Ecology and Management of Non-Native Poa Annua on Sub-Antarctic Macquarie Island

Ecology and management of non-native Poa annua on sub-Antarctic Macquarie Island

A dissertation submitted by Laura Kate Williams BSc Honours (University of Adelaide)

A thesis submitted for the degree of Doctor of Philosophy At the University of New England May, 2016

DECLARATION I certify that the substance of this thesis has not already been submitted for any degree and is not currently being submitted for any other degree or qualification. I certify that any help received in preparing this thesis and all sources have been acknowledged in this thesis.

Laura Kate Williams

STATEMENT OF THE CONTRIBUTION OF OTHERS Financial Support

• Australian Postgraduate Award, University of New England • University of New England Completion Scholarship • Australian Antarctic Division, Project no. AAS 4158 • School of Environmental and Rural Science, University of New England • NSW Weed Society (travel support) • Council of Australasian Weed Societies (travel support) In-Kind Support

• Australian Antarctic Division • School of Environmental and Rural Science, University of New England • Tasmanian Parks and Wildlife Service Data Collection and Field Assistance

• Prof. Brian Sindel, University of New England • Dr Susan Wilson, University of New England • Dr Luis Rodriguez Pertierra • Macquarie Island expeditioners Experimental and Laboratory Support

• Dr. Robert Smilie, University of New England • Kirsten Drew, University of New England • Ewan Patterson, University of New England • Leanne Lisle, University of New England • Michael Faint, University of New England • Gary Cluley, University of New England • Andrew Wallace, University of New England • Dr Susan Wilson, University of New England • Dr Justine Shaw, Australian Antarctic Division/University of Queensland Statistical and Analytical Support

• Dr, Paul Kristiansen, University of New England

• Prof. Brian Sindel, University of New England • Dr. Susan Wilson, University of New England • Dr. Justine Shaw, Australian Antarctic Division/University of Queensland Supervision and Editorial Support

• Dr, Paul Kristiansen, University of New England • Prof. Brian Sindel, University of New England • Dr. Susan Wilson, University of New England • Dr. Justine Shaw, Australian Antarctic Division/University of Queensland • Dr. Dana Bergstrom, Australian Antarctic Division • Dr. Alex Terauds, Australian Antarctic Division

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ACCESS AND PERMITS Access to Macquarie Island and authority to operate within the Macquarie Island Nature Reserve was granted by the Tasmanian Parks and Wildlife Service. Field experimental set-up, sampling and sample collection for this thesis was conducted under Tasmanian Department of Primary Industries, Parks, Water and the Environment permit numbers ES 12274, FL 12273 (2013), ES 13204, FL 13206 (2013/2014), ES 13204 and FL 14362 (2015). All samples were transported, stored and analysed in bio-secure conditions at the University of New England, Armidale, NSW and Australian Antarctic Division, Kingston, TAS and destroyed after use.

PUBLICATIONS ARISING FROM THIS THESIS Williams, L., Kristiansen, P., Shaw, J., Sindel, B., & Wilson, S.C. (2013) Weeds down under: Invasion of the sub-Antarctic wilderness of Macquarie Island. Plant Protection Quarterly, 28 (3), 71-72 (see Appendix 1). Williams, L. K., Howard, C., & Scott, J. (in review) Change in the distribution of the indigenous grass Poa litorosa on sub-Antarctic Macquarie Island following the eradication of rabbits. Papers and Proceedings of the Royal Society of Tasmania (sideline project to PhD). Williams, L. K., Kristiansen, P., Sindel, B.M., Wilson, S.C., & Shaw, J. (published online 4th May 2016) Quantifying the seed bank of an invasive grass in the sub-Antarctic: seed density, depth, persistence and viability. Biological Invasions, 1-14 . DOI 10.1007/s10530-016-1154-x (see Appendix 2).

