Conservation Research Statement and Species Recovery Plan for (Persoonia nutans) R. Br. 1996

Geoff Robertson, Maria Matthes, Martin Smith
NSW National Parks and Wildlife Service
Environment Australia

1. Conservation research statement- Persoonia nutans

1.1 Introduction

Persoonia nutans R. Br. (Proteaceae) is an endangered plant species, known only to occur in the Cumberland Plain, Western Sydney (Figure 1). Western Sydney has undergone rapid urban expansion in the last decade. Penrith Local Government Area - the stronghold of P. nutans - has one of the greatest population growth rates in Sydney and a large demand for residential land (Mathias & Carter, 1991).

Figure 1: The original distribution of Persoonia nutans

Original Distribution Map

1.2. Study Environment

The Cumberland Plain is generally flat to undulating in a low lying basin (20-100 m a.s.l.), bounded by dissected sandstone plateaux to the north, south and west (Doherty, 1987; Figure 2. from Benson, 1992).

Figure 2: The Cumberland Plain

Topographic Map

1.2.1 Land-Use History

The Cumberland Plain is the oldest settled district in Australia (Corbett, 1987). In the 1790's early settlers cleared the floodplain forests of the Hawkesbury River for intensive agriculture and used the Cumberland Plain Woodland for grazing and timber production (Benson, 1991). In 1810, Governor Macquarie established farm lots around Castlereagh, Windsor and Richmond (Proudfoot, 1987) and in 1820 established Campbelltown.

By 1984, 79.8% of north-western Sydney had been cleared and several significant areas since then (Antcliffe, 1988). Approximately 1% of Western Sydney is reserved for conservation (Benson, 1991; Cohn & Hastings, 1994).

Castlereagh Nature Reserve was managed by State Forests of NSW until 1996. It was gazetted State Forest in 1917 at twice its present size. The excised portion was revoked for Castlereagh Liquid Waste Depot and a jail (Doherty, 1987).

The vegetation in the Agnes Banks area has more recently been cleared extensively for sand, clay and gravel extraction (Doherty, 1987; Benson, 1991; 1992). About half the original sand area had been cleared or quarried by 1972 and most of the remainder committed for future sand extraction (Benson, 1981).

The Southern part of the Cumberland Plain was recognised for its farming potential by 1793 when cattle that had escaped from Sydney were found near Camden. Only isolated fragments of the original woodland remain, as farming in the 19th Century, and housing and industrial development in the 20th Century have taken their toll (Benson & Howell, 1990).

1.2.2 Geology & Soils

Persoonia nutans is found on the Agnes Banks and Berkshire Park soil landscapes. The largest population (approx. 2,500 individuals) occurs on the Pleistocene aeolian sands at Agnes Banks. These have high permeability, low to very low fertility and low available water capacity. The Agnes Banks sands conformably overlie the Berkshire Park (bp) soil landscape.

The bp formation is a Tertiary alluvial sediment derived from sandstone and clay, and consists of sandy loams, sandy clays, clay loams and heavy clays. Stones and ironstone nodules are common, indicative of lateritic soils. Soils are of low permeability, low fertility, low available water capacity, are strong to very strongly acid and in places have high aluminium toxicity (Bannerman and Hazelton, 1990).

1.2.3 Climate

The average rainfall for the Cumberland Plain is lower than other areas of Sydney, with an annual average of 700-1000 mm (Doherty,1987). At the University of Western Sydney at Richmond, the closest station to the largest P. nutans populations, data has been recorded since 1881. January is the hottest month with an average maximum temperature of 29.4° C, while July is the coolest month with an average maximum temperature of 17.3° C. The average minimum in July is 3.2° C. Median annual rainfall is 803.6 mm with less rain in winter than in summer (Bureau of Meteorology), Figure 2.

Figure 2: Median monthly rainfall at UWS, Richmond.

