Lincoln University Digital Thesis Copyright Statement The digital copy of this thesis is protected by the Copyright Act 1994 (New Zealand). This thesis may be consulted by you, provided you comply with the provisions of the Act and the following conditions of use: you will use the copy only for the purposes of research or private study you will recognise the author's right to be identified as the author of the thesis and due acknowledgement will be made to the author where appropriate you will obtain the author's permission before publishing any material from the thesis. The Interaction of New Zealand Native Plants with Nitrogen in Canterbury’s Agricultural Landscapes A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University by Hannah Mayford Franklin Lincoln University 2014 Abstract of a thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy. Abstract The Interaction of New Zealand Native Plants with Nitrogen in Canterbury’s Agricultural Landscapes by Hannah Mayford Franklin Less than 0.5 % native vegetation cover remains in the productive Canterbury Plains region of New Zealand. Incorporating native plants into agricultural landscapes could provide numerous benefits including shelter, supplementary stock fodder, production of essential oils or honey, wildlife-corridors, and protection of waterways. New Zealand’s native species are adapted to environments where nitrogen (N) occurs at low concentrations. Such environments are in stark contrast to New Zealand’s agricultural landscapes, where high inputs of fertilisers and animal effluents have elevated soil N. There is a lack of knowledge on how native species will interact with N in agricultural environments. Potentially, native species may alter nitrate leaching to receiving waters and emissions of nitrous oxide (N2O), a potent greenhouse gas. This research aims to investigate the interaction with soil N of selected native species and their rhizospheres to gain an understanding of species-specific differences and potential effects on N fluxes. The native species investigated were typical of those used in restoration projects. Perennial ryegrass (Lolium perenne), an introduced species that dominates New Zealand pasturelands, was used as a control. I studied rhizosphere soil and foliar N status at two planted restoration sites. Plant growth and uptake in response to agriculturally elevated N levels were investigated in greenhouse pot trials. A field experiment explored the effect of Kunzea robusta (kānuka) on N2O fluxes from soil. Finally, farm-scale N uptake and reduction in N losses were modelled for various native planting scenarios. At the restoration sites New Zealand native species Austroderia richardii (toetoe), Phormium tenax (flax), Cordyline australis (cabbage tree), Coprosma robusta (karamu), K. robusta, Olearia paniculata (akeake) and Pittosporum tenuifolium (black matipo) had similar foliar N concentrations to L. perenne. While native species with winter leaf loss, Plagianthus regius (ribbonwood) and Sophora i microphylla (kōwhai), had higher foliar N than these other species. There was significant inter-species variation in rhizosphere soil mineral N concentrations among native species, with A. richardii and P. regius having higher nitrate status than L. perenne. Pot trials revealed that while native species tolerate high N-loading (up to 1600 kg ha-1), there was negligible growth response. Increased soil N concentrations resulted in increased foliar N in native plants, of which the high-biomass-producing monocotyledons assimilated the most. Nevertheless, foliar N concentrations were higher for L. perenne receiving N and farm-scale calculations showed L. perenne to extract more soil N than the native species. K. robusta reduced N2O emissions following effluent application by 80 % relative to control soil, which emitted significant amounts. Modelling revealed that incorporating native species into agricultural landscapes reduced the N loading per hectare due to the reduced area of fertilised and grazed soil. The native monocotyledons, in particular P. tenax and Carex virgata (pukio), have greater potential to reduce nitrate leaching than the woody species and are the most suitable for receiving effluent, whereas K. robusta in farm paddocks may mitigate N2O emissions following urine deposition by sheltering stock. Further work could involve lysimetry to quantify simultaneously the effects of native species on nitrate leaching and N2O emissions. These findings provide a first step towards targeted native planting strategies in sustainable agricultural management. Keywords: New Zealand native plant species, rhizosphere, vegetation loss, nitrogen, nitrate leaching, nitrous oxide, agriculture, Lolium perenne, nutrient uptake, dairy farming ii Acknowledgements Firstly, I would like to express my sincere thanks to my supervisors Professor Nicholas Dickinson and Associate Professor Brett Robinson for their continual support, encouragement and guidance thought my PhD research. Thank you for all your reading and helpful comments during the writing process. You were both a big part of my decision to begin my PhD and it has been my pleasure to work with you both. The technicians in the Soil and Physical Sciences Department at Lincoln University have provided outstanding service in their assistance with laboratory equipment and the timely analysis of samples. I would particularly like to thank Roger Cresswell, Roger McLenaghen, Qian Liang, Manjula Premaratne, Vicky Zhang, Lynne Clucas, Roger Atkinson, Leanne Hassall, Roger Atkinson and Trevor Hendry. I am also indebted to the staff at the Lincoln University Nursery Greenhouse Complex, Brent Richards and Leona Meachen, without whom extensive glasshouse trials would not have been possible. Thank you also to Amal Torky, Emma Gambles, Chrissy Gibson, Gail Harkers and Robyn Wilson for administrative assistance and making my time at Lincoln University so easy. I am grateful for the advice of Professor Leo Condron at the outset of this project. I would like to thank Carol Smith for her assistance with soil profile descriptions, as well as Jim Moir, Nimlesh Balaine and Professor Timothy Clough for their advice when setting up experiments. It was a pleasure to work with Cyril Enault from Agrocampus-Ouest in France during his internship placement at Lincoln University and Roshean Woods during her time as an honours student. I greatly appreciate your contributions to Chapter 5 and 6 respectively, as well as your company and enthusiasm during experimental work. I also wish to acknowledge staff and students within the department who have willingly assisted me with field, glasshouse and laboratory work and whose company has made my thesis time so enjoyable. A special thanks to Youngnam Kim, Tao Zhong, Paula Greer, Juergen Esperschuetz and Obed Nedjo Lense for working long hours in the greenhouse helping me harvest experimental plants and for so much digging in the field. I am also grateful for the help of Jason Hahner, Quam-are Kim, Dharini Paramashivam and Rebecca Dollery. Without you, the PhD would have been impossible. iii I was lucky to receive many scholarships during my PhD. Thank you to the Lincoln University Doctoral Scholarship 2012, Gordon Williams Postgraduate Scholarship in Ecology 2012 and William Gao Postgraduate Scholarship for Excellence 2014 for stipend assistance. In addition, the New Zealand Federation of Graduate Women Canterbury Branch Conference Presentation Travel Award 2013 and the Claude McCarthy Fellowship for assistance with conference travel. I am thankful to have received research funding from Lincoln University and generous contributions from Pioneer Brand Products (Genetic Technologies Ltd) and South Island Dairy Event. To my most amazing proof-readers, Sarah Dawson and Anna Henderson, yet again I cannot express how grateful I am for your help and for finding all the errors that I never see. A final thanks is needed to my family, partner, flatmates and friends for their support, encouragement and keeping me sane during the past three years. iv New Zealand native species in a planted area at the Lincoln University Dairy Farm. v Table of Contents Abstract ........................................................................................................................................ i Acknowledgements ..................................................................................................................... iii Table of Contents ........................................................................................................................ vi List of Tables ............................................................................................................................... ix List of Figures ............................................................................................................................... x List of Plates ............................................................................................................................... xii List of plant species and glossary of abbreviations ...................................................................... xiii Chapter 1 Introduction .......................................................................................................... 1 1.1 General Introduction...................................................................................................................... 1