Peas (Swainsona Species)
Total Page：16
File Type：pdf, Size：1020Kb
Action Statement Flora and Fauna Guarantee Act 1988 No. 126 Twelve threatened Swainson-peas and Darling- peas (Swainsona species) Description and distribution The genus Swainsona is represented in Victoria by Distribution maps of each species can be found at 18 species, of which all but four are considered to the end of this Action Statement. be threatened in the wild. This Action Statement Habitat addresses 12 threatened (vulnerable or endangered) taxa of Swainsona listed below. Swainsona species are confined to specific Detailed survey and monitoring of all known grassland and woodland habitats found in south- populations was undertaken between September west Victoria, the Mallee, native grasslands of the 1997 and September 1999. The information northern plains, and riverine habitats along the presented in this Action Statement is based on Murray River. results of these surveys which are stored on the Department of Sustainability and Environment Life history and ecology threatened plant population monitoring database, Swainsona species are largely renascent perennials, VROTPop. Of the two remaining threatened resprouting in suitable conditions from a Swainsona species, Swainsona galegifolia already persistent rootstock. This gives individual plants has a published Action Statement, while Swainsona the capacity to persist between years given suitable recta is presumed extinct in Victoria. conditions. Walsh et al. (1996) also comment that Swainsona species are small to medium annuals or Swainsona purpurea can behave as an annual. renascent perennials, with hairy to glabrous, Growth and flowering among most species of pinnate foliage with 3 - 7 linear leaflets, and Swainsona species appears to be stimulated by flowers arranged in racemes (on lateral stalks) available moisture, thus plants are most frequently varying from yellow to red, pink, purple or violet in observable following adequate Spring rainfall. colour. Individual species’ descriptions may be found in the Flora of Victoria, Volume 3 (Walsh and Exceptions include Swainsona adenophylla, which Entwisle 1996). has not been reliably observed in Victoria since 1980 (Chesterfield et al.), Swainsona luteola which The Swainsona species addressed in this Action also has not been reliably observed for many years, Statement are widely distributed across western and Swainsona pyrophila, a short-lived perennial and northern and Victoria, and many also occur which, as its name suggests (pyros = fire & philos = throughout South Australia, New South Wales, loving), displays a clear association with fire, and Australian Capital Territory and Queensland. appears to grow for only 1 to 2 years after fire Historical records suggest that many Swainsona (Scarlett and Parsons 1993). Plants are usually species have become significantly reduced in seen in the first Spring following a fire. Soil Victoria and elsewhere, both in number and disturbance will also often stimulate germination. geographic extent, with many occurrences dating back to the 19th century now believed to be extinct. All species observed during this study (Spring ecosystems. Plants perform better in an environment 1999) produced copious flowers and similarly where there are gaps in the herb layer, high light abundant quantities of seed, though significant intensity and low competition from other plants. variation in flowering and seed production occurs Despite the abundance of seed produced by according to seasonal conditions. Flowering and Swainsona species, the incidence of recruitment by seed production is apparently only curtailed when this means is believed to be irregular and not plants begin to dry off from insufficient moisture. great. Scientific data specifically about persistence Vegetative reproduction appears to be the most of viable seed-banks, and germination of common method of reproduction in Swainsona Swainsona seed is limited. greyana, Swainsona purpurea and Swainsona A recent study by Capuano (1993) investigating sericea (in Mallee populations). The latter species, seed ecology of Swainsona plagiotropis found that where it occurs on the Northern Plains, exhibits only a small proportion of seed recovered from the none of the rhizomatous habit observed in Mallee soil was in fact viable (1 seed from a sample of 9). populations. Significant increases in germination of seeds Swainsona species, like other members of the Pea treated by scarification, and in those exposed to family (Fabaceae), produce hard-coated seeds temperatures up to 70oC, were recorded in this which frequently require some treatment to break study, giving some support to the idea that seed dormancy. It is surmised that heat treatments, treatment or disturbance is a necessary precursor