Three Springs Daviesia Daviesia bursarioides Interim Recovery Plan 2004-2009

Western Australian Threatened Species and Communities Unit (WATSCU)
© The Western Australian, Department of Conservation and Land Management, 2004

1. Background

History

Daviesia bursarioides was first collected by W.E. Blackall between Coorow and Arrino in 1932. Further collections were made in 1958 by R.T. Lange, and in 1972 and 1973 by C. Chapman. The sites were re-visited in 1978 but only one surviving population containing 3 plants (Population 1a) was located. This population was damaged in 1979 by construction of a fence between the narrow road verge and the adjacent paddock, but several plants regenerated and recruitment of seedlings occurred following this disturbance.

Since 1993, Charles Strahan (Gardener, Shire of Three Springs) has located four new populations. Three occur on road verges and the fourth population of over 30 plants is on private property. Part of this land is accessed by the Shire for gravel extraction, and protocols are in place to minimise impact on this species. Daviesia bursarioides occupies previously disturbed areas at this site, rather than adjacent undisturbed areas of native vegetation. A sixth population was located on a Nature Reserve in 1997 by D. Papenfus. A translocation commenced at this site in 1998.

It is probable that the species is naturally geographically restricted to the Three Springs area and extensive vegetation clearance has significantly reduced available habitat. Due to the small size of all known populations and the occurrence of most populations in narrow areas of habitat adjacent to roads, it is particularly vulnerable to weed invasion and damage by road maintenance, fire and grazing.

Description

Daviesia bursarioides is a straggling, divaricately branching shrub to 2 m tall, with blue-green spine-tipped branches. The leaves are distinctive among Daviesias, being scattered and small (measuring up to 20 x 2.5 mm) obovate in shape narrowing to the base. The flowers appear between July and September, and are grouped in 3-8 flowered racemes in the axils of the leaves, on a long stem to 35 mm, giving the raceme an open appearance. Flowers are small and typically pea-shaped. Each flower has an upper standard petal 7 x 9 mm, yellow in colour and maroon towards the base. The wing petals are 6 x 3 mm and deep pink, and the keel is 5 x 2 mm, and maroon in colour. The fruit is a triangular pod, 9 mm x 10 mm (Patrick and Brown 2001; Crisp 1995).

Distribution and habitat

Daviesia bursarioides is endemic to the Three Springs area of Western Australia, and is known from approximately 120 plants in six populations over a range of about 15 km. Populations occur on Shire road reserves, Main Road reserves, private property and a Nature Reserve.

Daviesia bursarioides is found in open shrub mallee habitat dominated by Eucalyptus gittinsii, Allocasuarina campestris, Dryandra spp., Hakea spp., and Grevillea spp. Soils are shallow brown sandy loams with extensive lateritic gravel. Population 5 (the largest population) occurs on the periphery of a dense Allocasuarina campestris thicket on deep lateritic gravel. Species diversity at most sites is poor, and the nutrient levels in the soil are low. An analysis of soil from one population indicated that pebbles greater than 2 mm comprised 44% of the sample, and of the remainder, 85.5% was sand. All nutrients analysed (nitrogen, phosphorus and potassium) were present in extremely small quantities (Schwarten 1995).

Biology and ecology

Schwarten (1995) found that Daviesia species first produce seed when three years old. Daviesia bursarioides and other Daviesia species often die after 8-10 years. It appears that after six years the plant crown starts to die, sometimes very rapidly, which affects plant growth, assimilation, flower production and therefore reproductive success.

Daviesia bursarioides responds to disturbance, as do many species of the genus Daviesia. In the largest population, plants that were found growing in disused areas of a gravel pit were more abundant and vigorous than those observed in the adjoining remnant vegetation, and seedlings have been observed after soil disturbance such as roadworks and fence construction. Schwarten (1995) recommends some form of disturbance every 6-8 years as a management technique for Daviesia species, after seed-set has occurred (approximately 3 months after flowering, or longer if the season is particularly hot and dry). This would optimise management of young seed with relatively high viability, and minimise predation of seed by vertebrates and insects. If flowering occurs early in the season (July), seed-set may have occurred by October, when fire may be utilized to stimulate germination, under appropriate weather conditions. If seed-set does not occur until later in the summer, fire may not be an appropriate tool for stimulating germination, and mechanical disturbance of the topsoil, or another similar method, may be a better alternative.