CONFERENCE PRESENTATIONS Williams, L., Kristiansen, P., Shaw, J., Sindel B., & Wilson, S.C. (2013) Weeds down under: Invasion of the sub-Antarctic wilderness of Macquarie Island. 17 th NSW Weeds Conference , Corowa. Williams, L., Kristiansen, P., Shaw, J., Sindel B., & Wilson, S.C. (2013) Ecology and management of invasive Poa annua in the sub-Antarctic. Strategic Science in Antarctica , Hobart. Williams, L., Kristiansen, P., Shaw, J., Sindel B., & Wilson, S.C. (2014) Management techniques for Poa annua in the sub-Antarctic. XXXIII SCAR Open Science Conference , Auckland. Williams, L.K., Kristiansen, P., Sindel, B.M., Shaw, J.D., Wilson, S.C. (2014) Management of invasive Poa annua in the sub-Antarctic wilderness of Macquarie Island. 19 th Australasian Weeds Conference , Hobart. Williams, L.K., Kristiansen, P., Sindel, B.M., Wilson, S.C., & Shaw, J.D. (2015) Management of an invasive grass in the sub-Antarctic: herbicide efficacy and selectivity. 13 th International Conference of Ecology and Management of Alien Plant Invasions , Hawaii Island. Williams, L.K., Kristiansen, P., Sindel, B.M., Shaw, J.D., Wilson, S.C. (2015) Herbicides show potential in effectively and selectively controlling non-native Poa annua under sub-Antarctic temperatures. Australian Turf grass Conference, Hunter Valley.

ACKNOWLEDGEMENTS I am thankful to my four supervisors, for their support and guidance. Paul Kristiansen for leading the project, never ending admin, and helping me to (somewhat) master R, Susan Wilson for valuable chemistry experience and input, Brian Sindel for sharing an amazing adventure to Antarctica, meticulous reviews, and always looking out for me; and to Justine Shaw for invaluable knowledge of the sub-Antarctic, finding solutions to problems I thought insurmountable, pushing me to strive for the best and being a wonderful role model for women in science. The staff in Agronomy welcomed me and provided invaluable support, in particular Mick Faint, Gary Cluley, Leanne Lisle, Roz Mortimer and Greg Chamberlain. Ewan Patterson, Kirsten Drew, Bob Smilie and Andrew Wallace were integral in the chemistry component. Many people at the Australian Antarctic Division provided advice and supervisory and logistical support and got me to Macquarie Island three times despite the odds! The Orion took us back when we missed out the first time. The Macca expeditioners contributed to the experience of a lifetime and lugged many heavy soil cores across the plateau - a big ask! Thanks to Luis Rodriguez Pertierra and Brian Sindel for an entire season of field support and the female sub-Antarctic botanists who provided me boundless support and knowledge and are inspiring role models - Justine Shaw, Jennie Whinam, Dana Bergstrom and Jenny Scott. Thanks to my friends in Armidale and Hobart, especially the girls at the AAD for continual support, lunch time discussions and chocolate deliveries, I hope I can do the same for you! Most of all I my family, I couldn’t have done it without you. Particularly Mum who was always at the end of the phone with a solution, Dad who always had a story to take my mind off things and both of you for helping me to pursue my dreams and instilling in me a love for the environment - it all started when I named our dog after that pretty little white flower…..

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PREFACE This thesis has been prepared for submission by publication. I have attempted to minimize repetition between the chapters, however some remains particularly in the methodology sections. This is due to the requirements of the journals, as well as the need for the papers to stand alone.

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GLOSSERY OF TERMS Alien species: With respect to a particular ecosystem, any species including its seeds, eggs, spores or other biological material capable of propagating that species, that is not native to that ecosystem (Monaco et al. 2002) Invasive species: A species (usually alien) whose introduction leads to further spread and may cause economic or environmental harm or harm to human health (Monaco et al. 2002) Native species: With respect to a particular ecosystem, a species that, other than as a result of an introduction, historically occurred/currently occurs in that ecosystem (Monaco et al. 2002) Southern Cool Temperate/Ocean Temperate Islands: Islands north of the Antarctic Polar Frontal Zone including the Falklands, New Zealand Shelf Islands and the islands and archipelagos of Tristan de Cahuna, Gough, St Paul and Amsterdam which have woody vegetation and a milder climate (Convey 2007) Southern Ocean Islands: The islands of the sub-Antarctic together with the Cool Temperate Islands, between 37-60 °S (Convey 2007) Sub-Antarctic islands: Islands forming a ring around the Antarctic Polar Frontal Zone between 46-54 °S, including Crozet, Kerguelen, Macquarie, Marion, McDonald, Prince Edwards group and South Georgia, where trees and shrubs are absent (Convey 2007) Weed: A plant growing where it is undesired, or out of place (Monaco et al. 2002)

