Pterostylis gibbosa (R.Br.) Illawarra Greenhood Orchid Recovery Plan
NSW National Parks and Wildlife Service, September 2002
ISBN 0 731 36905 X
7 Previous management actions
- 7. 1 Conservation and Research Statement and Species Recovery Plan (ANCA Plan)
- 7. 2 Implementation of ANCA Plan
- 7.3 Southern Regional Forest Agreement
- 7.4 Recent Research
In 1994, a Conservation Research Statement and Species Recovery Plan was prepared for ANCA (now Environment Australia) (Quality Environmental Management 1994). The objectives of the plan were:
- to achieve more secure protection and management of the known occurrences of Pterostylis gibbosa;
- to further research the population dynamics of Pterostylis gibbosa in particular factors influencing variations in distribution, abundance and fecundity;
- to establish ex-situ cultivation of the Illawarra populations of Pterostylis gibbosa, if required;
- to further research the taxonomy of Pterostylis gibbosa, including confirmation of the possible Hunter Valley population, and the genetic variation between and within known populations of the orchid;
- to determine the full extent of the current distribution of Pterostylis gibbosa; and
- to protect and manage new sites if they are found.
Between 1994 and 1999, the following actions in the 1994 ANCA plan were funded by the NPWS and the Endangered Species Program (Environment Australia):
- to secure protection and management of known populations by liaison with relevant land owners;
- to survey areas likely to support P. gibbosa on the Cumberland Plain and the Illawarra and Shoalhaven Coastal Plain;
- to undertake research into population dynamics of P. gibbosa including:
- set up permanent quadrats to monitor survivorship, flowering, capsule and seed production;
- conduct seed viability and germination trials; and
- investigate the response of P. gibbosa to fire.
- to undertake taxonomy and genetic variability of P. gibbosa, particularly the Hunter population; and
- to review the existing draft recovery plan.
To guide the implementation of the ANCA plan, a Recovery Team consisting of representatives from Transgrid, Shellharbour Council, Wollongong University, Illawarra ANOS, NPWS and a private landholder from Yallah was established by the NPWS in 1996.
The Recovery Team continues to play an important role during the preparation of this plan, and to supervise and monitor recovery actions. The Recovery Team provides a forum to liaise with land owners and managers to secure protection and management of known populations. Other landholders not able to attend Team meetings are contacted regularly.
Between 1996 and 1998, surveys in western Sydney were conducted by the NPWS and ANOS in Prospect Reservoir, defence land at Orchard Hills, Holsworthy and St Marys, Shanes Park, Kemps Creek, St Andrew's, Longneck Lagoon, and Nurrangingy Reserve. No P. gibbosa was found despite the presence of ideal habitat in areas such as Shane's Park and Longneck Lagoon.
Further surveys in the Yallah area were carried out by Graeme Bradburn, Gary Leonard, Dr. Roslyn Muston and Axel von Krusenstierna in 1994.
In 1996, the area around Brown's Creek near Nowra was searched in an attempt to locate the site where the 1969 collection was made. The general area around Brown's Creek had been subdivided. Many properties were being used to graze cattle or horses. No P. gibbosa was found. Areas to the east of Brown's Creek containing suitable habitat was also searched but no P. gibbosa was found.
Further searches by NPWS and ANOS were undertaken during the 1997 flowering season in potential habitat in forest about 1.5km south-east of the area in Browns Creek where the 1969 record is believed to have been come from. The surveys in 1997 resulted in the discovery of between 300-600 P. gibbosa individuals in Currambene State Forest (now Worrigee Nature Reserve).
A survey in the Currambene State Forest was undertaken in September 1998 to establish the extent over which P. gibbosa occurs in the area.
Searches were also undertaken in the Hunter Valley in the vicinity of the Milbrodale population. In 1996, the Milbrodale population was confirmed as Pterostylis gibbosa and a survey was conducted to determine the extent of the population.
Since 1990, Graeme Bradburn and Rob Tunstall (Illawarra ANOS) have undertaken an annual census of the Yallah population using the quadrats selected by Whelan and Kohler (1991). Surveys were also carried out in surrounding areas (Area 3, 4, and 5). Data annually collected includes plant numbers and types, seedling numbers, flowering data and capsule count.
