Bushland Weeds Manual - Environmental Weeds Action Network

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38 Chapter 4 Corms, Bulbs and Tubers Box 4.2 Fire and the geophyte weeds Fire is the major disturbance in the Mediterranean ecosystems of South Africa from where 95 % of our bulbous and cormous weeds have come. Consequently many have evolved life history traits that are strongly tied to recurrent fire. Mechanism for survival Dying back to an underground storage organ over the long dry summer is an extremely effective way of surviving fire. Soil offers very effective insulation to the corms or bulbs and some have contractile roots that pull the storage organs of young plants deeper into the soil helping avoid lethal fire temperatures (Bond and van Wilgen 1996). When dormant in summer, most cormous, bulbous and tuberous weeds will probably survive all but the very hottest fires. Dormancy and fire-stimulated flowering Some cormous and bulbous weeds, to varying degrees, are dormant between fires and sometimes between seasons. That is, the corms remain dormant in the soil producing no leaves or flowers during the growing season. Within Cape Tulip populations, for example, up to 60 % of corms may be dormant in any one season. Fire often brings most corms out of dormancy but seasonal conditions including soil temperature and rainfall also play a role (Parsons and Cuthbertson 2001). Others flower particularly well following fire with fire-stimulated flowering commonly observed among many geophytes where they occur naturally in southern Africa (Goldblatt 1978, Richardson et al. 1984, Le Maitre and Brown 1992). Nearly all species of Watsonia flower profusely following veld fire (Goldblatt 1989). Some, such as Watsonia borbonica, only flower for the first few seasons following fire (Le Maitre 1984). This mass flowering corresponds with prolific seed production. Displays of Gladiolus are also striking in the first few seasons following a burn, particularly in the winter rainfall areas on the nutrient-poor sandstone soils of the Cape Region (Goldblatt and Manning 1998). It is also interesting to note that horticulturists commonly use smoke to induce flowering in South African geophytes with Narcissus tazetta, Freesia and Crinum species all responding favourably (Tompsett 1985, Mathew 1997). Fire-stimulated flowering also appears to occur to some degree among populations of these plants where they are invading the Mediterranean ecosystems of southern Australia. Interestingly both corm dormancy and firestimulated flowering have been recorded in Pink Gladiolus invading Banksia woodland near Perth (Marshall 2001). In the first season following fire workers recorded a mean of 42 flowering plants per one metre square plot. Two years after the fire a mean of only 2.6 flowering plants was recorded. The total number of plants (flowering and non-flowering combined) decreased from a mean of 54 per plot to 7 plants per plot. This work indicates that most corms of Pink Gladiolus seem to go into dormancy between fires. How wide-spread the phenomenon is among weedy geophytes requires further investigation as it has important implications for management and control of cormous and bulbous weeds. Seeds, seedlings and spread Generally the seeds of these plants do not require the smoke or heat of fire for germination. Rather, it is thought that the fire-stimulated flowering is actually linked to favourable post-fire conditions. For cormous and bulbous plants the post-fire environment offers space and light for seed germination and seedling establishment in the absence of larger trees and shrubs (Keeley and Bond 1997, Goldblatt and Manning 1998). With mass flowering and prolific seed production followed by favourable conditions for seed germination and seedling establishment, fire appears to be one of the major factors facilitating the establishment of many of these weeds into otherwise undisturbed bushland. A window of opportunity Pink Gladiolus flowering in the spring season following a summer fire in Banksia woodland at Shenton Bushland. Fire however also offers a significant opportunity to control bulbous, cormous and tuberous weeds in bushland. Following a summer fire these weeds will often emerge in autumn, prior to regeneration of native vegetation. The plants are clearly visible and the resprouting flowering bulbs, corms and resprouting tuberous mats of bridal creeper are an easy target for herbicide control. Control of established populations and prevention of seed production and further spread are achievable. It is an ideal time to control those species such as Cape Tulip and Pink Gladiolus that are largely dormant between fires. Additional resources should always be made available to control bulbous, cormous or tuberous weeds following fire.