The specific response of Daviesia bursarioides to fire is unknown. Fire is usually a stimulus for regeneration from seed in most Australian legumes (Crisp 1985). Schwarten (1995) found that several Daviesia species had a significant decrease in germination after treatment with various levels of smoke. He suggested that it may be the heat of a fire rather than chemicals in the smoke that breaks the dormancy of Daviesia seed, and that scarification of the seed coat during mechanical disturbance is also effective in stimulating germination.

Most Daviesias are adapted for bee pollination. Daviesia bursarioides is a good food resource for native bees and European honey bees, as the peduncles are sticky from early in the flowering season through to the end of seed set. Daviesia seeds have a starchy elaisome which makes the seed attractive to ants and a range of vertebrates. Seeds collected by ants are usually stored below the soil surface. The seed bank in the top-soil around the plants contains a small number of seeds but it is assumed that most of the seed produced is stored at depth without contributing to the viable seed bank. Seed buried by ants in deeper profiles of the soil may be more immune to predation but it is not clear if this seed is returned to germination depth (Schwarten 1995).

Daviesia bursarioides has a very low seed set, possibly as a result of a decline in pollinators. Schwarten (1995) observed a fruit:flower ratio (F:F) of 3.8% and a seed:ovule (S:O) ratio of 1.9%, meaning that approximately 98% of ovules were aborted. Ratios were calculated for Daviesia spiralis over the course of a flowering season, and it was found that the S:O ratio declined from 3.89% in early flowering season (October) to 0.47% in late flowering season (December). This may reflect the influence of hot, dry periods in decreasing seed production, and/or a preferential nutrient supply within the plant to keep developing existing seed (Schwarten 1995).

Staff from CALMs Threatened Flora Seed Centre (TFSC) have conducted germination trials on Daviesia bursarioides seed over a number of years. Germination levels have varied from 6-80% initially (mean ca. 50%), with tests conducted after seed has been stored for 12 months showing germination of 50-100% (mean ca. 75%) (unpublished data Anne Cochrane, Manager, CALM's Threatened Flora Seed Centre).

Schwarten (1995) studied the longevity of Daviesia bursarioides seed over a 12 month period. He found that 100% of buried seed remained viable after 6 months, with seed showing a slight reduction in size. The seed coat of viable seed became harder over time and the embryo was green, whereas nonviable seed had a soft seed coat and the embryo was yellow. Viability of D. bursarioides seed was reduced to 65% after being buried for 12 months. Seed bags were also fixed to the soil surface in full sun or part shade, but all were eaten by vertebrates within three weeks of setting up the experiment. Whether the rate of decline observed in buried seed continues over time or plateaus, and if so for how long, is essential knowledge for the management of this species and other endangered Daviesias.

Daviesia bursarioides was found to be highly susceptible to infection by the plant pathogen Phytophthora cinnamomi (dieback) when tested by CALM Science Division (Shearer, Crane and Cochrane, submitted). This finding is preliminary as the number of replicates has necessarily been low. If monitoring suggests that dieback may be present in the habitat of D. bursarioides, formal testing for presence of Phytophthora species should be conducted as a matter of urgency.

Schwarten (1995) suggests that all Daviesia species thrive more in an open stand in full sun without dominance of taller species. He suggests that Daviesia bursarioides plants growing under Allocasuarina campestris plants suffer greatly from a lack of light and water, responding with slow growth and even lower seed set. The short life cycle of D. bursarioides in combination with low number of years of seed production, low levels of seed set each year and potentially short term viability of seed all indicate that this species will require ongoing active management to ensure its survival.

Threats

Due to the low number of plants and the threats associated with growing mainly on narrow, degraded road reserves, Daviesia bursarioides was declared as Rare Flora in September 1987 and ranked as Critically Endangered under the Wildlife Conservation Act 1950. D. bursarioides is also listed as Endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). D. bursarioides currently meets Red List (IUCN 2000) Category CR under criteria B2ab(iii); C1+2a(i) due to the highly fragmented populations, low number of plants, and continuing decline in the quality of the habitat. It has a highly restricted distribution in a widely cleared landscape. The main threats are edge effects, degraded habitat, road, fence and firebreak maintenance, weed invasion, competition due to shading (this may be occurring as a consequence of a disturbance regime that is not particularly favorable to D. bursarioides), inappropriate disturbance regimes and disease.