Monthly Rainfall Graph

1.3 Description of P. nutans

P. nutans is an erect to spreading shrub to 2-2.5 metres high with yellow flowers and reddish stems and branches. The following description is from Weston & Johnson (1991a, 1991b):

The leaves are alternate, linear-oblong, acuminate, 1-4.5 cm long, 1-1.8 mm wide. They are usually flat with recurved margins, sometimes recurved toward the tip and slightly falcate, and are strongly discolorous. Sparse, short, mostly appressed hairs are present on the leaves when immature and are smooth and glabrescent when mature. Inflorescences axillary or terminal, usually growing on into a leafy shoot, with 1-40 flowers on a rachis 0-25 cm long. The flowers are mostly subtended by leaves; pedicels 7-12 mm long, recurved, glabrous. Tepals 8.5-11 mm long, shortly caudate, glabrous. Ovary glabrous with 2 ovules. The drupes (fruit) are green with purple markings.

Persoonia nutans buds and flowers

Persoonia nutans buds and flowers

1.4 Conservation Status

P. nutans has a risk code of 2ECi (Briggs & Leigh, 1996) which indicates it has a distribution less than 100 km, is in danger of becoming extinct in the wild within 10-20 years, and although found in a conservation reserve is not adequately conserved. It is also listed as E on the ANZECC (1993) list, and is on Schedule 1 of the NSW Threatened Species Act, 1995, as an Endangered species.

Continued habitat loss via urban development, particularly in the south of the Cumberland Plain, could result in the extinction of several populations.

1.5. Distribution and abundance

The distribution of P. nutans is restricted to the Cumberland Plain between Richmond, Macquarie Fields and East Hills, particularly near the Nepean and Georges Rivers (Weston & Johnson, 1991b). P. nutans was probably never widespread on the Cumberland Plain as is confined to aeolian and alluvial sediments. Near Richmond and Windsor these deposits are extensive and presumably are the reason for the greater abundance of the species in the Northern end of the plain. In the South these deposits are limited, primarily to the vicinity of the Georges River near Liverpool.

P. nutans was first collected in 1801 by Robert Brown near Richmond, at the confluence of the Nepean and Grose Rivers. Herbarium records show that P. nutans has been found at 19 different locations, although the exact number is somewhat sketchy due to imprecise locality information.

Half of the recorded locations of the species, including Robert Brown's type collection in 1801, have been cleared. The low fertility of the soil and location on the outskirts of Sydney has probably helped preserve the remaining populations. Populations recorded in St Marys, Macquarie Fields, Glenfield, Pleasure Point, Appin and Yarramundi have all disappeared.

This survey found 9 of these extant with the total population estimated at approx. 6300 individuals (Table 1, with full details in Appendixes 2 & 3). Sites that are less than 500 metres apart are regarded as being part of the same population. Hence the large number of sites, but only 9 different populations.

The total range of the species is 35 km E/W and 38 km N/S. The sites are clustered into two main areas: just south of Richmond, and another group near Liverpool.

Table 1: Population numbers at each location.

LOCALITY

NUMBER

AGNES BANKS

4327

CASTLEREAGH NATURE RESERVE

258

WINDSOR DOWNS NATURE RESERVE

65

LONDONDERRY

1496

BANKSTOWN

5

CAMPBELLTOWN

110

LIVERPOOL - KEMPS CREEK

3

LIVERPOOL - NEAR HEATHCOTE ROAD

11

LIVERPOOL - VOYAGER POINT

3

TOTAL

6278

It is difficult to place precise limits on the boundaries of the populations near Richmond. Provided the soil conditions were suitable P. nutans did not appear in discrete, easily counted populations. While there were populations that were aggregated, in other places such as Windsor Downs N.R., Castlereagh N.R. and the undisturbed parts of Londonderry individuals are scattered through the woodland. Surveying in these areas would undoubtedly reveal more individuals. With the likelihood of only finding isolated plants extra surveys were not feasible in this study.

P. nutans was found in 1993 in the Australian Defence Industry Site proposed for sub-division. This site was not examined because access was refused.

In the Liverpool area the populations are localised due to the limited extent of the bp soil landscape and because suburban development has isolated several of the populations.

The population occurring on the aeolian sands at Agnes Banks comprises 69% of the total number of individuals. So many plants occur at Agnes Banks that total numbers were estimated. About 4,300 plants occur there (details in Appendix 2). This population has probably been significantly reduced in size as a result of sand mining to the north and east. Air photos show that only a small proportion of the sands remains unmined. Approximately 1,380 of the remaining plants are growing in portions that will be mined in the future.

