The Role of Orchids

October is Orchid Month with the greatest number of species flowering throughout South Australia; so it is worth considering the role of orchids in the Australian bushland.  Hence this week’s blog is an article written by Belinda Newman, Western Australia.

Orchids: The Canary in the Coal Mine was published in the Friends of Kings Park magazine For Plants and People, Issue 70 p 22-24, 2010.  The article is both a good introduction to, and summary of, her 2009 thesis Orchids as Indicators of Ecosystem Health in Urban Bushland Fragments

Orchids: The Canary in the Coal Mine

Belinda Newman – Research Scientist BGPA

What could orchids and canaries possibly have in common?

Before occupational health and safety and ventilation systems were commonplace in the mining industry, a caged canary would be bought down to the coal seam by the miners.  Canaries are particularly sensitive to methane and carbon dioxide which made them excellent indicators for the build-up of dangerous gases.  A singing canary meant everything was fine, a dead canary spelt trouble and an immediate evacuation.

Although orchids can’t sing, they do possess a number of traits that make them sensitive ecological indicators.  The relationships that orchids have with their surroundings form part of a complex ecological web.  Orchids have specific relationships with mycorrhizal fungi, which they require both for germination of their dust-like seed and ongoing growth of plants in adulthood.  These fungi in turn rely on the appropriate soil moisture content and carbon sources.  Above ground, the majority of terrestrial orchids in the south west of Western Australia rely on pollinators for successful seed set.  For some orchids this plant-pollinator relationship has become so highly evolved that removal of the pollinator would spell the end of the orchid.  The pollinators also have specific requirements for habitat, appropriate food sources and nesting sites.  These above and below ground links to the ecosystem make orchids particularly sensitive to disturbances and changes in their surroundings.

The potential for orchids to be used as indicators of ecosystem health formed the basis of a study between Kings Park and Botanic Gardens and Murdoch University.  The coal seam was eleven urban reserves of varying condition on the Swan Coastal Plain.  The canaries were seven orchids common to Perth’s urban bushlands; the Carousel spider (Caladenia arenicola), Cowslip orchid (Caladenia flava), Pink Fairy orchid (Caladenia laitfolia), Pansy orchid (Diuris magnifica), Dark Banded Greenhood (Pteryostylis sanguinea), Purple Enamel Orchid (Elythranthera brunonis) and the Mignonette orchid (Microtis media).  Before it was possible to see which orchids made the best canaries, it was important to determine the health of each of the bushland sites.  A number of environmental variables were chosen that best reflected the health of the ecosystems.  Extensive surveys and analysis of species composition, plant functional groups against these environmental variables revealed a range of site conditions from close to pristine to highly degraded.  This provided the backdrop against which to determine the effectiveness of orchids as indicators through the measured responses of the orchid species.

Firstly orchid presence and abundance was measured across sites to determine if particular orchid species showed a preference for particular site conditions.  Diuris magnifica and Microtis media showed strong correlations and were most abundant in poor condition sites and Pteryostylis sanguinea showed strong correlations to sites in good condition.  While the abundance and presence of orchids appeared to correlate with site condition, we wanted to know what other aspects of the orchid we could measure as a means of judging the health of an ecosystem.

Successful seed set in plants reflects a healthy ecosystem and the reproductive success of the seven orchid species was investigated to determine the effects of declining site condition on seed set.  Pollination trials were set up to measure natural and artificial pollination events across all sites.  Widespread depression in pollination across all species and sites was found to be occurring, rendering seed set a poor measure of ecosystem health.

Investigations into the below-ground links orchids have with the ecosystem were undertaken by determining the presence and abundance of orchid mycorrhizal for the seven orchid study species across all sites.  Mycorrhizal distribution was found to be patchy within urban reserves and also revealed unoccupied niches capable of supporting orchid germination.  A greater abundance of Microtis media mycorrhizal at sites of poor condition supported earlier correlations of plant abundance at sites of poor condition.  The higher abundance of mycorrhizal symbionts for Caladenia arenicola at sites of very good condition also suggests its potential as an indicator species.

The study also looked at seedling growth in urban reserves.  This was the first time that biomass allocation in orchids has been investigated in light of ecosystem health.  In poor condition sites, Diuris magnifica and Caladenia arenicola increased growth effort to the above ground leaf. In sites of very good condition, these two species increased growth to the tuber to take advantage of being able to store starch as a result of both fungal and photosynthetic activity taking place.  Most importantly this shows a measurable change over a short period time.  Although it is effort intensive, planting orchid seedlings of a standardised size into the field may provide a useful and rapid measure of ecosystem health, much like caged canaries were used in the past.

