PROCESSES EXPLAINING EXOTIC PLANT OCCURRENCE IN AUSTRALIAN MOUNTAIN SYSTEMS by Mellesa Schroder B.App.Sc. Submitted in fulfillment of the requirements for the degree of Master of Philosophy School of Environmental Science Charles Sturt University Albury February 2014 TABLE OF CONTENTS Figures .............................................................................................................................................. v Tables .............................................................................................................................................. vii Certificate of Authorship ................................................................................................................. ix ACKNOWLEDGMENTS ...................................................................................................................... x ABSTRACT ........................................................................................................................................ xi Chapter 1 Introduction .............................................................................................................. 1 1.1 General introduction......................................................................................................... 1 1.2 Definition of an exotic plant species ................................................................................. 2 1.3 Definition of elevation versus altitude ............................................................................. 3 1.4 Definition of disturbed and undisturbed habitats ............................................................ 3 1.5 Background and study area .............................................................................................. 4 1.6 Land-use history ................................................................................................................ 6 1.7 Why undertake this study? ............................................................................................... 7 1.8 Study aims ......................................................................................................................... 8 1.9 Thesis outline and research questions ............................................................................. 9 Chapter 2 Literature Review .................................................................................................... 11 2.1 Introduction .................................................................................................................... 11 2.2 Exotic plant species literature from global mountainous regions .................................. 11 2.3 Existing exotic plant species research undertaken in the Australian Alps ..................... 14 2.4 The role of disturbance and changes to soil physical and chemical properties in explaining exotic plant species richness and cover ................................................................... 17 2.5 Exotic species trait studies and their relevance to mountain systems .......................... 19 2.6 Synthesis ......................................................................................................................... 19 i Chapter 3 The role of elevation and soil attributes in explaining exotic plant richness in disturbed mountain systems ......................................................................................................... 21 3.1 Introduction .................................................................................................................... 21 3.1.1 Exotic plants in the Australian Alps ............................................................................. 22 3.2 Chapter aims ................................................................................................................... 27 3.3 Study area ....................................................................................................................... 28 3.4 Methods .......................................................................................................................... 28 3.5 Statistical analysis ........................................................................................................... 31 3.6 Results ............................................................................................................................. 33 3.6.1 Exotic species richness between disturbance types ............................................... 33 3.6.2 Elevation and soil attributes .................................................................................... 37 3.7 Discussion ....................................................................................................................... 41 3.8 Conclusion ....................................................................................................................... 46 Chapter 4 The role of elevation and soil attributes in explaining exotic plant richness in undisturbed mountain systems ..................................................................................................... 48 4.1 Introduction .................................................................................................................... 48 4.1.1 Exotic plants in natural areas of the Australian Alps ............................................... 49 4.1.2 Exotic plant occurrence and richness in roadsides and human nodes ................... 51 4.2 Chapter aims ................................................................................................................... 53 4.3 Study area ....................................................................................................................... 54 4.4 Methods .......................................................................................................................... 55 4.5 Statistical analysis ........................................................................................................... 55 4.6 Results ............................................................................................................................. 56 4.6.1 Exotic species richness in undisturbed areas .......................................................... 56 ii 4.6.2 A comparison in exotic species richness between disturbed and undisturbed areas 57 4.6.3 Change in species along an elevation gradient ....................................................... 57 4.6.4 Additional results ..................................................................................................... 61 4.7 Discussion ....................................................................................................................... 62 4.8 Conclusion ....................................................................................................................... 66 Chapter 5 Are abiotic and biotic attributes associated with differences in exotic species composition in disturbed and undisturbed mountain systems? .................................................. 67 5.1 Introduction .................................................................................................................... 67 5.1.1 Exotic plants in the Australian Alps ......................................................................... 69 5.2 Chapter aims ................................................................................................................... 70 5.3 Study area and field methods ......................................................................................... 71 5.4 Statistical analysis ........................................................................................................... 71 5.4.1 Exotic plant composition ......................................................................................... 71 5.4.2 Soil data comparisons .............................................................................................. 72 5.4.3 Relationship of exotic species composition to abiotic factors ................................ 73 5.5 Results ............................................................................................................................. 73 5.5.1 Exotic plant composition ......................................................................................... 73 5.5.2 Soil data comparisons .............................................................................................. 78 5.5.3 Exotic species composition relationship to soil attributes and temperature ......... 79 5.6 Discussion ....................................................................................................................... 84 5.7 Conclusion ....................................................................................................................... 89 Chapter 6 Synthesis and general discussion ............................................................................ 90 6.1 Introduction .................................................................................................................... 90 iii 6.2 The role of elevation and soil attributes in explaining exotic plant richness in disturbed and undisturbed mountain systems .......................................................................................... 90 6.3 The abiotic and biotic attributes associated with differences in exotic species composition in disturbed and undisturbed mountain systems ................................................ 92 6.4 Other considerations in understanding the processes