Health and distribution of the Snow Gum Eucalyptus pauciflora ssp. pauciflora in the Ballarat region of Victoria Kristin Monie 265920 Travis Turner 265987 Melbourne School of Land and Environment The University of Melbourne Abstract Fifty-three remnant Snow Gum E. pauciflora ssp. pauciflora sites were assessed within a 40 km radius of Ballarat, Victoria. Thirty sites were part of the 1996 study by Baker, which enabled comparative statistical analysis. Sites were located across various land tenures and soil types, where data was collected on a range of variables contributing to the health and distribution of Snow Gums. Site assessments were conducted from March-August 2008. Snow Gums were located on a range of landforms, with a higher proportion found on parallel or convergent slopes which were gently to moderately inclined. All sites occurred on acidic soils across various soil texture groups. Snow Gums sites were found in five Ecological Vegetation Classes with 166 different species, of which 111 were indigenous and 55 were exotic. Most species occurred infrequently across the sites, and a greater cover abundance of natives compared to weeds correlated with mature Snow Gums in better health. Snow Gum individuals in poor health had lighter fruit crops than trees in very good health. Roadside sites had a significantly higher proportion of mature and regenerating individuals, which were also in better health than freehold and crown land sites. Grazing was found to significantly reduce both the health and regeneration of Snow Gums, with fenced sites containing a large proportion of the total number of trees found in good health. Natural disturbance and road works were found to be beneficial, with a high occurrence of regeneration at these sites. Land tenure and grazing were the key determinants of the health and distribution of Snow Gums in the Ballarat region. 1 2 Acknowledgements A number of people played a key role in the development and completion of this industry project, providing a range of intellectual, physical and financial resources. Firstly we would like to thank the industry sponsor, Corangamite Catchment Management Authority, for financial assistance provided for the project. Various academic staff at the University of Melbourne (Melbourne School of Land and Environment) provided invaluable advice and assistance on a range of aspects of the project, including: Ron Teo (soil laboratory testing), Cheryl O’Dwyer (data loggers) and Robert Edis (soil). Biodiversity Staff, including Roger Thomas, also provided valuable assistance with species identification. We would also like to thank our project supervisor, Graham Brodie of the University of Melbourne, for his ongoing patience and valuable feedback throughout the planning, data analysis, drafting and presentation process. And finally we would like to thank our industry mentor, Tim D’Ombrain of Biodiversity Services, for his unfathomable enthusiasm and gracious hospitality throughout the project. Tim provided constant support, guidance and expertise on botanical, ecological and technical aspects of the project, as well as access to a range of resources. 3 4 Table of Contents Abstract 1 Acknowledgements 3 1. Introduction 9 1.1 Factors affecting Eucalyptus pauciflora spp. pauciflora distribution 10 1.1.1 Landform and soil characteristics 10 1.1.2 Vegetation communities and associated species 11 1.1.3 Climate 12 1.1.4 Land use and Competition 13 1.1.5 Mechanisms for regeneration 13 1.1.6 Effective patch size 14 1.2 Factors affecting Eucalyptus pauciflora spp. pauciflora health 15 1.2.1 Soil 15 1.2.2 Associated species 15 1.2.3 Land tenure 15 1.2.4 Grazing 15 1.2.5 Regeneration 16 1.2.6 Isolation – Edge effect 16 1.2.7 Other parameters of interest 17 1.3 Industry relationship 18 2. Project objectives 19 2.1 Effects on the distribution of Snow Gums in the Ballarat region 19 2.2 Effects on the health of Snow Gums in the Ballarat region 19 3. Method 21 3.1 Study sites 21 3.2 Data collection 22 3.2.1 Data sheet 22 3.2.2 Site boundaries 22 3.2.3 Tree assessments 22 3.2.4 Vegetation communities and associated species 23 3.2.5 Soil 23 3.2.6 Additional parameters 24 3.2.7 Data loggers 24 3.3 Data collation and analysis 25 3.4 Mapping 25 4. Results 27 4.1 Distribution of the Ballarat Snow Gums 28 4.1.1 Landform 28 4.1.2 Aspect 29 4.1.3 Soil 29 4.1.3.1 Colour 30 4.1.3.2 Texture 30 4.1.3.3 pH 31 4.1.3.4 Electrical conductivity 32 4.1.4 Vegetation community and associated species 33 5 4.1.4.1 Associated species 33 4.1.4.2 Ecological Vegetation Classes 