This research into using orchids as an indicator species is the first of its kind and suggests that orchids can be used as an indicator of ecosystem health.  Future research will need to focus on the thresholds of the species identified as potential indicators in this study.  What aspect of the orchid’s ecology will give clear and repeatable data linked to ecosystem health?  Following the canary analogy, how long can orchids hold their breath? Future studies would need to focus on testing these thresholds.  The results of this study suggest that orchid presence and abundance, orchid growth and orchid symbionts can be used as indicators of ecosystem health, although work needs to be undertaken to refine the understanding of their response to specific disturbances.  This study provides a baseline for investigating the utility of orchids as indicators of ecosystem health in highly fragmented systems.  Perhaps orchids and canaries have more in common than first thought.


Help Save South East Austalia’s Unique and Threatened Orchids

Australian orchids are special but Australian orchids have been disappearing from our landscape.  Throughout the country individuals and groups are attempting various conservation methods to help save our orchids.  One such group is Dr Nouska Reiter and her team from Orchid Conservation Program, and arm of the Australian Network for Plant Conservation Inc

Dr Nouska Reiter is seeking to raise money for a conservation laboratory to cultivate threatened orchids for reintroduction into the bushland.  She has a month left; so for details about the project and on how to help, go to Help save South East Australia’s unique and threatened orchids!

Orchids and Fire

Bushfires are a part of the Australian landscape.  The effect upon people and animals can be devastating but what of their effect upon orchids?  In 2012, Mike Duncan published a report Response of Orchids to Bushfire, Black Saturday 2009 for the Victorian Department of Sustainability and Environment.

Page one is a good summary of the effects experience by the orchids in Victoria:

This project addresses general community concerns about the response of orchids to the 2009 bushfires, by documenting the range of orchid responses encountered across all fire affected areas.  The information presented in the report is the result of data synthesis and direct field observations from a variety of sources, collected during the two years since the fires.
The response of orchids to the February 2009 bushfires was diverse, spanning the spectrum from being killed by fire, to being totally dependent upon the fire to flower.  In this report, the spectrum of responses that were encountered have been divided into five broad categories.

1. Fire Killed Species
Populations of epiphytes (e.g. Sarcochilus australis) and terrestrials with shallow tubers (e.g. Thynninorchis huntianus) were killed by the intense fire front.  In some cases, these species are likely to recolonise by seed from nearby unburnt areas, but in other cases, these species may require conservation intervention to assist in their recovery.

2. Fire Sensitive Species
Species such as Pterostylis alveata and Corunastylis despectans appear to have been sensitive to the bushfire, showing a large reduction in emergence over the following two years.  Populations of these species are likely to recover naturally over a number of years.

3. Fire Neutral Species
The response of the winter and spring flowering Pterostylis species were generally fire neutral, with their flowering rates neither increasing nor decreasing in the two years since the bushfire.

4. Fire Stimulated Species
The flowering of many Caladenia, Diuris, Prasophyllum and Thelymitra species was strongly stimulated by the 2009 bushfire, creating spectacular patches of massed flowering in the fire-blackened landscape.  Similarly, many smaller genera (e.g. Pheladenia and Glossodia) also showed a strong increase in flowering in response to the bushfire, sometimes producing clumps of more than 20 flowering plants.

5. Fire Dependent Species
There are four species (Burnettia cuneata, Pyrorchis nigricans, Leptoceras menziesii and Prasophyllum australe) that are dependent upon fire to flower.  These species are able to survive for extended periods without flowering.  Stimulated by the occurrence of the 2009 bushfire, these four species flowered en masse during spring 2009 (and to a lesser extent in spring 2010); the first time most of these plants have flowered since each site was last burnt.
Four nationally threatened orchid species (Caladenia concolor, C. orientalis, C. tessellata, and Pterostylis chlorogramma) occur within the area affected by the 2009 bushfire.  These species are part of an ongoing monitoring program, and the collected data offers an opportunity to quantify the post-fire flowering response of these species.  The data showed that grazing had negatively impacted seed production in each species since the 2009 bushfire.  It would also seem reasonable to assume that similarly high levels of grazing have occurred to other orchid species during this period.  A reduction in seed production is an important concern to any orchid species, but it is of particular concern to fire sensitive species, as it will lengthen the recovery time for these populations.  A reduction in seed production represents a lost opportunity for species that are fire stimulated or fire dependent, in terms of achieving recruitment to a population.  Fire-affected populations of these species will require careful management to ensure that seed production is not compromised into the future.