including fire or extreme soil temperatures, and to seedling recruitment in Swainsona species. physical disturbances such as soil scraping which Scarlett and Parsons (1993) speculate that a can rupture the seed coat, are required in gradual depletion of the soil-stored seedbank of conjunction with moisture to stimulate Swainsona pyrophila may be occurring in the germination. absence of regular fires in its preferred habitat. The foliage and flowers of Swainsona species are highly palatable to grazing animals. Although Conservation status Swainsona species are adversely affected by Each species has been listed in Table 1 by its status intense and continuous grazing by stock, rabbits or under the Environment Protection & Biodiversity native herbivores, particularly in Spring flowering Conservation Act 1999 (EPBC), its status within and seeding periods, it appears that light grazing Victoria (DSE), and its status under the Flora and at other times in their lifecycle can benefit the Fauna Guarantee Act 1988 (FFG). plants. Growth of Swainsona species appears to be more vigorous in sites with an open understorey, consistent with many native species in grassy Table 1: Conservation Status Scientific name EPBC DSE FFG Swainsona adenophylla eL Swainsona brachycarpa vL Swainsona greyana eL Swainsona luteola eL Swainsona murrayana VeL Swainsona phacoides eL Swainsona plagiotropis VeL Swainsona purpurea eL Swainsona pyrophila VvL Swainsona reticulata vL Swainsona sericea vR Swainsona wainsonioides eL Abbreviations: EPBC: Status under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999: V = vulnerable in Australia; DSE: Status according to Advisory List of Rare or Threatened Vascular Plants in Victoria – 2003: e = endangered in Victoria; v = vulnerable in Victoria; FFG: Status under the Victorian Flora and Fauna Guarantee Act 1988: L = listed as threatened, R = Recommended for listing as threatened. 2 Decline and threats numbers are expected as farming practices change (S. Diez pers. comm.). The Grampians Swainsona plagiotropis plants are confined almost Recreational damage from vehicles is a minor exclusively to freehold land (88.6%), roadsides, rail problem at specific sites. In the Grampians, reserves and cemeteries (8.5%), or Commonwealth Swainsona brachycarpa is known from only five land (Echuca airport) (2.8%). Although the total populations within a restricted area. There is no population number for Swainsona plagiotropis is evidence that populations are declining, rather it estimated to be ca 170 000, there is a continuing appears that Swainsona brachycarpa is just decline in population numbers. Of 50 recorded extremely rare in Victoria. Apart from the small populations, only 36 are still believed to be extant. number and size of populations, Swainsona The majority of populations occur in areas of <5ha, brachycarpa faces no major threats. Competition and are highly susceptible to a range of potentially for light and nutrients with other grasses and devastating threats. Over 50% of plants grow in an herbs is a potential threat. Recreational damage area of <30ha, on a freehold property at Patho. from vehicles is a minor problem at some sites. The absence of significant populations of Swainsona plagiotropis in conservation reserves is Wimmera and Northern Plains a major limitation for its future survival. In the Wimmera and Northern Plains the Principal threats to Swainsona plagiotropis include widespread decline in Swainsona species mirrors inappropriate grazing regimes, intensive cropping the fate of temperate grasslands in south eastern and pasture improvement. At some sites the Australia. decline in Swainsona plagiotropis is attributed to a lack of disturbance, resulting in increased The decline in population and plant numbers is a competition from weeds and grasses. Insect recent (post-European) phenomenon, attributable predation has also been noted to have a serious largely to loss of habitat in developing agricultural impact on populations where grass cover is dense, landscapes, compounded by subsequent and adjacent to cropped areas (O’Brien and Diez management regimes, including intensive stock 1997). grazing, cropping, irrigation, pugging in wet weather, pasture improvement, road improvement, The recent declaration of Terrick Terrick National weed management. On roadsides, rail reserves, Park has secured Swainsona murrayana in and some public land reserves, plants are Victoria. Over 45% of known plants, (>42 000 threatened by a lack of disturbance, which individuals), are included within the Park prevents gap formation and increases competition boundary, and management is, of course, primarily for light and other resources from weeds. Grazing concerned with biodiversity conservation. A by rabbits or hares is also a threat at