TABLE OF CONTENTS

DECLARATION...... i STATEMENT OF THE CONTRIBUTION OF OTHERS ...... ii ACCESS AND PERMITS ...... iv PUBLICATIONS ARISING FROM THIS THESIS ...... v CONFERENCE PRESENTATIONS ...... vi ACKNOWLEDGEMENTS ...... vii PREFACE ...... viii GLOSSERY OF TERMS ...... ix TABLE OF CONTENTS ...... x LIST OF FIGURES ...... xii LIST OF TABLES ...... xiv ABSTRACT ...... 1 Chapter 1 General Introduction ...... 3 General introduction ...... 4 Poa annua ...... 12 Control of invasive species ...... 16 Implications ...... 19 Chapter 2 Longevity, growth and community ecology of invasive Poa annua across environmental gradients on sub-Antarctic Macquarie Island...... 23 Abstract ...... 24 Introduction ...... 24 Chapter 3 Quantifying the seed bank of an invasive grass in the sub-Antarctic: seed density, depth, persistence and viability ...... 42 Abstract ...... 43 Chapter 4 Efficacy and impact of invasive grass management in a protected area: Poa annua in the sub-Antarctic ...... 63 Summary ...... 64 Introduction ...... 64 Methods ...... 67 Results ...... 72

Discussion ...... 81 Conclusions and recommendations ...... 83 Chapter 5 Leaching of glyphosate and AMPA in two sub-Antarctic soils and potential ecosystem impacts of glyphosate application on Macquarie Island ...... 85 Abstract ...... 86 Introduction ...... 87 Methods ...... 90 Results ...... 95 Discussion ...... 102 Chapter 6 General discussion ...... 113 General discussion ...... 114 Implications for the management of Poa annua in the sub-Antarctic ...... 117 Recommendations for future work ...... 118 Conclusions ...... 119 Chapter 7 References ...... 121 Appendices ...... 142 Appendix 1 – Publication arising from chapter 2 ...... 142 Appendix 2 Paper arising from Chapter 4 ...... 144 Appendix 3 Assessment of the efficacy of various methods for the control of Poa annua presented in the literature ...... 158 Appendix 4 Studies on the toxicity of biota relevant to Macquarie Island ...... 169

LIST OF FIGURES

Figure 1.1 (Top) Southern Ocean Islands, including the sub-Antarctic islands ringed in red (Australian Antarctic Data Centre 2011); (bottom) Macquarie Island showing the location of the station and field huts 5 Figure 1.2 Biogeographical features on Macquarie Island. (Left-right): Isthmus and North Head at the northern end of the island; the plateau; east coast of the island; feldmark 8 Figure 1.3 Major vegetation communities on Macquarie Island. (Left-right): tall tussock grassland; short grassland; herbfield; mire; feldmark; fernbrake 9 Figure 2.1 Inset: location of Macquarie Island in the Southern Ocean (Australian Antarctic Data Centre 2005); and location of study sites on Macquarie Island. Sites were either at low elevation (< 50 m above sea level) with high Poa annua cover (> 60 %) ( ò), mid altitude (100-150 m) with medium P. annua cover (15-50 %) ( ¢) or at high altitude (> 250 m) with low P. annua cover (< 10 %) ( ▲), filled symbols are sites established in 2013, unfilled symbols are sites established in 2014 29 Figure 2.2 Number of tagged Poa annua plants remaining at Tractor Rock ( ); Bauer Bay Beach ( ); Bauer Bay Slope ( r); Doctor’s Track ( ); Lower Boot Hill (×) and Upper Boot Hill (+) after 0 (February 2013), 11 (December 2013), 14 (March 2014) and 27 (April 2015) months 33 Figure 2.3 Principal component analysis of Poa annua cover Poa; plant morphological traits: Dry weight Wei; number of tillers Til; Tiller length Til.l; Number of reproductive tillers R.til; Root length R.len; and environmental characteristics: Animal disturbance Dis; Elevation Ele; Soil magnesium Mag; Slope Slo; Soil depth S.Dep; Soil pH pH; Soil sand content San; and Water content Whc, according to the first two components. Study sites: Bauer Bay Beach (); Bauer Bay Slope ( r); Doctor’s Track ( ); Lower Boot Hill (×); Tractor Rock ( ) and Upper Boot Hill (+) 36 Figure 2.4 Principal component analysis of Poa annua cover Poa, community indices: species richness Ric; Simpson’s diversity SiD; and various environmental characteristics: Animal disturbance Dis; Elevation Ele; Exposure Exp; Potassium Pot; Sulphur Sul; Water content Whc, according to the first two components. Study sites: Bauer Bay Beach ( ); Bauer Bay Slope ( r); Doctor’s Track ( ); Lower Boot Hill (×); Mt Power ( ●); The Nuggets (▲); Sawyer Creek ( ■); Tractor Rock ( ) and Upper Boot Hill (+) 38 Figure 3.1 Inset: location of Macquarie Island in the Southern Ocean (Australian Antarctic Data Centre 2005); and location of seed bank study sites on Macquarie Island 47 Figure 3.2 Study sites on Macquarie Island: a Tractor Rock; b Bauer Bay Beach; c Doctor’s Track; d Bauer Bay Slope; e Lower Boot Hill; f Upper Boot Hill 49 Figure 3.3 Non-linear regression (Mitscherlich function) of Poa annua seed bank density and P. annua cover. Fitted curve ± one (dark grey) and two (light grey) standard errors shown with raw data (filled circles) 55 Figure 4.1 Physical disturbance sites on Macquarie Island were located at low elevation with high Poa annua cover (circles), mid altitude with medium P. annua cover (squares) or at high altitude with low P. annua cover (triangles). Sites established for 16 months are shown by open symbols, sites established for 27 months are shown by closed symbols. Inset: location of Macquarie Island in the Southern Ocean (Australian Antarctic Data Centre 2005) 69

