The Native Orchid Society is involved in many different activities, one of them being to assist researchers. In 2020, Covid 19 struck bringing many university projects to a halt. But in South Australia, NOSSA members were able to help PhD candidate Alex Thomsen, University of New South Wales, set up her project titled Impacts of Changing Fire Seasons on Orchids. The following video is her brief presentation of her planned research that she gave to the general membership at the September meeting.
Over the years, we have published several blogs concerning orchids and fire. At the beginning of the year, Renate Faast spoke at the NOSSA February meeting. John Eaton wrote an extensive summary of her talk which is reprodued here as it appeared in the 2019 March edition of the Native Orchid Society of South Australia Journal, Volume 43 Number 2.
Renate’s take home message was that we cannot make sweeping statement about orchids and fire, each species responds differently and we need to take this into account when planning proscribed. This was something that Dr Michael Duncan also brought out in his 2009 report following the Victorian Black Saturday fires – see Orchids and Fire.
An interesting aside to Renate’s research was her observations of white-winged choughs – see the paragraph Not All Relationships are Friendly.
Guest Speaker Notes John Eaton
At our February 26th meeting, thirty NOSSA members were treated to a stimulating talk by Dr Renate Faast from the University of Adelaide – our first guest speaker for 2019.
Renate acknowledged the support her project received from an Australian Research Council (ARC) grant under the Linkage Program which promotes national and international research partnerships between researchers and publicly funded research agencies – in Renate’s case – support from the University of Adelaide, SA Museum, SA Water, Forestry SA, The Australian Orchid Foundation, the Nature Foundation of SA, The Environment Institute and the SA Government.
Renate had been getting mixed messages from the field observations people had made following prescribed burning or bushfires. This ARC grant enabled her to study the impacts of prescribed burning on native terrestrial orchids.
Renate found that the response of orchids to controlled burns suggests that there are winners and losers amongst orchids: Naked sun orchids responded really well to a controlled burn with 6 plants growing to 83 plants. REALLY good news for that species of orchid but the reality is more complicated than that and this study suggests that there are no generalisations that can be drawn with any confidence about regeneration following prescribed burns or bushfires! In view of the complex interactions between orchids and other plants, and between orchids and bird-and-animal grazers, orchids rely on so many things to go right in order to set seed and recruit new plants into a population. With the exception of a few self-pollinating species, most orchids rely on pollinators for seed production. For non-clonal species, releasing seed is the only way to ensure the species’ long-term survival!
Not all relationships are friendly
Over 80% of orchid flowers had been grazed at some sites. No flowers means no seeds. Renate’s film clips embedded in her PowerPoint dramatically showed the extent of orchid predation by birds such as white-winged choughs and currawongs. They picked off the flowers quite deliberately, leaving behind an intact stalk. Five flowers were grazed every 10 sec (that’s at a rate of 30 flowers/min!) And there are all the other orchid grazers such as roos, deer and rabbits as they move through a patch, often only grazing part of the stem, in a far less targeted and thorough way, compared to these birds. All of these interactions play a key role in whether seeds are released to keep the population viable.
The Mount Bold Fire prompt
While engaged in her PhD research into reproductive ecology of spider orchids, Renate heard that a fire at Mt Bold had led to a “profusion” of Caladenia rigida flowers! The Victorian bushfires had also prompted changes to prescribed burning practises in South Australia. The combination of these two events led Renate to explore the effect of fire on the interactions orchids have with other plants and animals – leading her to ask such questions as:
Does fire promote the flowering of spider orchids (e.g. Caladenia rigida, C. behrii, C. tentaculata) and Glossodia major?
If there are more flowers following fire, will they be pollinated and will they set seed?
How does burn timing influence this response?
Do all species respond in the same way?
These are all critical issues to consider if we are to ensure a self-sustaining orchid population in the future.
There are seasonal influences on the effects of a burn. The response to a summer bushfire could be quite different from cooler season burns in autumn and spring. And even if some orchids are stimulated to flower, it doesn’t necessarily mean that they will end up producing and releasing more seed – which is what really matters for the long-term survival of the orchid population.