Only 2.1% (132) of total number occur on the Southern part of the Cumberland Plain in the Liverpool area. These are found in 5 sites, 4 of which have fewer than 12 individuals. More thorough surveys need to be conducted near Liverpool as there are several outcrops of suitable soil supporting a canopy of E. sclerophylla and A. bakeri, the dominant canopy species where P. nutans occurs. The largest occurs on Holsworthy Military Area. This expanse of the bp soil landscape is contiguous with the population at Voyager Point. An area of private land in between the populations of Voyager Point and Heathcote Road is worthy of investigation, plus the Holsworthy Base.

1.6 Habitat

P. nutans grows in Castlereagh Scribbly Gum Woodlands and in Agnes Banks Woodland (classified by Benson, 1992). In Castlereagh Woodlands it is found in open woodland with dominant overstorey species being Angophora bakeri, Eucalyptus sclerophylla and Melaleuca decora. Other species in the overstorey are E. parramattensis and Eucalyptus fibrosa. Common associated understorey species being Melaleuca nodosa, Hakea sericea, Dillwynia tenuifolia, Micromyrtus minutiflora, Banksia spinulosa, Acacia elongata, Themeda australis, Cyathochaeta diandra, Xanthorrhoea minor.

The Agnes Banks Woodlands have a similar array of tree species, with the addition of Banksia serrata and Banksia aemula. Eucalyptus fibrosa is absent from the sands. The understorey occurring on the sands is very different to that found on the adjacent Londonderry Clay, having affinities to coastal dune communities rather than Cumberland Plain associations. Soils are dissimilar, with permeability on the clay being much lower than the Agnes Banks sands. Benson (1981) distinguishes five communities along a drainage gradient at Agnes Banks.

Drainage appears to influence the distribution of P. nutans as the species is more common on the deeper sands at Agnes Banks than at the edge of the deposit next to the Londonderry Clay. At other locations on the Cumberland Plain it occurs on low rises as opposed to swales or other low lying areas.

A full description of surveyed sites is provided in Appendix 2.

1.7. Population Dynamics

The biology and ecology of P. nutans is not well understood. Current knowledge is based on general observations. No quantitative data has been collected. One problem with a single survey is that there is no appreciation of the fluctuations in numbers over time, or any knowledge of seasonal changes in flowering, fruiting etc.

Three kinds of population structure were evident:

  • High population density in undisturbed habitat at Agnes Banks on sand.
  • Low population density in undisturbed habitat on the clay.
  • Very high population density on disturbed land at Londonderry and Maquarie Fields.

Regenerating shrubland adjacent to the Drop Zone with a very high density of P. nutans

Regenerating Shrubland

The soils were lateritic where P. nutans was present in disturbed landscapes.

P. nutans growing on laterite at the site shown above

P.nutans growing on laterite

Only the occasional seedling or small plant was found in the undisturbed areas. More small plants were present in the disturbed habitats.

1.7.1. Regeneration and Recruitment

Persoonia nutans is an obligate seed regenerator. In the event of a fire all existing plants of P. nutans are killed. Obligate seeders regenerate after fire by seedlings, depending on pre-fire seed storage and dispersal (Keith & Bradstock, 1994). There are juveniles at some sites, showing that recent recruitment has occurred from seed. Further study at recently disturbed populations is required to examine seedling recruitment.

Four, and possibly five sites were discovered where P. nutans appears to have colonised land that has been completely cleared. If the Agnes Banks population is excluded, 4 of the 32 locations with P. nutans possessed 77% (1511) of the individuals found in the survey. The Agnes Banks population is excluded since it occurs on a different soil type to the rest of the populations. Whether the 'disturbed' populations regenerated from a seed bank left in the soil, or whether there was dispersal of seed from surrounding areas into the disturbed areas is not known.