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Figure 4.2 Poa annua cover 0 (February 2013), 11 (December 2013), 14 (March 2014) and 27 (April 2015) months after treatment at Bauer Bay Beach ( ), Bauer Bay Slope ( ), Doctor’s Track (+) and Tractor Rock ( ), error bars represent 95 % confidence intervals 73 Figure 4.3 Poa annua cover 0 (December 2013), 3 (March 2014) and 16 (April 2015) months after treatment at The Nuggets (+),Sawyer Creek ( ), Lower Boot Hill ( ), Upper Boot Hill ( ) and Mount Power ( ), error bars represent 95 % confidence intervals 74 Figure 4.4 Mean injury rating of Poa annua 12 weeks after the application of herbicides, where an injury rating of 1 indicates no effects to the plant and an injury rating of 9 indicates plant death ± 95 % confidence intervals. Filled bars indicate a significant effect of the herbicide ( P < 0.05) 75 Figure 4.5 Mean injury rating of Poa annua plants 10 weeks after the application of herbicides using a brush (light grey bars) or spray (dark grey bars) application method, where an injury rating of 1 indicates no effects to the plant and an injury rating of 9 indicates plant death. Error bars represent 95 % confidence intervals 77 Figure 4.6 Injury rating of Poa annua (dark grey bars) and 3 native grass species Agrostis magellanica (unfilled bars), Festuca contracta (light grey bars) and Poa foliosa (mid grey bars) at 0.25, 0.5, 1 and 2 times the recommended herbicide application rate, 10 weeks after application. Error bars represent 95 % confidence intervals 81 Figure 5.1 Molecular structure of glyphosate and aminomethylphosphonic acid 88 Figure 5.2 The columns for the leaching experiment consisted of 20 cm of plastic tubing containing soil (a) capped with glass wool (b), two pieces of filer paper (c) and a plastic cap with leaching holes (d) 92 Figure 5.3 Columns used in the leaching experiment (left) and layout of columns in the cool room beneath lights (12 hours light/12 hours dark) (right) 92 Figure 5.4 Mean concentration of glyphosate in the leachate of treated sand cores and peat cores over 48 weeks (data presented as mean ± standard deviation, raw data is plotted in grey) 99 Figure 5.5 Total mean amount of glyphosate leached from the sand cores and peat cores over 48 weeks (data presented as mean ± standard deviation, raw data is plotted in grey) 99 Figure 5.6 Mean concentration of aminomethylphosphonic acid (AMPA) in the leachate of treated sand cores and peat cores over 48 weeks (data presented as mean ± standard deviation, raw data is plotted in grey) 100 Figure 5.7 Total mean amount of aminomethylphosphonic acid (AMPA) leached from the sand cores and peat cores over 48 weeks (data presented as mean ± standard deviation, raw data is plotted in grey) 100 Figure 5.8 Mean concentrations of bromide in the leachate of treated sand cores and peat cores (data presented as mean ± standard deviation, raw data is plotted in grey) 101 Figure 5.9 Potential fate processes, exposure pathways (indicated by red arrows) and receptors (indicated by red circles) of glyphosate in the Macquarie Island environment 111

