University of Wollongong Thesis Collections University of Wollongong Thesis Collection University of Wollongong Year Indigenous plant recruitment limitation by bitou bush (Chrysanthemoides monilifera spp. rotundata): effect on life history stages and allelopathic mechanisms Emilie-Jane Ens University of Wollongong Ens, Emilie-Jane, Indigenous plant recruitment limitation by bitou bush (Chrysan- themoides monilifera spp. rotundata): effect on life history stages and allelopathic mechanisms, PhD thesis, School of Biological Sciences, University of Wollongong, 2007. http://ro.uow.edu.au/theses/745 This paper is posted at Research Online. http://ro.uow.edu.au/theses/745 Indigenous plant recruitment limitation by bitou bush (Chrysanthemoides monilifera spp. rotundata): effect on life history stages and allelopathic mechanisms A thesis submitted in fulfillment of the requirements for the award of the degree of Doctorate of Philosophy From the School of Biological Sciences University of Wollongong by Emilie-Jane Ens B. Sc. (Hons) 2007 Indigenous coastal vegetation Bitou bush invasion Regenerating bitou bush Content Table of Contents Abstract…………….......................................................................................xi Acknowledgements......................................................................................xvii Chapter 1: General Introduction...................................................................1 1.1 The phenomenon of exotic plant invasion........................................................... 1 1.1.1 Definitions........................................................................................................... 1 1.1.2 History and modes of exotic invasive plant introduction ................................... 1 1.2 Impacts of plant invasion ..................................................................................... 3 1.2.1 Detection and difficulty of impact assessment.................................................... 3 1.2.2 Effects on resident plants .................................................................................... 6 1.2.3 Effects on ecosystem function ............................................................................ 8 1.3 Mechanisms of plant invasion.............................................................................. 9 1.3.1 Exploitation competition................................................................................... 13 Deleted: 17 1.3.2 Interference competition ................................................................................... 18 1.3.3 Occupation of free space................................................................................... 20 1.4 Bitou bush invasion in Australia........................................................................ 21 1.4.1 History of invasion............................................................................................ 21 1.4.2 Biodiversity impacts ......................................................................................... 22 1.4.3 Mechanisms of invasion.................................................................................... 22 1.5 Research aims...................................................................................................... 24 1.6 Thesis outline....................................................................................................... 25 Chapter 2: Exotic woody invader limits the recruitment of three indigenous plant species..............................................................27 2.1 Introduction......................................................................................................... 27 2.2 Methods................................................................................................................ 31 2.2.1 Study location and study species ...................................................................... 31 2.2.2 Population structure.......................................................................................... 33 2.2.3 Morphological and physiological responses..................................................... 33 2.2.4 Statistical analysis............................................................................................. 34 i Content 2.3 Results .................................................................................................................. 35 2.3.1 Population structure.......................................................................................... 35 2.3.2 Morphological and physiological responses of mature indigenous species ..... 37 2.4 Discussion............................................................................................................. 40 Chapter 3: Seasonal photosynthetic patterns of mature Australian coastal plants and physiological tolerance to exotic woody weed invasion. .......................................................................................47 3.1 Introduction......................................................................................................... 47 3.2 Materials and methods ....................................................................................... 50 3.2.1 Study location................................................................................................... 50 3.2.2 Microhabitat physico-chemical characteristics................................................. 51 3.2.3 Seasonal in-situ ΦPSII and Pmax of C. alba, M. elliptica and L. longifolia in invaded and non-invaded habitats..................................................................... 52 3.2.4 Seasonal Fv/Fm of C. alba, M. elliptica and L. longifolia in invaded and non- invaded habitats................................................................................................. 53 3.2.5 Statistical analysis............................................................................................. 53 3.3 Results .................................................................................................................. 54 3.3.1 Climate .............................................................................................................. 54 3.3.2 Microhabitat physico-chemical characteristics................................................. 56 3.3.2 Seasonal in-situ ΦPSII and Pmax of mature C. alba, M. elliptica and L. longifolia ........................................................................................................... 59 3.3.4 Seasonal Fv/fm of C. alba, M. elliptica and L. longifolia in invaded and non- invaded habitats................................................................................................. 60 3.4 Discussion............................................................................................................. 64 Chapter 4: Determination of potential allelopathy and indirect soil chemical interference by an exotic invasive plant using a comprehensive bioassay protocol...............................................68 4.1 Introduction......................................................................................................... 68 4.1.1 Protocol for determination of phytotoxicity, allelopathy and indirect soil effects................................................................................................................ 70 ii Content 4.2 Materials and methods ....................................................................................... 72 4.2.1 Exotic extract species........................................................................................ 72 4.2.2 Bioassay test species ......................................................................................... 74 4.2.3 Extraction procedure ......................................................................................... 74 4.2.4 Extract concentrations....................................................................................... 75 4.2.5 Bioassay procedure........................................................................................... 75 4.2.6 Statistical analysis............................................................................................. 77 4.3 Results .................................................................................................................. 78 4.3.1 Bitou bush and acacia extracts .......................................................................... 78 4.3.2 Effects on germination ...................................................................................... 80 4.3.3 Effects on shoot and root length........................................................................ 82 4.3.5 Phytotoxic, allelopathic and indirect soil effects .............................................. 84 5.4 Discussion............................................................................................................. 85 Chapter 5: Identification of volatile compounds released by roots of an invasive plant, bitou bush (Chrysanthemoides monilifera spp. rotundata), and their potential biological role...........................90 5.1 Introduction......................................................................................................... 90 5.2 Materials and methods ....................................................................................... 95 5.2.1 Root collection and extraction .......................................................................... 95 5.2.2 Soil collection and extraction...........................................................................