Management and restoration of native grassy woodland in the Midlands of ..I Tasmania by ~ob~,k Andrew Zacharek B. Sc., Grad. Dip. Env. Stud. (Hons) f\. Submitted in fulfillment of the requirements of the degree of Doctor of Philosophy Department of Geography and Environmental Studies University of Tasmania Hobart March 1997 i Declaration This thesis contains no material which has been accepted for the award of any other degree or diploma in any tertiary institution and to the best of my knowledge and belief, the thesis contains no material previously published or written by another person, except when due reference is made in the text. Andrew Zacharek ii Abstract This thesis examines the effects of agricultural and conservation management practices on grassy communities in the sub-humid, low altitude Midlands of Tasmania. The results of an extensive survey were examined to assess the effects of grazing by sheep and cattle, fertilisation and the introduction of exotic pasture species on the grassy communities. Sites were classified according to the degree of pasture conversion and the level of the main limiting nutrient phosphorus, by annual rainfall and by geological substrate. Exotic species replaced native species with increasing degrees of pasture conversion and levels of phosphorus. Effects of management varied rainfall and different geological substrates. Raunkiaer life-form groups were a useful aid in the identification of patterns of species' responses. Exotic therophytes and flat/versatile rosette hemicryptophytes were the most invasive exotic life-forms in native communities. The native species in the flat/versatile rosette and caespitose hemicryptophyte life-form groups were the most tolerant of disturbance. The effects of fertilisation alone on native communities were increased agricultural productivity but a reduction in the diversity of native species and the conservation values of the communities. At the Township Lagoon Nature Reserve, three levels of grazing pressure, light in the reserve and moderate and higher levels in adjacent paddocks, were compared. The moderate level of grazing altered species composition but native species diversity declined only under the high grazing regime. A replicated experiment, with a gas flame used to provide heat energy, compared the responses of vegetation to burning. Treatments were single bums at four different times of the year, bums at those times in two consecutive years and a no burning treatment. Phenology varied considerably between species. Burning promoted most species when it occurred a short time before main growing season of that species. In addition, most species were suppressed by burning which occurred during their main growing season or iii before seed dispersal. Burning in two consecutive years tended to increase the seasonal effects. The effects of weeding techniques on species and life-forms in grassland dominated by exotic species were examined over a 10 month period from spring 1991. The weeding techniques were removal of topsoil, herbiciding and burning. The effects varied between species, and depended on the protection of buds from disturbance, the presence of seed for recruitment and the conditions for growth of the species. The levels of dissimilarity between the responses of all pairs of species to disturbance in this study were calculated using the Gower metric index of dissimilarity. The degree of dissimilarity within the life-form groups was less than that between the life-form groups for only a small proportion of comparisons. Species were classified using TWINSPAN into response or functional groups based on their responses to disturbance. Groups were classified mainly by responses to agricultural management, and the responses to grazing level, burning and weed-control techniques were highly variable. The response groups were not associated with the Raunkiaer life-form group to which the species belonged. The responses of species classified into Raunkiaer life-form groups were highly variable. The life-form group was an aid to describing overall responses of species, but would be a poor predictor of the likely response of any one species to management. Active management of grasslands could be used to manipulate their species composition as many species are highly sensitive to the types and levels of disturbance. Conservation management of native grassy communities must be based on the site­ specific responses of individual species to disturbance. iv Acknowledgments This thesis was partly funded by National Estate Grants Program (through the Tasmanian Conservation Trust), and by an Australian Postgraduate Research Award. The Wool Research and Development Corporation funded the pasture survey during which I was employed by the Department of Primary Industry and Fisheries (Tasmania). I am indebted to many people who have helped me throughout the duration of my studies: I thank my supervisor, Prof. Jamie Kirkpatrick for his wonderful support, enthusiasm, tolerance, patience throughout. I would like to thank the steering committee of the pasture survey, landholders and Dr. Doug Friend for organising and allowing my access to the invaluable data from the pasture survey During the period of employment at DPIF, I appreciated the help and company of Doug Friend, Robin Thompson, Peter Ball, Nick Wachsmann. I would like to thank the staff and students of Department of Geography and Environmental Studies for company and support in many ways. Louise Gilfedder, Adrian Pyrke and Mark Chladil provided support and advice. Kerrie Green expertly handled the administration and moneys at Geography and Environmental Studies. Nick Sawyer and Margaret Atkinson handled the administration at the Tasmanian Conservation Trust. Denis Charlesworth carried out chemical analyses of Chapter 4. David Sommerville helped with equipment and transport. Guus van der Geer drew the map of TLNR. Department or Parks, Wildlife and Heritage provided the use of a glasshouse. Jock Waugh gave advice on growing plants and kindly allowing use of shadehouse space at Ross. A number of people helped with fieldwork including Steve Harris, Louise Mendel, Mark Chladil, Andy North, Mike Askey-Doran, Rebecca Cannell, Doug Walsh, the Wellbeing Club and many other volunteers. Wayne and Paul Triffett kindly gave access to their land, and local knowledge. v Mr. Bert Lodge also gave permission to access his land. David Ratkowsky gave valuable statistical advice. Kate Challis ~elped with the literature search and proofreading. Kerry Bridle kindly read and commented on early drafts of the thesis. Mona Loofs expertly proofread final drafts of the thesis. Kate Challis helped with childcare in many ways and has provided great support, company and sympathy. I thank Audrey Zacharek for childcare, support and sympathy. Teshi and Lena Zacharek made sacrifices for this thesis vi Contents DECLARATION ......................................................................................................................................... I ABSTRACT .....................................................................................................................................•.......... ii ACKNOWLEDGMENTS ........................................................................................................................ iv CONTENTS ............................................................................................................................................... vi LIST OF FIGURES ................................................................................................................................... ix LIST OF TABLES ................................................................................................................................... xii CHAPTER 1. INTRODUCTION .............................................................................................................. 1 I. I TASMANIAN LOWLAND GRASSY VEGETATION ..................•........••.......................••.................................... I I .2 ECOLOGICAL PROCESSES IN NATIVE GRASSY VEGETATION .......••.........•.............•.•.................................... I I .3 DISTURBANCE ................•...•..............................................................................•...............•................•..... 2 I .4 COMPETITION ................•...••..•....................•............................•..•....•...............•••..............••...............•••... 3 I .5 COMMUNITY STRUCTURE ....••................•.....••.....•..............•....•.••.•.....................••..•...•.........•.•..................4 I .6 LIFE-FORM GROUPS AND FUNCTIONAL ATTRIBUTES OF SPECIES ......•....•...•................•........•.................... .5 I .7 THE VEGETATION OF THE DRY LOWLAND AREAS OF TASMANIA ....•.•.....••.........•.........•................•............ 7 I .8 AGRICULTURAL MANAGEMENT .......•......•........................................•........................•...............•...............9 I.8.I Cropping and pasture improvement ................................................................................................ 9 I.8.2 Grazing management ....................................................................... : ............................................. IO I .8.3 Effects of grazing .......................................................................................................................... I I 1.8.4 Effects of grazing on communities ..........................•....................................................................