A census was carried out by Graham Kohler and Graeme Bradburn at Yallah and Albion Park to determine the size of the populations and distinguish between seedlings, mature plants and mature plants with flowering stems.
In 1997, 1998 and 1999 the NPWS and the University of Wollongong tagged and monitored individual plants at Currambene State Forest (now Worrigee Nature Reserve) and Milbrodale. The orchid parameters measured were:
- number of leaves;
- rosette diameter;
- height of scape;
- number of flowers;
- number of capsule;.
- number of buds and forming leaves;
- number of withered flowers;
- mature plants without scapes;
- damage to scapes; and
- plants missing.
Comments on damage to any parts of the plants, the state of plants and location of individuals in relation to other tagged plants were also noted.
Not all these parameters were included in every year.
In 1999, plants were tagged and monitoring work was undertaken at Albion Park.
The NPWS, in conjunction with the University of Wollongong, TransGrid and Illawarra ANOS, has undertaken research into the population dynamics of P. gibbosa including the monitoring of seed production, survivorship, and flowering capsule, seed viability and germination to enable informed management of the site.
In summary, the studies undertaken on Pterostylis gibbosa during the implementation of the ANCA plan are:
1996: Zoran Dokonal, as part of his Honours Environmental Science project at Wollongong University, undertook a study which aimed to survey orchid density in relation to site conditions at Yallah and Albion Park and to investigate the effects of grass removal through clipping at Yallah.
The study found that the environmental factors controlling the abundance and distribution of P. gibbosa at Yallah and Albion Park were light, moisture and space availability. No significant difference was found in rosette size, number of leaves, stem height or number of flowers per stem between the clipped and unclipped areas after one growing season.
1997: Elisa Heylin as part of her Honours study at the University of Wollongong investigated the effects of grass removal at Yallah (which followed on from Dokonal's study) and the effects of fire through post-fire observations at Albion Park. The study found a significantly lower average rosette size in clipped areas compared to unclipped areas. This was possibly due to a reduction in soil moisture levels in the areas where grass was removed. Grass clipping was found to have no impact on recruitment levels in the second growth season.
In comparing the effects of an accidental spring burn, an autumn burn and an unburnt area, Heylin (1997) found that the spring burn resulted in a lower average rosette size when compared to an unburnt area but had no impact on flowering of recruitment rates. The autumn burn was found to have no effect on orchid size, flowering or recruitment rates. It should be noted that this fire experiment was unreplicated and involved one spring burn and one summer burn at one location. The period of the study covered one post fire growth season.
1997: Some seed capsules were collected by NPWS for viability and germination trials. At Nowra, Milbrodale, Yallah and Albion Park, material was collected for genetic variability analyses at the Centre for Plant Biodiversity Research, Canberra.
1998: Inger Taylor undertook a research study on P. gibbosa as part of her Honours Environmental Science project at Wollongong University. The study aimed to quantify the level of herbivory on flowering stems and quantify the pollination rate of each of the four populations at Yallah, Albion Park, Nowra and Milbrodale.
The largest proportion of flowering stem damage was recorded at Nowra (41%) followed by Milbrodale (35%), Albion Park (27%) and Yallah (20%). The pollination rate of flowers (i.e. the proportion of flowers that form capsules) was found to be highest at Milbrodale (42%), followed by Nowra (39%), Yallah (9%) and Albion Park (7%).
Research is also being undertaken by the NPWS and Wollongong University to investigate the response of P. gibbosa to fire. An experimental burn was originally planned at the Yallah population for the 1997/98 season and then the 1998/99 season to test the responses of P. gibbosa to fire. Burns were postponed on both occasions due to unfavourable conditions. An ecological burn was undertaken at Yallah in December 1999 during the species' dormant season.
The final determination of the Southern Regional Forest Agreement (SRFA) on 1 January 2001 resulted in the gazettal of Worrigee Nature Reserve to protect the P. gibbosa population in the northern section of Currambene State Forest.