In dense parts of the woodland at Agnes Banks, where the understorey was about four metres high, old senescent P. nutans were found. P. nutans frequently occurs beside the tracks at Agnes Banks. These plants appeared healthy, being covered with many flowers and fruit, in contrast to senescent plants often only metres away in the understorey. Some of the largest individuals were found on a disused track adjacent to thick bush containing senescent plants.

These observations, coupled with the ability to successfully colonise cleared land, indicates that to persist P. nutans requires disturbance (and is capable of surviving extreme disturbance). Fire has probably been the primary agent of disturbance in the past. Research is needed to determine the time taken for a population to replenish the seed bank after a fire, and how long it takes for plants in the community to become senescent.

Studies of other obligate seed regenerators by Auld et al (1993) found that seed production reached a peak at least 10 years after fire before declining. Survival of P. nutans in the long term will be best achieved by management for of the whole community, but prescribed burns may be needed. For P. nutans, Agnes Banks may be approaching the limit between disturbance events. At present the number of tracks providing open conditions is probably important in maintaining a viable population at Agnes Banks.

Small, senescent individuals were encountered, particularly in the populations colonising disturbed ground. It is not known whether this is just a seasonal phenomenon or whether there is high mortality in these areas.

Wallabies and birds such as Currawongs are known to disperse Persoonia seed after eating the fruit (Rose 1973, Buchanan, 1989, T. Auld, pers. comm.). It has been suggested that passing through the gut of these mammals may assist the seeds to germinate. Preliminary trials by T. Auld using seed recovered from scats of swamp wallabies found no change in dormancy or viability of some Persoonia spp.

Germination of P. virgata has been achieved by removing the endocarp (Ketelhohn & Johnston 1995). Provided the removal of the endocarp has not damaged the seed germination rates are high. In natural conditions the endocarp is believed to prevent germination until decomposition has progressed to the point where the seed may imbibe. There is no data on the length of this process, or the conditions required for this to occur (eg is a fire necessary?).

If seed germinates following decomposition of the endocarp a continued trickle of seedlings, or a pulse of germination from each years seed would be expected once populations had become established. This was not observed, although it is possible that seeds germinate but there is not significant establishment until after disturbance. Juvenile plants were very rare, indicating that additional controls over the timing of germination probably exist. In other Persoonia species there is dormancy that can be overcome using high concentrations of gibberellic acid (P. Weston, pers. comm.).

1.7.2. Phenology and Fecundity

The flowering period is from November to April (Weston & Johnson, 1991b) with a few flowers all year round (Bernhardt & Weston, 1996). Most populations have been observed with flowers and fruit during the survey period of May and June 1996.

Large numbers of fruit were found on most plants. Plants only 1m high often had in excess of 300 fruit. Some plants were found in Agnes Banks that were roughly hemispherical in shape, being 2.5 metres high and 3 metres in diameter. The number of fruit on these specimens was estimated to be in the thousands. Even plants only 30 cm high had borne fruit. Several were found that possessed up to 60 fruit.

1.7.3. Breeding System and Genetic Diversity

It is likely that the genetic variability within P. nutans has reduced since European settlement simply through the destruction of sites, particularly at the southern end of the species' distribution. The genetic diversity within and between populations of P. nutans is unknown. The breeding system of the species would influence the degree of difference between populations.

Outbreeding species tend to have much less of the overall diversity represented between populations than selfing species. Krauss (1994) found that self fertilisation in the Persoonia mollis complex rarely resulted in successful seed set. Field observation of P. nutans showed that plants apparently isolated by several hundred metres from the nearest neighbour still possessed large numbers of fruit. This may imply self fertilisation, but this would be unusual as most Persoonia species are believed to out-cross (P. Weston, pers. comm.).

Gene transfer could occur between the populations of the Northern Cumberland Plain, and between the populations around Liverpool via the dispersal of fruit by vertebrates. Provided the species outcrosses gene transfer could then occur over long distances. Pollen dispersal by native bees could also link some populations. Leioproctus and Chalicodoma native bees have been observed carrying P. nutans pollen (Bernhardt & Weston, 1996) and are likely to be the primary agents of cross-pollination. Other vectors may also be important.

It is not considered necessary for the management of the species to undertake an investigation of the genetic diversity. For small populations of a few plants, however, it may assist in their management.