  • Edge effects severely affect narrow linear populations such as those on road reserves through exposure to influences from adjacent cleared land. In addition to the proximity of a weed seed source, effects include increased wind speed, fertiliser and herbicide spray drift and runoff, modified hydrology and altered disturbance regimes, including fire.
  • Degraded habitat represents a threat to all roadside populations, which occur on narrow reserves with cleared land beyond. The lack of associated native vegetation increases the likelihood that pollinators will be infrequent or absent. In addition, the lack of available habitat for recruitment is of concern.
  • Road, firebreak and fence maintenance activities have the potential to threaten existing plants. Threats include grading, chemical spraying, construction of drainage channels, the mowing of roadside vegetation and movement of machinery. Several of these actions also encourage weed invasion. However, soil disturbance by machinery often stimulates germination of seed in this species. Road maintenance has damaged existing Daviesia bursarioides plants in the past, but CALM Moora District staff and Shire of Three Springs operational staff have a very effective working relationship, and this threat has therefore been minimised. Currently proposed roadworks will involve a slight realignment to accommodate this species, and soil displaced will be used in the rehabilitation of cleared areas adjacent to Population 2.
  • Gravel extraction has the potential to threaten Population 5. However, the Shire of Three Springs operational staff are aware of this population and have guidelines in place to minimise impact on this species when extracting gravel from this area.
  • Weed invasion and competition is a threat to roadside populations, although current weed levels are low. The populations all occur in very narrow (3-4 m wide) road reserves that are adjacent to cleared farmland or wide firebreaks. These populations are constantly being invaded by weed seeds blown in from adjoining paddocks. The hard, impoverished soil protects the populations to a certain extent, limiting the level of weed invasion.
  • Shading and competition from associated Allocasuarina campestris has been said to detract from the health of the Daviesia bursarioides causing slower growth and lowering seed set. Schwarten (1995) suggested that all Daviesias grew best in an open position, and that the Allocasuarinas crowding these plants should be cut back.
  • Inappropriate disturbance regimes (by fire or machinery) may affect the viability of populations, as these kill adult plants but stimulate germination in Daviesia bursarioides. If this is the case, the soil seed bank would rapidly be depleted if these events recurred before regenerating or juvenile plants reached maturity and replenished the soil seed bank. However, an absence of disturbance for too long will reduce germination events and therefore recruitment, possibly causing the extinction of a population if the interval between disturbance events exceeds the longevity of soil-stored seed.
  • Disease could be a serious threat to populations, as this species has been found to be highly susceptible to the plant pathogen Phytophthora cinnamomi (dieback). This plant pathogen causes the roots to rot and results in death from drought stress. The pathogen is not known to be present in the vicinity of populations, but will require careful management if future monitoring indicates that it is present. It is possible that areas subject to ponding, even in relatively dry areas such as the natural habitat of this species, are conducive to the introduction, spread and amplification of the disease.
  • Grazing by kangaroos impacted heavily on juveniles translocated into Population 6T in 1999 and 2000. Mature Daviesia bursarioides plants are spiny and not subject to grazing, but young seedlings are vulnerable. Grazing of juveniles was not marked in 1998, suggesting that grazing pressure varies according to the availability of alternative feed.