Management and control Stopping the spread • Understand the distribution of the weed across the bushland by mapping the spread. This is an important first step (chapter 7). Maps are the basis for any strategy to limit further spread and contain existing populations. • Target small populations in good bush and the outliers of dense infestations (use the maps). • Determine if paths and water run-off are contributing to spread of cormels, bulbils or seed. • Determine whether the sources of infestations are old soil or rubble dumps. Sometimes the only option may be physical removal of these dumps (Box 4.3). • Avoid removing plant material at times of seed or cormel production. • Avoid working in areas where weeds are actively shedding seed. • Control in the season immediately following fire will prevent seed set in established plants, reduce seedling establishment in the post fire landscape and prevent expansion of existing populations. Chapter 4 Corms, Bulbs and Tubers Physical removal Although hand-removal can be very labour intensive and ties up a lot of resources it is often the most appropriate and sometimes the only method of control available. It is particularly appropriate for small isolated populations in good bushland. Targeting these isolated populations of weeds in good bushland and preventing their establishment and spread is the key to protecting undisturbed plant communities. Minimising soil disturbance Physically removing weeds with fleshy underground storage organs requires extreme care in handling. Soil disturbance can lead to the establishment of other weeds, particularly annual herbs (Hobbs and Atkins 1988, Hobbs 1991). In Shenton Bushland the soil disturbance caused by physical removal of Yellow Soldier bulbs caused an increase in the cover of annual weeds such as Flat Weed (Hypochaeris glabra) and French Catchfly (Silene gallica). To try and minimise soil disturbance a range of tools are used for physically removing bulbous, cormous and tuberous weeds. Such tools include sharp knives, long screwdrivers and narrow trowels for smaller plants such as Freesia and Harlequin Flower and specially designed ‘Peter levers’ for Watsonia and Arum Lily. Box 4.3 Dealing with sources of weed invasion into undisturbed bushland. Old rubble/garden refuse dumps throughout Shenton Bushland appear to be one of the major sources of cormous and bulbous weed invasion into undisturbed bushland. In late winter 2000 the Friends, City of Nedlands with a group of community service workers, Green Corps and EWAN, removed one such dump that appeared to be the source of Freesia invasion into the Banksia woodland at Shenton Bushland. The operation took five working days and involved moving around 30 cubic metres of rubble, taken away for deep burial at a tip site. The remaining bare ground was direct seeded with species of native herbs, shrubs and a few trees. The seed was collected from adjoining Banksia woodland. The following autumn Slender Podolepis (Podolepis gracilis), Prickly Moses (Acacia pulchella), Native Wisteria (Hardenbergia comptoniana) and Jarrah (Eucalyptus marginata) were among the species germinating on the removal site. A few annual weeds were also present. Green Corps team starting to remove the soil dump . The site on completion of removal. 39
Page 1 and 2: Bushland Weeds A practical guide to
Page 3: Acknowledgments This manual is the
Page 6 and 7: iv Introduction The Banksia, Tuart
Page 8 and 9: 2 Chapter 1 The Project Blue Gum La
Page 10 and 11: 4 Chapter 1 The Project Both Arum L
Page 12 and 13: 6 Chapter 2 Managing Weeds in Bushl
Page 14 and 15: 8 Chapter 2 Managing Weeds in Bushl
Page 16 and 17: 10 Chapter 3 Grass Weeds Many grass
Page 18 and 19: 12 Chapter 3 Grass Weeds Box 3.3 Gr
Page 20 and 21: 14 Chapter 3 Grass Weeds • Transi
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Page 24 and 25: 18 Chapter 3 Grass Weeds Rhizomatou
Page 26 and 27: 20 Chapter 3 Grass Weeds Case Studi
Page 34 and 35: Chapter 3 Grass Weeds Management Ta
Page 36 and 37: Chapter 3 Grass Weeds Management Ta
Page 38 and 39: 32 Chapter 4 Corms, Bulbs and Tuber
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Page 60 and 61: Iridaceae Moraea miniata Two Leaf C
Page 62 and 63: Chapter 5 Broadleaf Herbs, Sedges a
Page 64 and 65: 58 Chapter 5 Broadleaf Herbs, Sedge
Page 72 and 73: Chapter 5 Annual Broadleaf Herbs, S
Page 74 and 75: Chapter 5 Annual Broadleaf Herbs, S
Page 76 and 77: Chapter 5 Perennial Broadleaf Herbs
Page 78 and 79: Chapter 5 Perennial Broadleaf Herbs
Page 80 and 81: 74 Chapter 6 Trees, Shrubs and Clim
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Chapter 6 Trees, Shrubs and Climber
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90 Chapter 7 Weed Mapping in Remnan
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92 Chapter 7 Weed Mapping in Remnan
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94 Chapter 8 Herbicide Use in Bushl
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100 Final Note In the end, environm
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102 References 1 Aarssen, L.W., Hal
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104 References 101 Dixon, B. (2002)
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106 References 204 Mann, R. (1998)
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108 307 The Nature Conservancy (200
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