To see the full report, click here .………


Cathy Houston

Conducted by the Conservation group of the Native Orchid Society of South Australia Inc. for the Department of Environment and Natural Resources.

Members of the Native Orchid Society of South Australia and two volunteers conducted a three day orchid survey of Messent Conservation Park, following a prescribed burn that took place in March/April 2011.

The survey in burnt areas was undertaken from Friday 9th – Sunday 11th September, inclusive. A maximum of eleven people took part, not all being present for the entire survey time. Participants worked in pairs (or threes if numbers dictated such) and conducted ramble surveys within very rough grid areas of about 500 meters square. Because of the size of the burn area and access difficulty, none of the internal area was surveyed. However, many habitats were covered and extrapolation could predict what would be likely to occur in these areas. Some other vegetated areas were visited as well. These included flats covered in rushes, or sedges and rushes, a 16 month old prescribed burn area, a Pink gum (Eucalyptus fasciculosa) rise, mallee woodland and a Banksia herb-land.

Observations were taken of species present, numbers and any other detail of note, together with GPS location. A numbering code was used for most species.

The results were somewhat variable, presumably dependent on habitat types and their orchid population prior to the burn, the temperature of the burn and to a lesser extent, the emergence or otherwise of orchids prior to the time of burning. For instance, only one small population of Corunastylis (Genoplesium) was noted, this being a species that would have been flowering at the time of the burn. Similarly, no Eriochilus were observed in the survey area. However, Leporella fimbriata which emerges at a very similar time was present in some very large colonies.

The most abundant orchid by far was Pyrorchis nigricans. It was encountered in nearly all habitats of the survey area, the only exception being limestone ridges where it rarely appeared. Flowering had been promoted by the burn with perhaps about half the population in flower/going to flower. Density of the population fluctuated but it seemed to be consistently present. However, its absence was noteworthy from an area of burn undertaken in May 2010. The habitat was ideal for the species and given the proliferation throughout the 2011 burn one would have to speculate about the timing of that burn on that (and perhaps other) species. Very few species were located in that area at all. It has to be said in fairness though that the only Thelymitra epipactoides found in any burn area was seen in this 16 month old burn.

Perhaps the most orchid-rich habitat with regard to number of species was the limestone ridges. Some of the open flats had the least diversity. It was not easy to ascertain what the dominant vegetation had been in these areas. Conversely some of the flats had a good scattering of orchid species, the numbers of each being relatively low.

Winter flowering species were conspicuous by their low representation.  No Bunochilus (Pterostylis) were seen, few Urochilus (P.) sanguineus, Diplodium (P.) dolichochilum, Acianthus pusillus, Corysanthes (Corybas) species and Cyrtostylis robusta were seen in the burn area.  The only exception was Linguella (Pterostylis) sp. Mallee. It was encountered in small to medium sized colonies throughout the area, usually with a reasonable number of capsules developing. In a vegetated location Diplodium species was seen in good numbers.

Threats to orchids were minimal. Rabbits were present in noticeable numbers along the northern boundary. Similarly, there was some weed incursion along the northern boundary, Capeweed and one other being the main ones seen. Some predation was observed within the burn area, but nothing we would consider notable. Rabbit activity was also very evident in a flat/Pink gum rise on the track leading south to the boundary. Deer prints were observed throughout the areas we covered. A small flock of sheep encountered in the north eastern sector is of concern. They had free access to the park via a “kangaroo door” under the boundary fence, something they negotiated with ease when disturbed by a vehicle.

Species of significance were Thelymitra matthewsii and T. epipactoides, these both being nationally threatened species. Historical records existed for T. matthewsii from this park, but it had not been observed for decades, despite intensive searches having occurred following the 2002 burn. Some of this surveys records bear a similarity to historical records but since the latter were recorded prior to accurate global positioning systems it is uncertain about the actual locations. This species was encountered as mainly individual plants in about six different locations, usually in very low numbers. Some plants were just leaf but others were seed capsules. All but one group were located in burn areas, the species being very difficult to observe without the removal of much vegetation. It was noted that some of the area where the species was seen had been slashed. It was felt this could be beneficial to them. Observations in the lower South East seem to reflect this type of disturbance is beneficial to T. matthewsii and Thelymitra in general.