It is important that the genetic diversity represented in the Liverpool populations be retained. The plants around Liverpool may have a different genetic composition from the populations on the northern Cumberland Plain. Although gene transfer over the 40 km is possible, it is unlikely, and hence the Liverpool populations are probably genetically distinct. Seed should be collected from the Liverpool populations that are at most risk of extinction.

1.8. Current Status of Populations

1.8.1. Land Tenure and Zoning

P. nutans occurs on land owned by the Crown and freehold (Appendix 3). Three populations, those at Windsor Downs Nature Reserve, Castlereagh Nature Reserve and at Agnes Banks Nature Reserve are officially conserved.

Unfortunately the densest populations at Londonderry and Agnes Banks are not protected by reservation. A Permanent Conservation Order was placed over part of the Agnes Banks area in 1989. Most of this area was subsequently incorporated into Agnes Banks Nature Reserve in 1995. Only an area 400 metres x 80 metres remains covered by the PCO. In total approximately 1967 of the total Agnes Banks population are protected.

Of the wooded land outside the PCO/Nature Reserve at Agnes Banks about 15 ha. is leased by P.B. White and has a development consent for mining, while another 10 ha. (Lot 43 and Lot B) is freehold land owned by CSR.

The P.B. White land will be mined in the future, leaving approx. 1000 plants in the block owned by CSR. A development consent for mining has been issued over the already cleared part of CSR's block. CSR have not been granted approval to mine the wooded portion of their land and will need approval from the relevant authorities to do so.

The populations near Liverpool are in a perilous situation. The small size of the populations renders them very susceptible to extinction. Only the population at Macquarie Fields in Simmos Beach Reserve has any protection at all. This is declared Regional Open Space. A freeway was proposed to pass through this reserve, which would affect the population if it were built. The freeway was intended to serve the new satellite city of Appin, the development of which has been postponed.

Other populations occur on Vacant Crown Land near Londonderry with Aboriginal Land Claims under the Land Rights Act, 1988. The future of these populations will be determined pending the assessment of the land claims and any subsequent development proposals.

1.9. Threats

Several threats are reducing the capacity of P. nutans populations to be self-sustaining. These threats include: inappropriate fire regimes, mining, vegetation clearance, unrestricted access, rubbish dumping, exploitation and weed invasion.

1.9.1 Inappropriate Fire Regimes

Fire has the potential to eliminate entire populations if they occur too frequently. Study of the fire ecology of P. nutans is needed before predictions can be made about the inter-fire periods and intensity of fire that are most appropriate. In the interim fire should be suppressed in those populations that have not yet produced fruit so that the seed bank may be replenished.

1.9.2 Mining

Mining leases and associated development consents affect the part of the population at Agnes Banks. The consents include areas containing the densest concentrations of P. nutans in undisturbed habitat. These areas, north of the Nature Reserve on deeper sands are more attractive economically. Fortunately P. nutans does occur throughout the entire sands area, but with lower numbers in the south. Only a small proportion of the vegetation community on deep sands is conserved in the Nature Reserve/PCO area.

1.9.3 Vegetation Clearance

Populations in the Liverpool area are likely to be affected by clearing for suburban development. The populations at highest risk occur on private property at Kemps Creek, the Taubmans Site and the population(s) near Heathcote Road.

Vegetation clearance is continuing on the Cumberland Plain. Sites near Londonderry that are known to have possessed P. nutans in the past have been cleared.

The Commonwealth leases several portions of land west of Londonderry. Two portions are used by the armed forces for parachuting practice, an area known locally as the Drop Zone. Periodically the army clear the D.Z. of vegetation. P. nutans occurs on the boundary of the zone and some plants recolonising the D.Z. are probably destroyed during each clearing operation. Further increase in the area cleared is unlikely.