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LIST OF TABLES

Table 1.1 Vegetation communities on Macquarie Island 9 Table 2.1 Environmental and soil characteristics of study sites on Macquarie Island, DL = detection limit 32 Table 2.2 Morphological characteristics (mean ± standard deviation/plant) of plants at study sites, significant differences ( P < 0.05) are between sites and shown by different letters, * Antarctica morphology data from Galera et al. (2015) 35 Table 2.3 Mean diversity indices (m -2 ± standard deviation) for each site 35 Table 3.1 Environmental characteristics of seed bank study sites on Macquarie Island 48 Table 3.2 Seed density, persistence (total seed remaining), viability (viable seed remaining) and cover of Poa annua at sites on Macquarie Island. Means ± standard deviation 53 Table 3.3 Bivariate linear regression of seed bank density and various environmental variables 54 Table 4.1 Concentrations of herbicides applied at the recommended label rate in the herbicide screening experiment 70 Table 4.2 Symptoms induced by herbicides on Poa annua and native grass species. B = bleaching; C = chlorosis; N = necrosis; W = wilting 75 Table 4.3 P values of significant differences of various parameters between control plants and plants treated with each herbicide. Significant P values are shown in italics and blank cells indicate a non-significant value. Ami = amitrole, Cle = clethodim, Dit = dithiopyr, Eth = ethofumesate, Flu = flupropanate-sodium, Gly = glyphosate, Ima = imazamox, Met = methabenzthiazuron, Rim = rimsulfuron, Sim = simazine, Tri = trifloxysulfuron sodium 76 Table 4.4 Mean species richness prior to treatment and after 16 months at 1 Year Sites and after 27 months at 2 year sites ± standard error 79 Table 5.1 Characterisation and metal content of a sand and peat soil from Macquarie Island, mean ± standard deviation (all analyses on triplicate subsamples unless otherwise indicated: + 1 sample, * 2 samples) 97

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ABSTRACT Invasive species pose one of the greatest threats to the Antarctic region and consequently control is a priority to managers. To date, all successful eradications of vascular plants in the sub-Antarctic and Antarctica have been on small, restricted populations. Eradication or control is more difficult for widespread species, largely due to established seed banks. Information on the biology of the target species and the efficacy of control can increase eradication success. It is also important to assess the impact of control on non-target species. One widespread invasive species in the Antarctic and sub-Antarctic under consideration for control is the grass Poa annua . For any potential eradication or control programs to be successful, information is required on the species’ ecology and response to control. Therefore with the aim of informing future management of P. annua, my thesis focused on quantifying the ecology of P. annua on Macquarie Island and assessing the efficacy of physical and chemical control. This included assessing the impact of control on native plant species, and the mobility of glyphosate in Macquarie Island soils and potential off-target impacts. I found that P. annua plants showed a perennial lifecycle, a common survival mechanism for sub-Antarctic plants, and they displayed considerable variation in growth forms across environmental gradients. Poa annua plant size and seed banks varied across Macquarie Island in response to P. annua cover and environmental variables. Larger plants and denser seed banks were found at low elevation sites with high P. annua cover, high animal disturbance and deep, sandy soils. The high cover of P. annua at these sites also suppressed native species diversity. Conversely, at high altitude, exposed sites with low P. annua cover and shallow soils, P. annua plants were small and seed bank densities were low or non- existent. Less than 3 % of buried seed remained viable for two years. Plants from all sites allocated most of their biomass to root material (60-80 %), likely to enhance persistence. Physical control methods (scalping, hoeing, trimming, hand weeding) were ineffective on P. annua when applied once. Amitrole, clethodim, glyphosate, rimsulfuron and trifloxysulfuron sodium were all effective on P. annua. However glyphosate at 0.25 times the recommended application rate was the only treatment to also be selective. An integrated control program utilizing low rates of glyphosate to prevent further seed set followed by hand weeding of emerging seedlings is likely to be the most effective. Glyphosate leaching from two Macquarie Island soils was low, less than 2.5 µg L -1 from sand and 5 µg L -1 from peat over 48 weeks in a column leaching trial. This equated to around

0.4 % of the glyphosate applied, with the rest strongly adsorbed to soil. Concentrations in leachates were well below regulatory guidelines and unlikely to impact on Macquarie Island biota, although further research is required, especially on aquatic flora and fauna. My research provides a rare example of assessing the biology of an invasive species and the efficacy and impacts of a range of control methods. It shows that even within the Macquarie Island population, P. annua is highly variable in its seed production, growth habit and size and impact on native plant species. This variability may make management more difficult, however this knowledge into the species’ ecology will be enable management of the species to be more efficient and effective throughout the sub-Antarctic. My research suggests that physical control methods are unlikely to be effective on this species at most locations, and that low rates of glyphosate show potential for effective, selective control, possibly in combination with hand weeding of low density sites. This research will assist managers to develop effective control programs for P. annua in the sub-Antarctic, but will also increase understanding of how invasive species perform in the sub-Antarctic and how information on the ecology of invasive species, and efficacy and impact of control can be used to inform management of invasive species throughout natural areas.