The effects of shrub removal and grazing on vegetation and soils in a shrub-encroached Australian woodland Stefani Daryanto A thesis in fulfilment of the requirements for the degree of Doctor of Philosophy School of Biological, Earth and Environmental Sciences Faculty of Science February 2013 THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Daryanto First name: Stefani Other name/s: Abbreviation for degree as given in the University calendar: PhD School: School of Biological, Earth and Environmental Faculty: Science Sciences Title: The effects of shrub removal and grazing on vegetation and soils in a shrub-encroached Australian woodland Abstract 350 words maximum: Plant communities and soil properties in many dryland ecosystems have changed dramatically over the past century due to the proliferation of woody plants, caused largely by the introduction of livestock grazing, changes to natural fire regimes, and climate. Areas heavily encroached by shrubs are generally regarded as degraded, and this view is largely based on the fact that shrubs reduce pastoral productivity. There have been many attempts to remove shrubs in pastoral systems using chemical, biological and mechanical techniques to improve pastoral production. It remains unclear, however, whether shrubs per se or the interactions between grazing and climate are responsible for the putative reductions in pastoral productivity in shrub−encroached areas. This thesis examines the long−term ecological effects of mechanical shrub removal by blade−ploughing, with and without grazing, on vegetation and soils in shrub−encroached woodlands in eastern Australia. The results show that the combination of ploughing and grazing creates dramatic effects on soils and vegetation in this dryland system. Chapter 1 provides an overview of shrub encroachment phenomenon, its common association with degradation, as well as the benefits of shrubs and the overall encroachment effects on ecosystem processes. The chapter also describes the results of previous attempts to control shrubs using mechanical removal techniques. Chapters 2 and 3 examine the changes in vegetation and soil disturbances by animals, respectively, that result from mechanical shrub removal. Chapter 4 compares soil properties between ploughed sites occupied by newly−regenerated shrubs and unploughed sites dominated by mature shrubs. Chapters 5 and 6 describe the changes in the spatial distribution of soil nutrients and infiltration of water in a shrubland resulting from different combinations of ploughing and grazing. Chapter 7 examines the role of shrub−encroached lands as sinks for aboveground and belowground carbon (C) and considers the effects of different landscape elements (e.g. shrubs, log or debris mounds, trees) on C storage. Chapter 8, provides a conclusion, and evaluates the potentially negative effects of shrub removal as part of a land management strategy in this semi−arid system and explores the ecosystem values of shrubs including other possibilities to manage shrublands and suggestions for future research. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only) ………………………… ……… ……………………………………..……… ……….………… Signature Witness Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed …… ………………………………………. Date .......12 February 2013………………….............. COPYRIGHT STATEMENT ‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed ……… ……………………………………........................... Date …………22 May 2013…………………………………........................... AUTHENTICITY STATEMENT ‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’ Signed ……… ……………………………………........................... Date ………22 May 2013……………………………………........................... Statement of contributions of co-authors and declarations of permission to publish All publishers and co-authors have granted permission for the following publications to be submitted and published as a thesis. No other authors will be submitting this work as part of their thesis submissions. The contribution of each author to the respective publications is stated below. Chapter 2 Plant and soil surface responses to a combination of shrub removal and grazing in a shrub-encroached woodland Journal of Environmental Management 91 (2010): 2639–2648. DOI: 10.1016/j.jenvman.2010.07.038 Authors: Stefani Daryanto and David J. Eldridge Stefani Daryanto (SD) can claim more than 50% of the work since she undertook all of the field and laboratory work, and 70% of the data analyses that are reported in the paper. She also wrote about 80% of the manuscript. Statistical advice and assistance on the paper was provided by Terry Koen (TBK), a biometrician at the Office of Environment and Heritage, and supervised by Dr David Eldridge (DJE). No other authors will be submitting this work as part of their thesis submissions. This article has been reproduced with kind permission from Journal of Environmental Management and Elsevier. For articles published in Journal of Environmental Management the author retains the right to include the journal article, in full, in a thesis of dissertation. Chapter 3 Shrub hummocks as foci for small animal disturbances in an encroached shrubland Journal of Arid Environments 80 (2012): 35–39. DOI: 10.1016/j.jaridenv.2011.12.001 Authors: Stefani Daryanto and David J. Eldridge SD undertook all of the data analysis, 60% of the field work and wrote 70% of the manuscript. No other authors will be submitting this work as part of their thesis submissions. Advice on statistics was provided by Dr Santiago Soliveres, a post- doctoral fellow working in the Eldridge Lab. The study was conceived by DJE, and supervision was by DJE. This article has been reproduced with kind permission from Journal of Arid Environments and Elsevier. For articles published in Journal of Arid Environments the author retains the right to include the journal article, in full, in a thesis of dissertation. Chapter 4 Soil nutrients under shrub hummocks and debris mounds two decades after ploughing Plant and Soil 351 (2012): 405–419. DOI: 10.1007/s11104-011-0978-5 Authors: Stefani Daryanto , David J. Eldridge, and Terry B. Koen SD undertook more than 75% of the manuscript writing, all of the field and laboratory work. Statistical advice and assistance on the paper was provided by TBK. The study was conceived by DJE, and supervision was by DJE. No other authors will be submitting this work as part of their thesis submissions. Copyright notice: This article was reproduced with kind permission from Springer Science+Business Media: Plant and Soil, Soil nutrients under shrub hummocks and debris mounds two decades after ploughing, 351, 2012, Daryanto, S., Eldridge, D. J., Koen, T. B. (Licence number: 2978620009867). Chapter 5 Ploughing and grazing alter the spatial patterning of surface soils in a shrub-encroached woodland Geoderma 200–201 (2013): 67-76. DOI: 10.1016/j.geoderma.2013.02.006 Authors: Stefani Daryanto, David J. Eldridge, and Lixin Wang SD undertook more than 75% of the manuscript writing, all of the field and laboratory work. Statistical advice and assistance on the paper was provided by Lixin Wang (LW). The study was conceived by DJE and SD, and supervision was by DJE. No other authors will be submitting this work as part of their thesis submissions. Chapter 6 Infiltration of water varies with disturbance in a shrub-encroached woodland Geomorphology in press.