Orchid monitoring was carried out in several sites and included 1 autumn, 3 spring burns and 4 adjacent unburnt control sites across the Mt Lofty Ranges (NE of Adelaide). Renate followed the fate of 4 species by tagging up to 150 plants for each species. Renate’s presentation focused on the Millbrook sites where she studied C. rigida and G. major before and after a prescribed burn conducted in Autumn 2013. Unfortunately and fortuitously, her control site also became a bushfire site following the Sampson Flat Fire in January 2015. Fortunately, the Autumn burn site was not affected by the Sampson Flat Fire, so became something of a control site! Renate found that 97% of C. rigida did not emerge after the Autumn prescribed burn compared with 8% at the unburnt control affected site. Flowering was not promoted and no tagged plants flowered. A similar but less severe effect was recorded for Glossodia major.
Will these orchids recover in subsequent years?
Annual monitoring up until 2017, revealed that over one third of C. rigida plants did not re-emerge for 5 consecutive years after the autumn burn. Unfortunately, these plants are likely to have been killed by this burn, probably because the fire was conducted as the orchids were about to emerge. Interestingly, spring burns did not have a detrimental impact on the orchids studied, however, a proportion (18 – 28%) of C. rigida plants may also have been killed by the summer bushfires.
One of the more striking findings out of this research was the large increase in pollination for C. rigida following the bushfires – up to 65% of flowers (protected from grazing) produced a seed pod – an unprecedented rate for Renate’s research. It seems that in the sparse blackened landscape with very few other plants in flower, C. rigida had most of the attention for pollinators. However, the removal of understorey cover also meant that grazing rates were higher after the fires, and most of the flowers that were not protected inside cages were eaten. This meant that there was no actual benefit to the orchids, as there was no increase in seed release. All of these responses were short-lived, and by spring 2016, pollination, grazing and seed release rates were much the same as before the fires.
All species are not equal – fires may benefit some species others don’t fare so well; All fires are not equal; Autumn burning may be detrimental to SOME species; Bushfire may benefit seed release, only if grazing pressure is low – and Flowering was not promoted by any fire. More research is needed on other species, and in different habitats.
Therefore, Renate pointed out that no generalisations can be made about her observations!
Some good news that has come out of this research:
Burn practices are changing, with land managers taking into account the timing of prescribed burns, and bestattempts are made to avoid late autumn burns in areas containing threatened (early-emerging) orchids;
Impacts of fire on reproductive success appear to be short-term
Renate’s hope is that one day, the message will get out there that while some orchids can respond well to burning, this isn’t the case for all species – and that we still have a long way to go before we will really understand the complexities that underlie these different responses with any degree of predictability. Renate also warned that over a third of SA’s orchids are threatened with habitat loss, weed invasion, pollinator loss, grazing and fire regimes.
Renate’s address was followed by a flurry of burning questions and observations. It is hoped that we NOSSA members will use Renate’s conclusions to guide and inform our own anecdotal field observations and test our underlying assumptions and prejudices about the effects of burning on orchid viability – especially as we enter an unprecedented and potentially species-destroying period of human – induced global warming.
Continuing last week’s blog, here is the completion of Rudie Kuiter’s Introducion, Orchid Pollinators of Victoria. In this section he discusses some factors of hybridisation and the value of regular observation by local people interested in orchids.
Lissopimpla excelsa is the pollinator of all members of Cryptostylis, but hybrids are not known, even when sympatric, thus a molecular mechanism is in place that prevents cross-fertilisation. Hybrids in other orchid genera do occur and these usually are amongst closely related species. Several congeneric orchids attract the same male pollinator species, thus would be emitting the same kairomones, the scent that is a mimic of the female’s sex-pheromones, but normally these orchids are allopatric or have different habitat preferences. The land clearing, frequent fires, changes of watercourses, gold-diggings are amongst many unnatural human habitat interference of recent times. Historically in undisturbed natural habitats sibling orchid species that attracted the same male insect were not sympatric, not flowering at the same time or were in close vicinity to each other. In disturbed sites the situation has changed, as closely related species may have become sympatric and hybridisation take place. Spider-orchids that attract thyniid wasps with kairomones normally target a certain local species, but many allopatric species are know to share the same pollinator and readily hybridise where they became sympatric. In Pterostylis greenhoods the known hybrids are also caused when different species attract the same pollinators.
