grow just 100 metres east or west along the road, has such species as the Nationally Critically Endangered Mallee Leek Orchid (Prasophyllum constrictum) (Fig. 8), that requires soils as good as those demanded by wheat, so it is essentially doomed.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 5: Rusty Rufoushood Pterostylis biseta (syn Oligochaetochilus bisetus)

Its single plant sighting here is regarded as a ‘rediscovery’ of a species not seen for years. In the longer term I guess this tiny site of orchid species richness is in a transitory state and most species will disappear. The surrounding cropping land is neither a source of seed nor a suitable landing site for it and it provides damaging wind blown nutrients and other chemicals. So I will cherish it while it lasts and hope others appear, if only briefly. Here is a reminder, that most of you do not need, of the value of roadside vegetation (with the understanding that it can contribute to native animal mortality) and that we should manage, extend and guard its presence.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 6: Rufoushood Pterostylis (syn Oligochaetochilus) boormanii complex sp.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 7: Cinnamon Donkey Orchid Diuris palustris

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 8: Mallee Leek Orchid Prasophyllum constrictum

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 9: Limestone Tiny Shell Orchid Pterostylis cycnocephala
(syn Hymenochilus calcicolus)

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 10: Caladenia (syn Jonesiopsis) capillata x Pheladenia deformis hybrid

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 11: Small Rustyhood Pterostylis pusilla (syn Oligochaetochilus pusillus)


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