1.9.4 Unrestricted Access

All of the unreserved populations are at risk from vehicular damage. At most the sites there is an extensive network of tracks through the landscape. The flat terrain, open woodland and often sparse understory make it easy for drivers to leave the existing tracks to avoid obstacles. New tracks have been created that often lead nowhere, or create a minor shortcut. At Londonderry tracks evident on aerial photos taken 10 years ago are no longer used, but new ones have been established. Several populations have been affected by this damage. Fencing, or permanent obstacles to prevent vehicles but not inhibit animal movement may be required around the most significant populations. Education to encourage an appreciation of the local natural environment is needed, however this is unlikely to have much effect in the short term.

Track bypassing a bund which was built to stop access to a trail

Track bypassing a bund which was built to stop access to a trail

1.9.5 Rubbish Dumping

The attitude and perception of bushland by some parts of the community are reflected in actions such as rubbish dumping (Perkins, 1991) - a physical problem in that large quantities of rubbish (household, building and industrial) can smother the populations of P. nutans. Other sites are also affected by the dumping of stolen cars. This may have an immediate impact on individuals, but more seriously the vehicle is often burnt, providing the additional threat of fire.

Dumped chairs next to P. nutans

Chairs dumped next to P.nutans

1.9.6 Exploitation

P. nutans is an attractive shrub, already grown for the nursery industry. If demand for this species increases and unmonitored collection of wild sources continues, there could be detrimental impacts on the wild populations.

1.9.7 Weed Invasion

The Castlereagh Scribbly Gum Woodlands and Agnes Banks Woodlands grow on acidic, nutrient poor soil which acts as a buffer to exotic weed invasion (Benson, 1992). The exotic weeds of the surrounding sandstone areas are not prevalent on the Cumberland Plain.

Dumping of garden waste has the capacity to introduce weeds. Prickly pear (Opuntia sp.) and Cootamundra wattle (Acacia baileyana) were both found in the area growing near piles of waste.

African Lovegrass (Eragrostis curvula) and is widely spread along the roadsides in Western Sydney and has been declared noxious in 18 council areas in NSW (Dean, 1987). Its natural attributes of copious seed production, vigorous seedling growth and its ability to reduce drainage efficiency make it an invasive problem (Dean, 1987).

Whisky grass (Andropogon virginicus) is also common on roadsides and disturbed areas in the region. It has invaded some of the Swamp Woodland which merges with the Castlereagh Scribbly Gum Woodland (Benson, 1992).

At present these species do not pose a major threat to any populations but they do occur in the area. A bush regeneration strategy should be implemented to prevent the situation from worsening.

1.10. Existing Conservation Measures

1.10.1. Propagation

Mt Annan Botanic Garden have collected P. nutans from the Taubmans Factory at Villawood, Readymix Sandmine at Londonderry, and the corner of Government and Spence Roads at Berkshire Park. Propagation of this material has been successful from cuttings (Armstrong, pers.comm.). Accessions are being held at the garden. These are not considered adequate as ex-situ stock for conservation purposes, but are still worth noting and may be required in the future.

1.11. Biodiversity Benefits

The conservation of P. nutans is important in maintaining the biodiversity of the remaining Cumberland Plain woodland in which it occurs. Several other nationally threatened and numerous regionally significant plant species occur in association with P. nutans.

The most significant of these are Allocasuarina glareicola and Pultenaea parviflora which are both Schedule 1 (Endangered) Species under the Threatened Species Conservation Act, 1995. Micromyrtus minutiflora and Dillwynia tenuifolia, both Schedule 2 (Vulnerable) Species, are also commonly found with P. nutans.

1.12. Recommendations

Based on the current information available the following research and management actions are recommended.

1.12.1. Recommendations for Research

  • Survey potential habitat for new populations.
  • Research the recruitment and mortality of populations, including seedbank dynamics and the effects of fire on P. nutans.
  • Research the flowering and fruiting phenology and fecundity, breeding system, and the effects of post-dispersal predation on P. nutans.

1.12.2. Recommendations for Management

  • Development of adequate planning controls to conserve populations, including voluntary conservation agreements, additions to and creation of national parks and/or nature reserves for areas containing P. nutans.
  • Prepare and implement bush regeneration programs.
  • Establish ex-situ storage of seed from immediately threatened populations.
  • Development of a community awareness and support program for the conservation of P. nutans.
  • Preparation of a Species and Habitat Management Plan.