A Threatened Species Licence (TSL) was issued to State Forests of NSW (SFNSW) through the Integrated Forestry Operations Approvals process established by the Southern RFA. Under the TSL, SFNSW must meet the following conditions that relate to P. gibbosa before harvesting can occur in potential P. gibbosa habitat:
Where there is a record of the species within a compartment or within 20 metres outside the boundary of the compartment, the following must apply:
- A 10 metre radius exclusion zone must be implemented around all individuals; and
- An additional 10 metre width buffer zone must be implemented around all exclusion zones established under Condition 6.16.2a above. Limited operations (snigging and selective tree removal) may be conducted within the buffer. Hazard reduction burning must be excluded from the buffer zone to the greatest extent practicable.
- Where SFNSW can demonstrate to the satisfaction of the NPWS that the application of Conditions 6.16.1 or 6.16.2 for a particular species will significantly reduce the net harvest area then SFNSW may develop a Species Specific Management Plan as an alternative management approach.
- A Species Specific Management Plan must be developed in consultation with the NPWS and relevant independent experts and must consider:
- The species distribution and range;
- The conservation status of the species and extent of formal reservation;
- Any relevant Recovery Plan or Threat Abatement Plan;
- Alternative measures for amelioration of impact.
- Species Specific Management Plans must be approved in writing by the NPWS.
- Where SFNSW can demonstrate to the satisfaction of the NPWS that due to exceptional circumstances impacts on a flora species listed below or their exclusion /buffer zones (as required by Conditions 6.16.1 and 6.16.2) within a compartment are unavoidable, SFNSW may develop a Site Specific Management Plan as an alternative management approach.
- A Site Specific Management Plan must be developed in consultation with the NPWS and relevant independent experts and must consider:
- The population size both at the site and across the species range;
- The conservation status of the species and extent of formal reservation;
- Any relevant Recovery Plans or Threat Abatement Plans;
- The distributional significance of the site;
- The viability of the population at the site;
- The extent of proposed impact;
- Alternative measures for amelioration of impact.
- Site Specific Management Plans must be approved in writing by the NPWS.
- A Compartment Traverse must be conducted to search for threatened and protected flora species and certain threatened and protected fauna features;
- Samples of flora species that are unfamiliar to the surveyor must be collected and identified or verified by a relevant herbarium;
- The threatened and protected flora component and threatened and protected fauna features component can both be conducted at the same time, the minimum survey effort required is ten hours per 200 hectares of net survey area.
- For the threatened and protected flora component of the Compartment Traverse, the surveyor(s) must search in a random meander along the traverse identified in part 8.7.1 above, searching for and recording those threatened and protected flora species that require species specific or site specific conditions. The search should be conducted within the net survey area and in areas 50 metres outside the net survey area.
- A minimum of six person hours per 200 hectares of net survey area must be conducted along the traverse. Threatened and protected flora species requiring species-specific conditions must be searched for continuously along the traverse.
- If habitats not previously identified in the desktop component are encountered while sampling along the traverse, a proportion of the sampling time should be used to survey these habitats.
- The timing of the threatened and protected flora component of the compartment traverse should take into account flowering periods of the threatened flora species being surveyed (this is particularly relevant to orchids and annual species). Data on the known flowering periods of cryptic species is included in Schedule 2 of this licence where this information is available.
- Where individuals or groups of threatened or protected plants requiring these conditions are found, the individual or the extent of the group of individuals must be flagged (e.g. with flagging tape) by the person conducting the flora survey. The location of the individual or group of individuals must also be marked on the Harvesting Plan map to assist the Supervising Forest Officer in finding the flagged plant(s) during the compartment mark up.
Studies undertaken on P. gibbosa since the completion of the ANCA plan are summarised below:
Sharma et al (2000) investigated the levels of genetic variability and seed viability in all known populations of P. gibbosa. The study found a high degree of genetic variability and low population divergence between the populations. This was thought to have resulted either from recent population fragmentation or from extensive gene flow through seed and pollen movement. The study also found a high mean rate of seed viability (76%) existed for P. gibbosa populations.
Visman (2000) used a replicated fire experiment to determine the response of P. gibbosa to a summer fire in two areas of the TransGrid site. The study concluded that while there was an overall decline in population numbers at the site that year, the decline was less pronounced in the burnt quadrats than in the unburnt quadrats. This study also found that the effect of the summer fire on P. gibbosa flowering rates varied between two study areas, causing a decrease in flowering rates in one of the areas but not the other.