We still have much to learn to fully understand how adaptable the orchids are, the role insects play and how to interpret what we see. Orchids are finely tuned to their world and can change and adapt in ways that most people seem to underestimate. I requires observations of the same plants over many seasons to get a good understanding of their variability and adaptability. Unusual forms often show after a drought or fire may look like a new species, but soon change back to typical or normal within a few good seasons or after regeneration. It is usually the local people taking an interest that see the changes in the same plants over time that dispute what the ‘on-the-fly’ taxonomist come up with.
Creatures evolved as part of an endless combination of life-forms, ranging from microscopic to the tallest tree, that together form an ecosystem in which all organisms depend on each other. The climate, weather and other factors changes the environment constantly that influence the members differently, dome doing better than others, but it collectively maintains a balance. Natural events such as a major fire or flood may benefit environments in areas as part of seemingly long cycles, but they are very short in evolutionary terms. Unnatural man-made fires are very destructive as these are conducted much too frequently, wrong time of the year, and in the wrong place. Not obvious, but also very detrimental is the use of insecticides that seems to effect the Diptera members the most. Many of the important pollinators such as the fungus-gnats have gone locally extinct and most of the Pterostylis depend on them. To work with the pollinators it is essential to have a good understand of the life-cycles of the insects involved and watch the flowers in the wild. After witnessing Pollinator behaviours of the fungus-gnat on Pterostylis nutans countless times, the principal pollinator is easily recognised with other species. Unfortunately few good areas to find orchids and learn about their pollinators are left. Many are now rare and measures taken to protect them usually focuses on just a species. To be effective their habitat area and surrounding needs to be cared for, letting the natives grow and have the natural canopy reform. At least, habitats should be protected from further disturbances, especially by badly informed governmental environment departments with their fires.
Note This book is solely based on first-hand observations on the orchid-pollinators in the wild. Descriptions and comments are from many hours of watching each species over multiple seasons.
Apart from Orchid Pollinators of Victoria, Rudie Kuiter has produced several Victorian orchid books. If you are interested in purchasing any please contact us.
This week’s blog, Part One of Two Parts, is quoted directly from the introductory chapter (Pages 2&3) Orchid Pollinators of Victoria 4th Edition, 2016, Rudie Kuiter. Over the years of photographing orchids and their pollinators, Rudie and his team have been discovering much of the hidden world of orchid pollinators. In this first section he highlights the fallacy of the “one orchid-one pollinator” as well as touching briefly on the vast difference between the insects and their role in the ecosystem.
Amongst flowering plants, orchids have evolved in their own special reproductive ways. Their pollen is massed as waxy packages, pollinia, unlike like (sic) other flowers that produce masses of fine pollen grains that mostly go astray. The pollinia are relatively heavy and the usually small creatures need to be strong fliers for cross pollination (see image below). Orchids evolved with amazing strategies to attract specific carriers in order to transfer pollen between flowers of their species only, and in this way eliminating the need to produce great quantities. Various insects, many moths, bees and even birds have been documented as pollinators of orchids around the world (v.d. Cingel, 2001). A number of uniquely different examples of orchids attracting insects for their pollination evolved in Australia, especially in the more temperate southern zones originating from Gondwana times. With very few exceptions the Victorian orchids are terrestrial, ground-dwellers, that rely on small insects such as fungus-gnats, native bees, wasps, ants and many attract only the males by sexual deception. In the case no pollinators visits, many species may self-pollinate as a back up.
When taking an interest in orchids it seems difficult enough to identify some species. Usually one looks and admires the amazing flowers that may resemble an insect and can be difficult to recognise as a flower at first. An insect on a flower may be thought of something that spoils a picture – until taking an interest in the visitor!