More than 60 plants of T. epipactoides were located in one area of a few hundred meters squared, with the exception of the aforementioned one plant in the 16 month old burn. Despite searching of hectares of similar sedge/rush-land, no others were located. Here again, it was thought that some random slashing of this habitat may benefit orchids that like the open areas, viz. Thelymitra, Diuris sp. Short tailed, Glossodia major, and some Caladenia species.
Present in low numbers on the limestone ridges was Arachnorchis (Caladenia) tensa, another nationally threatened species. Despite its national rating this species is more prolific in South Australia.

Another orchid that appeared in considerable numbers and most habitats was Arachnorchis (Caladenia) sp. South East. It grew as single or few plants right up to sizeable collections of plants, sometimes with up to about 50 in a group. Diuris sp. Short tailed was widespread and moderately common. Glossodia major was encountered as mainly single plants widely scattered. Caladenia carnea was in very high numbers under fairly dense mallee on the northern boundary. Microtis species when it was encountered, was in colonies with high numbers of plants. As a generalisation, Thelymitra were absent or in very low numbers. Exceptions to this were T. antennifera and T. benthamiana which were usually seen in very low numbers but widespread throughout the burn area. It was interesting to note that few of the latter were likely to flower, which contrasts with the 2002 burn when flowering was prolific.

One species promoted to flower by the burn was Prasophyllum elatum. It was widespread in most habitats, but not often in the flats. Plants varied tremendously in size and stature with some quite small plants flowering/going to flower. Predation of the leaves was relatively high, with nearly all being chewed down to between 100 to 150 mm. Buds were emerging from the open top of the leaf, instead of emerging from the side of an intact leaf. There were other Prasophyllum species present, but the survey was just too early to identify what these are likely to be. Most of these were found on the limestone ridges.

The orchid list held by NOSSA for Messent Conservation Park prior to this survey must have been somewhat limited because the number of species on our list has now been doubled. With the rediscovery of T. matthewsii in several locations within the park, the other two nationally threatened species present and the expanded knowledge of orchids within the Park we must consider this was a very successful survey. We thank DENR South East for making this survey possible.

An Eriochilus study in the Southern Flinders Ranges: 2010

R. Bates

Until  2009 when NOSSA did an orchid study of Wirrabara Forest Reserve the parsons bands or Eriochilus were thought to be rare in the Flinders Ranges, but that year Eriochilus were found all the way north to Mount Remarkable and were often seen as locally common.

In 2010 I did two visits, one in April and one in May to see how well they flowered after a wet spring the previous year.

Results: all colonies at Wirrabara flowered spectacularly in April 2010 but at Mt Remarkable flowering was poor.  No leaves were visible at the time.  The flowers were white with some strong colour and stems were quite bristly, see image. At Wirrabara plants were sturdy with up to four flowers per scape yet at Mt Remarkable plants were spindly and flowers mostly single.

It was thought that the reason for this difference lay in the wet spring of 2009 at Wirrabara with much less rain at Mt Remarkable.

The second visit in May showed a different picture. Very little rain had fallen at Wirrabara in autumn and the stems of all plants had hardly elongated.  Yet seed capsules were plentiful.  In contrast, Melrose near Mt Remarkable had received good autumn rain and stems there had doubled in length.

So it seems that the number of flowers and strength of plants depends on rain the previous season whilst height of stems depend on rain during the current flowering season.

Curiously, in both areas a second flush of flowering occurred in May with the second flush at Wirrabara producing tiny flowers on short spindly stems (see image) while those at Mt Remarkable had larger flowers on tall stems.

Flowers seen in both areas were similar in appearance and both had leaves which were large, apiculate, dark green, ribbed and hairy above, purple below.  Both the April flowered and May flowered plants belonged to the same taxon and clearly flower size and number, and scape length, are not useful in separating species as they are so variable.

On the other hand leaf shape, texture, ribbing and colour below are important in identifying the species as these are constant features.

Conclusions: only one species of Eriochilus occurs in the Flinders Ranges and this is the same as the common woodland species in the Mt Lofty Ranges.  This species has never been named officially but is generally known as Eriochilus sp Hills woodland and is best identified by it’s leaf … see image.

This is the most common of three or four Eriochilus species in SA.

Leaf of April flowering Eriochilus at Wirrabara dwarfing later May flowered
plants behind it.

Eriochilus species Hills near Mt Remarkable in May 2010

Surveying in the South East

Cathy Houston

In recent years a number of N.O.S.S.A. members interested in field work have been involved in surveys for orchids. These include surveys for individuals as well as government or semi-government organisations.

