Academic literature on the topic 'Bursaria spinosa'

Bursariais an endemic Australian genus of mostlyspinescent, scruffy shrubs and trees, found in all but the most arid or alpineareas. Previous classifications include many infraspecific taxa and haveproved unworkable in eastern Australia. This paper presents a revision of thegenus. On the basis of phenetic analyses of morphometric characters thefollowing taxa are now recognised: B. calcicolaL.Cayzer, Crisp & I.Telford, B. incana Lindl.,B. longisepala Domin,B. occidentalis E.M.Benn.,B. reevesii L.Cayzer, Crisp & I.Telford,B. spinosa Cav. subsp. lasiophylla (E.M.Benn.) L.Cayzer, Crisp & I.Telford, B. spinosasubsp. spinosa and B. tenuifoliaF.M.Bail. Two are described as new(B. calcicola, B. reevesii), and one is changed in rank:B. spinosa subsp. lasiophylla(formerly B. lasiophylla E.M.Benn.). None of the otherinfraspecific taxa recognised previously is supported by our analyses.

Grassy woodlands worldwide are vertically structured by trees, a ground layer of grasses and forbs, and a variable mid-storey. In Western Sydney’s Cumberland Plain Woodland this mid-storey is increasingly dominated by the prickly shrub Bursaria spinosa Cav. subsp. spinosa. We investigated whether tree and shrub vegetation affects species richness and composition of ground layer microhabitats in this woodland, and whether fire frequency directly affects the ground layer in addition to any indirect effects via overstorey vegetation. Replicate sites were located in areas that had burnt with a frequency that was high, moderate or low. All sites had a similar time since last fire. Three microhabitats (open, under Bursaria, around tree) within each site were sampled for species richness and composition of native and exotic species. Native species richness was not significantly affected by either microhabitat or fire frequency, for total species, grasses or forbs; however the relative abundance of native grasses decreased significantly as fire frequency declined, while the relative abundance of native forbs increased. Exotic species richness was lowest at high fire frequency and significantly higher at low fire frequency. Species composition was significantly affected by both microhabitat and fire frequency combining independently. Planned burning at relatively short intervals can help managers retain grassy habitat for open patch species, habitat for ground layer species that do best under frequent fire, and a robust Themeda triandra Forssk. sward antagonistic to weeds.

We provide a summary of two recent studies that investigated the role that three native insectary plants can play in promoting predatory arthropods, and thereby to enhance biological control of vineyard pests in Australia. Native plants are preferred as supplementary flora, as they are locally-adapted to Australia's climatic conditions. Stands of mature Bursaria spinosa, Leptospermum continentale and Rytidosperma ssp. located adjacent to, or in vineyards, in South Australia were sampled for arthropods in 2013/14. Grapevines were also sampled to explore relationships between each plant and associated arthropods using common diversity indices. Twenty seven thousand and ninety-one individual invertebrate specimens were collected, comprising 20 orders and 287 morphospecies. These were categorised into functional groups of predators, herbivores and other. Predatory arthropods dominated the diversity of morphospecies present on each plant. The richness of predator morphospecies across all plant types was nearly double the number found in association with grapevines. It may be possible to increase the functional diversity of predatory arthropods by more than 3x when either B. spinosa or L. continentale is present versus grapevines only, and increase the net number of predator morphospecies by around 27% when Rytidosperma ssp. are planted in combination with grapevines. The selected plants provide a suitable habitat to support diverse and functional populations of predatory arthropods. The opportunity to plant selected native insectary species could help wine grape growers save time and resources by producing fruit with lower pest incidence, while enhancing biodiversity associated with vineyards.

Browsing cascades have strong implications for biodiversity conservation and fire management. The associational resistance and associational susceptibility hypotheses suggest different mechanisms. We tested the veracity of these two hypotheses by using small dry eucalypt forest and woodland trees. At 67 sites, we measured the height of the browse line and estimated the proportion of foliage remaining below it for all adult individuals of small trees within a 50 × 50 m area, recorded scat numbers, browsing damage to tree seedlings by species and environmental data. The 110–130-cm browse line, and strong relationships between macropod scat numbers and the remaining foliage below the browse line, suggested that Bennetts wallabies (Macropus rufogriseus Shaw) were the main cause of umbrella-shaped trees. The browsers preferred Exocarpos cupressiformis Labill. and Bursaria spinosa Cav. At the other extreme, adult Acacia dealbata Link suffered no browsing damage. All species were browsed as seedlings. Associational resistance occurred in some species and associational susceptibility in others, with the degree of difference in palatability between alternative sources of browse possibly resolving this apparent contradiction. Low browsing pressure is likely to cause woody thickening, an increase in fire hazard and a decrease in biodiversity. Extremely high browsing pressure had no such effects.

This study investigated the role that native insectary plants can play in promoting predatory arthropods, and thereby to enhance biological control of vineyard pests in Australia. I also set out to clarify if light brown apple moth (LBAM), Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae) is the main lepidopteran pest of grapevines in vineyards. Economic damage is caused to grapevines each season by pest species and E. postvittana is considered the dominant insect pest in Australian vineyards. However, recent observations suggested that species of tortricids other than E. postvittana may also act as pests. I investigated which tortricids are present in local vineyards, and whether the diversity of tortricids varied significantly among vineyards. I used molecular methods to determine the species of tortricids present in the canopies of grapevines over two growing seasons. This study confirms that E. postvittana is the most common tortricid pest in South Australian vineyards. Acropolitis rudisana (Walker) (Lepidoptera: Tortricidae), lucerne leafroller, Merophyas divulsana (Walker) (Lepidoptera: Tortricidae), and cotton tipworm, Crocidosema plebejana (Zeller) (Lepidoptera: Tortricidae) are also present in grapevine canopies but have not been reported previously. I also sought to determine if three native candidate native insectary plants, Christmas bush, Bursaria spinosa (Cav.) (Apiales: Pittosporaceae), prickly tea-tree, Leptospermum continentale (Forst. and G.Forst) (Myrtales: Myrtaceae), and wallaby grasses, Rytidosperma ssp. (DC) (Poales: Poaceae) have the capacity to support populations of predatory arthropods throughout the year, and if they may also provide habitat for economically damaging vineyards pests. Surveys were conducted in Adelaide Hills, Barossa Valley and Eden Valley vineyards over a 12-month period. The data were analysed to answer the following questions. What is the biological and functional diversity associated with each plant species? What are the features of an effective, functional native insectary plant assemblage for use in and around vineyards? What is the level of similarity and dissimilarity between the arthropod faunas of each plant species? Each plant species was found to support diverse predator species, which should attack a range of other arthropod pests across their life stages. It may also be possible to increase the functional diversity of predatory arthropods by more than three times when B. spinosa or L. continentale is incorporated into a landscape containing vineyards. Rytidosperma ssp. provides valuable complementary habitat for predatory species other than those commonly found in association with the woody perennials. When Rytidosperma ssp. are included in a viii plant assemblage with each woody plant species, this could result in an average net increase in predator morphospecies richness of at least 27%. Species distribution modelling was used to examine the potential range of each plant species under different climatic conditions. The insectary plants are naturally adapted to all of the major wine growing regions within Australia. Vineyard managers are encouraged to explore the use of B. spinosa, L. continentale and Rytidosperma ssp. as insectary plants in their vineyards. This information could help wine grape growers to manage pests like LBAM, save time and money by producing grapes with lower pest incidence, while enhancing the biodiversity of their vineyards.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 2019