I first learned about the orchid pollinators in Orchids of South Australia by Bates & Weber, 1990, an excellent book by today’s standard, but few were seen over the years by just being there at the right time when photographing orchids. During preparation of the book on Caladenia spider-orchids, certain issues developed from questionable statements made in scientific papers about wasp-pollinators. Of particular concern was about the one-to-one relationship – how only one wasp-species would be involved with only one spider-orchid species – and suggesting populations that were thought to represent the same species comprised different taxa if not pollinated by the same wasp-species. A very different story emerged when monitoring the local spider-orchid populations to find the answers and it became clear that there was much more to it. A site in Wonthaggi with a very large colony of Caladenia dilatata proved to be perfect for this study and also to photograph pollinators as it produces flowers for about four months. It was found that a local wasp-pollinator species typically flies for a little over one month, thus this need to be investigated further. Scientific publications on wasp-pollinators were generally based on short-term experiments, and usually employing baiting methods – moving flowers and often taking them to different sites. Responses included unnatural behaviour or attracting sibling wasps at a non-local site. It is certainly true that a particular flower may attract only one species of wasp a t a locality and a certain time in the season, but this reflects a very small part of the picture. It can be different in the long-term, at certain localities or with a season.
The main study site was in coastal dunes, where in a very large population of Caladenia dilatata produced flowers for over four months from September, and under favourable Summer-conditions into January. At least three congeneric (belonging to the same genus) thynniid wasps species were involved in this population. The flying times were up to about 6 weeks for each wasp species, that were separated or slightly overlapping. The flowering times in other populations of C. dilatata in Wonthaggi and Wilsons Promontory were usually about one month in each, and at the corresponding times to the study site the wasps visiting were the same species. A close sibling C. parva in the Wonthaggi heathland habitats and early flowering C. dilatata were pollinated by the same species, but the later flowering C. tentaculata by a thynniid wasp of the different genus.
Whilst a flower may attract only one wasp species, the kairomones (chemical omitted by the orchid to attract a pollinator) of a species may vary between flowers within in a population or when allopatric (growing in different geographical regions), just like colour or morphology. Variations maybe in relation to locality, weather conditions, or ground chemistry and available pollinator. Pollinators may evolve over time, but adaptions usually require many seasons and this would vary with location. The observations made over several seasons suggest that more than one congeneric insect is involved in pollination depending on local or seasonal conditions, especially after a long drought. Chiloglottis gunnii populations in Langwarrin were checked for pollinators since a decade-long drought and no action was seen for many seasons. When wasps finally made an appearance they comprised different taxa of Neozeleboria the first season, but only one became the common and principal pollinator the following seasons. Thynniid wasps are very localised as females lack wings and rely on the males to carry them around during copulation and to provide food. It limits their travelling and their homing range may comprise just a few hundred metres. Thynniid wasp are very vulnerable in small reserves isolated by land-clearing, and certain species have gone locally extinct due to conducting burns. Insects form a crucial and fundamental part of an ecosystem, but their importance is never considered in the planned burning, showing a complete lack of understanding by people in charge. So little is known of ecosystem’s foundations, but controlled burning continues – ruining precious habitats. Orchid species failing to produce seed pods is an indication that pollinators were absent, probably gone locally extinct. Orchid species that have a sexual association with thynniid wasp pollinators are localised and usually have geographically variable flowers. The situation is different with Cryptostylis spp. And their pollinating male wasp Lissopimpla excelsa, as females are a strong flyers. The flowers of Cryptostylis are geographically uniform in each species and the wasp is widespread. Both sexes are very distinctive in colour that show no variation. They are active over Spring and Summer and are great travellers.
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.
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, Acianthuspusillus, Corysanthes (Corybas) species and Cyrtostylisrobusta 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 Thelymitramatthewsii 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, Glossodiamajor, 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. Glossodiamajor was encountered as mainly single plants widely scattered. Caladeniacarnea 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 Prasophyllumelatum. 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.