Late in March this year we undertook an Autumn survey of a forest in the South-East known as The Marshes.  As the name suggests the area is well served with swamps as well as forest of Stringybark with sandy soil.  Several members met the day before to check some areas in the upper SE.  Here in sandy-heath there were two species of Corunastylis in flower, often not very distant from each other, but each favouring different habitats.  In the heath were C. aff. rufa in flower and capsule.  In mallee open forest C. tepperi had recently commenced flowering.

In areas dominated by granite outcrops were found Eriochilus cucullatus flowering and perhaps another un-described Eriochilus species.  Leaves were not present, so no distinction could be made from flowers alone.  However, in mallee the flowers were larger and supported on much taller stems.  Those on the granite were small flowered on short stem, there being no apparent difference in the flowers themselves.  Here also the C. aff. rufa was seen in flower and capsule.

In the lower SE a sojourn into Honans Native Forest Reserve produced yet different species, some in flower.  C. ciliata was already in capsule, the distinctive greenish-yellow lateral sepals still evident and under magnification hairs could be detected on the labellum.  C. despectans had the very last flowers on the top of the scape as well as capsules on earlier flowering specimens.  Speculantha obesa had just commenced flowering.  In most cases the inward facing, smallish flowers had only the bottom one open with buds on the stem above.  Rosettes were not yet present. We were amazed to find Pterostylis nutans rosettes already emerging.  A little less surprising was Leporella fimbriata, but the number of flowers seen at this early stage was few.

The Marshes is not renowned for being prolific in Autumn flowering orchids but our visit was scheduled to try to locate as many as we could.  By the second day we were rewarded with the discovery of plenty of Spiranthes alticola, which were represented in most of the swamps in the western sector.  It is interesting to note that years ago they were found prolifically in the eastern sector but this appears to have dried out too much for them these days.  S. obesa was found in very low numbers and this time one of the plants already had a capsule.

Perhaps the greatest excitement was afforded when two members thought they found Cryptostylis subulata leaves.  All the surveyors collected for lunch and soon were down at the site considering if the leaves lived up to the name.  Much discussion ensued.  If only there was a flower to confirm the diagnosis.  After what seemed like an age a “tired” flower was located!  C. despectans had previously been recorded for the forest and a considerable amount of time was spent in searching known locations but to no avail.  Not Autumn flowering but the other orchid found was Dipodium roseum which was heavy with capsule.  Some of the stems had up to eight large pods hanging on them.

At Mt. Lyon Native Forest Reserve we were able to view many Cryptostylis subulata in flower and capsule.  Another trip was made to Honans to locate C. subulata from provided GPS readings.  After a bit of interesting navigation both swamps were located.  However we were unable to find the target species, one swamp appearing to now be too dry to sustain this species.

A quick trip was made to Telford Scrub Conservation Park following one of the survey days.  Here we saw Eriochilus sp. in flower.  This time they were large flowers with tall, almost robust stems.  Leaves were yet to emerge.  Another surprise was to await us here.  Bunochilus spikes were well up and it was evident there were two species represented.  Some of the spikes were quite pinkish with leaves still tightly furled on the spike.  Flowering will clarify more for us; some of the spikes will have a long growing time.

Upon completion of the surveys some members headed for Piccaninnie Ponds Conservation Park in yet another attempt to locate Eriochilus in flower.  This time we were successful.  It is a long way to travel when not knowing the exact flowering time for the area, and those times can change with each season!  On short thin stems, small flowers with still the same general appearance were what greeted us.  There were buds and capsules present as well, but most interesting to us was the presence of obviously earlier capsules.  One had already dehisced and all were far more robust and distinctly different from the smaller red-striped hairy capsules of the currently flowering species.

On next to more Native Forest Reserves.  Once again the target species was Eriochilus but we were hoping to find among the flowers some colourful pink specimens.  It seemed this time we were a little too early because few flowers were seen.  However, a strong coloured pink flower was located and so became much photographed.  The next area was low open forest with bracken and heath understorey.  Showers caught up with us and lowered the visibility very considerably.  This made it hard to look for small greenhood type flowers but possible to find, once again Eriochilus sp.  Some lovely double headed flowers were seen but no leaves were evident.

At this early stage of the year it was amazing how many orchids were seen, albeit over quite a wide ranging area.  Perhaps some worthwhile early rains in the lower SE had been useful, but most of the species are not heavily dependent upon this for their Autumn appearance.

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