Summary of population information and threats

Pop. No. & Location Land Status Year/No. plants Condition Threats
1a. S of Three Springs Shire road reserve 1984 11
1991 11 (2)
1994 19
1999 9
2000 12
Healthy Road and fence maintenance, weed invasion, edge effects, degraded habitat, inappropriate disturbance regimes
1b. S of Three Springs Private property 1984 1 Moderate Fence maintenance, weed invasion, edge effects, degraded habitat, inappropriate disturbance regimes
2. Three Springs Shire road reserve 1993 4
1994 6 (5)
2000 4
2002 1
2003 2 (7)
Moderate Road and fence maintenance, weed invasion and competition, edge effects, degraded habitat, inappropriate disturbance regimes
3. N of Three Springs MRWA road reserve 1993 5
1994 5+ (12)
2000 15
Moderate Road and fence maintenance, weed invasion and competition, edge effects, degraded habitat, inappropriate disturbance regimes
4. N of Three Springs MRWA road reserve 1994 9 (3)
2000 11
2002 5
Moderate Road and fence maintenance, weed invasion and competition, edge effects, degraded habitat, inappropriate disturbance regimes
5. SW of Three Springs Private property 1995 60+
2001 35+
Healthy Gravel extraction, fence maintenance, weed invasion and competition, shading and competition, inappropriate disturbance regimes
6. W of Three Springs Nature reserve 1997 4
1998 12
2000 14
Healthy Firebreak maintenance, weed invasion, inappropriate disturbance regimes
6T. W of Three Springs Nature reserve 1998 (192)
1999 (47+144)
2000 (46+22+262)
2001 (41+20+13)
2002 37 (16+5)
Healthy Grazing by kangaroos, inappropriate disturbance regimes

Numbers in brackets = number of juveniles. Plants in 6T are listed by year of planting; (ie in order figures represent: numbers of plants from 1998 planting + from 1999 + from 2000); MRWA = Main Roads Department of Western Australia.

Guide for decision-makers

Section 1 provides details of current and possible future threats. Any on-ground works (clearing, firebreaks, roadworks etc) in the immediate vicinity of Daviesia bursarioides will require assessment. On-ground works should not be approved unless the proponents can demonstrate that they will not have an impact on the species, or on its habitat or potential habitat.

Critical habitat

Critical habitat is habitat identified as being critical to the survival of a listed threatened species or listed threatened ecological community. Habitat is defined as the biophysical medium or media occupied (continuously, periodically or occasionally) by an organism or group of organisms or once occupied (continuously, periodically or occasionally) by an organism, or group of organisms, and into which organisms of that kind have the potential to be reintroduced (Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)).

Daviesia bursarioides is listed as Critically Endangered, and it is therefore considered that all known habitat for wild and translocated populations is critical habitat. This includes:

  • the area of occupancy of wild and translocated populations;
  • areas of similar habitat within 200 metres of populations, i.e. yellow sand or brown sand with gravel in low scrub or heath (these provide potential habitat for natural range extension);
  • corridors of remnant vegetation that link populations (these are necessary to allow pollinators to move between populations and are usually road and rail reserves);
  • additional occurrences of similar habitat that do not currently contain the species but may have done so in the past (these represent possible translocation sites).

Benefits to other species or ecological communities

There are no other known listed threatened species or ecological communities in the habitat of Daviesia bursarioides. However, recovery actions such as improving the security of tenure of D. bursarioides populations will also help protect the habitat in which the populations are located.

International Obligations

This plan is fully consistent with the aims and recommendations of the Convention on Biological Diversity, ratified by Australia in June 1993, and will assist in implementing Australias responsibilities under that convention. The taxon is not listed under any specific international treaty, however, and therefore this IRP does not affect Australias obligations under any other international agreements.

Role and interests of indigenous people

Indigenous communities interested or involved in the areas affected by this plan have not yet been identified. The Aboriginal Sites Register maintained by the Department of Indigenous Affairs does not list any significant sites in the vicinity of these populations. However, not all significant sites are listed on the Register. Input and involvement will be sought from any indigenous groups that have an active interest in the areas that are habitat for Daviesia bursarioides, and this is discussed in the recovery actions.

Social and economic impacts

The implementation of this recovery plan has the potential to have some limited social and economic impact, where populations are located on private property. One population of Daviesia bursarioides occurs on private land, in an area previously used as a source of gravel, and negotiations will continue with regard to the future management of this population. In addition, the Nature Reserve used for the translocation must be accessed through private property. Recovery actions refer to continued liaison between stakeholders with regard to these areas.

Evaluation of the Plans Performance

CALM will evaluate the performance of this IRP in conjunction with the Moora District Threatened Flora Recovery Team. In addition to annual reporting on progress with listed actions and comparison against the criteria for success and failure, the plan is to be reviewed within five years of its implementation.