35 4.1.5 Climate 36 4.1.6 Land use and competition 37 4.1.6.1 Tenure 37 4.1.6.2 Disturbance 39 4.2 Health of the Ballarat Snow Gums 40 4.2.1 Individual Snow Gum health 40 4.2.2 Snow Gum site health 41 4.2.3 Comparison with 1996 Data 41 4.2.4 Mistletoe 42 4.2.5 Flowering 42 4.2.6 Fruit Crop 43 4.2.7 Tree Form 44 4.2.8 Diameter at Breast Height 45 4.2.9 Land Tenure 46 4.2.10 Grazing 48 4.2.11 Fencing 48 4.2.12 Patch size 49 4.2.13 Vegetation community 50 4.2.14 Weeds 52 4.2.15 Soil 53 4.2.16 Regeneration 53 5. Discussion 55 5.1 Distribution of the Ballarat Snow Gums 55 5.1.1 Landform 55 5.1.1.1Site Morphology 55 5.1.1.2 Percentage slope 55 5.1.1.3 Slope curvature 56 5.1.1.4 Influence of slope on regeneration 56 5.1.1.5 Aspect 57 5.1.1.6 Influence of aspect on regeneration 57 5.1.2 Soil 58 5.1.3 Ecological Vegetation Classes and associated species 59 5.1.4 Climate 61 5.1.5 Effect of Patch Size 61 5.1.6 Land use and competition 62 5.2 Health of the Ballarat Snow Gums 64 5.2.1 General health discoveries 64 5.2.2 Comparison with 1996 project 64 5.2.3 Fruit Crop 64 5.2.4 Flowering 65 5.2.5 Mistletoe 65 5.2.6 Tree form 65 5.2.7 Diameter at Breast Height 66 5.2.8 Land Tenure, grazing and fencing 66 5.2.9 Vegetation community 67 5.2.10 Exotic Species 68 5.2.11 Soil 68 5.2.12 Regeneration 68 6 6. Conclusion – Answers to hypotheses 69 6.1 Distribution of the Ballarat Snow Gums 69 6.2 Health of the Ballarat Snow Gums 70 6.3 Implications for the Ballarat Snow Gum population 71 6.4 Dissemination Pathway 72 7. References 73 8. Appendices 77 Appendix I Study Sites 77 Appendix II Field Data Sheet 79 Appendix III Identification Key 81 Appendix IV Landform Key 82 Appendix V Adjacent Landuse Key 83 Appendix VI Data logger location map 84 Appendix VII Soil group map 85 Appendix VIII Full species list 86 Appendix IX Ecological Vegetation Classes map 90 7 8 1. Introduction The distribution of vegetation in Australia is largely determined by the geological and climatic history of landscapes (Fox 1999). The Snow Gum, Eucalyptus pauciflora, was once a dominant and widespread species in woodlands and forests across a range of altitudes in Victoria (Williams 1991). It is suggested that the distribution of this species became restricted as the climate warmed after the last ice age, forming a number of subspecies including the lowland Snow Gum, E. pauciflora Sieber ex Spreng. ssp. pauciflora Spreng. (Williams 1991). This subspecies generally occurs at lower altitudes than other subspecies, overlapping the range of subsp. niphophila and subsp. acerina (Nicolle 2006). While other subspecies of Eucalyptus pauciflora remain widespread, rapid clearing of these vegetation types for agriculture and urban development in lowland areas has drastically limited the distribution of this subspecies, which is now restricted to small fragmented populations (Williams 1991). Populations occur in southern New South Wales, Tasmania, Victoria, and extending just over the border into South Australia (Brooker and Kleinig 1983). Most of these remnants are highly disturbed, and occur on roadsides or on private land as small patches or isolated paddock trees, where relatively few are protected from the impacts of grazing, cropping and altered nutrient regimes (Baker 1996). In addition, the prolonged drought in the study area has further stressed this vegetation, reducing their ability to cope with these anthropological impacts. This leads to the decline of these patches through clearing, dieback and gradual senescence of mature trees, and without recruitment of seedlings, will gradually disappear (Gibbons and Boak 2002). Eucalyptus pauciflora ssp. pauciflora, of the Myrtaceae family, derives its name from the Latin words “pauci” meaning “few” and “florus” meaning “flowered” and is also referred to as White Sallee in published literature (Costermans 1994). The name, “few flowers” is quite misleading as E. pauciflora flowers profusely from October to January and was the result of a poorly representative sample being collected and named by Franz Sieber in 1823 (Maurice 2003). E. pauciflora is a slow growing and long lived species with large fruits and very distinct glossy, thick and waxy leaves with parallel veins (Maurice 2003). Little is presently known about the limiting factors associated with the health and distribution of E. pauciflora ssp. pauciflora. The 1996 study by Baker provided some insight into these factors in the Ballarat region, indicating a tendency for this species to inhabit ecotones (the transition zone between two ecotypes).