GROWTH AND PHOTOSYNTHETIC RESPONSES OF AUSTRALIAN SUBTROPICAL RAINFOREST SPECIES TO VARIABLE LIGHT ENVIRONMENTS: IMPLICATIONS FOR RESTORATION AND MIXED-SPECIES PLANTATIONS By JEFFREY W. KELLY A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2006 Copyright 2006 by Jeffrey W. Kelly To Harrison Shaw Kelly, Harry Erik Grass, and Everett Ruess ACKNOWLEDGMENTS I would like to thank my advisor and committee chair, Dr. Shibu Jose, for his numerous ideas and financial support throughout my research. I would like to express my gratitude to my committee members Dr. Debbie Miller, Dr. Rick Williams, and Dr. Doland Nichols for their gracious assistance and valuable insight. I would also like to thank Peter Bligh-Jones for invaluable assistance during my time in Australia, and thanks go out to Mila Bristow for setting the experiment on the right track. I would like to sincerely thank my parents for their constant benevolence and support during my academic career. I am forever indebted to you both for showing me the wonders of the natural world. I wish to thank Erin Maehr for being such a joy-bringer and wonderful presence in my life. I would also like to thank my good friends from Gainesville, Eric Holzmueller, Robin Collins, and Ped Daneshgar, for providing frequent and well needed non-academic pursuits, to counteract the occasional academic malaise. Finally, I would like to thank some wonderful friends from SLC, Brad Larsen, Jake MacFarlane and Joe and Janica Hayes, for proving that true friendship can survive great distances and tumultuous events. iv TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................................................................................. iv LIST OF TABLES............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii ABSTRACT....................................................................................................................... ix CHAPTER 1 INTRODUCTION ........................................................................................................1 Ecophysiology ..............................................................................................................2 Physiological Response to Light ..................................................................................3 Leaf Level..............................................................................................................3 Whole Plant Level .................................................................................................5 Successional Gradient...................................................................................................6 History of Australian Rainforest...................................................................................9 History of Subtropical Rainforest in New South Wales.............................................10 Rainforest Characteristics....................................................................................12 Study Species.......................................................................................................13 Objectives and Hypotheses.........................................................................................14 Objective 1...........................................................................................................15 Objective 2...........................................................................................................15 2 GROWTH AND PHOTOSYNTHETIC RESPONSES OF SIX AUSTRALIAN SUBTROPICAL RAINFOREST TREE SPECIES TO A LIGHT GRADIENT .......16 Introduction.................................................................................................................16 Methods ......................................................................................................................21 Study Site.............................................................................................................21 Study Species.......................................................................................................21 Shadehouse Experiment ......................................................................................21 Photosynthetic Gas Exchange .............................................................................22 Growth Analysis..................................................................................................23 Nutrient Content ..................................................................................................23 Statistical Analysis ..............................................................................................24 Results.........................................................................................................................24 v Photosynthetic Response.....................................................................................24 Growth Patterns...................................................................................................25 Discussion...................................................................................................................26 3 POTENTIAL FOR SUBTROPICAL RAINFOREST RESTORATION ON ABANDONED AGRICULTURAL LANDS IN NEW SOUTH WALES, AUSTRALIA..............................................................................................................38 Introduction.................................................................................................................38 Materials and Methods ...............................................................................................40 Study Site.............................................................................................................40 Species.................................................................................................................40 Photosynthetic Gas Exchange .............................................................................41 Nutrient Content ..................................................................................................41 Statistical Analysis ..............................................................................................42 Results.........................................................................................................................42 Discussion...................................................................................................................43 4 SUMMARY AND CONCLUSIONS.........................................................................53 APPENDIX NUTRIENT CONCENTRATION...............................................................57 LIST OF REFERENCES...................................................................................................59 BIOGRAPHICAL SKETCH .............................................................................................68 vi LIST OF TABLES Table page 2-1 Life-history data for the study species .....................................................................31 2-2 Total dry biomass production (g), relative growth rate between 0 to 96 days (RGR, mg g-1 d-1), specific leaf area (SLA, cm2 g-1), leaf mass ratio (LMR), stem mass ratio (SMR), root mass ratio (RMR), total stem height (cm), and total stem diameter (mm) shown by the six species at 96 days of growth under high light (HL—60%), medium light (ML—30%), and low light (LL—10%)...............32 2-3 Leaf-level photosynthetic parameters: Light saturated rate of photosynthesis (Amax, µmol CO2 m-2 s-1), apparent quantum yield (Aqe, (µmol CO2 m-2 s- 1)/(µmol m-2 s-1)), and light compensation point (LCP, µmol m-2 s-1) shown by the six species grown under high light (HL — 60% full sunlight), medium light (ML — 30% full sunlight), and low light (LL — 10% full sunlight)..............33 3-1 Life-history data for the study species .....................................................................47 3-2 Leaf-level photosynthetic parameters: Light saturated rate of photosynthesis -2 -1 -2 -1 (Amax, µmol CO2 m s ), apparent quantum yield (Aqe, (µmol CO2 m s )/(µmol m-2 s-1)), and light compensation point (LCP, µmol m-2 s-1) shown by the seven species grown under 75% full sunlight. ...................................................................47 A-1 Total nutrient concentration in leaves of six subtropical rainforest species grown under HL (60%), ML (30%) and LL (10%) full sunlight ........................................57 A-2 Total nutrient concentration in leaves of seven subtropical rainforest species grown under 75% full sunlight.................................................................................58 vii LIST OF FIGURES Figure page 2-1 Relative growth rate (mean (SE)) of seedlings of six Australian subtropical rainforest trees, grown at 60%, 30%, and 10% of full sunlight ...............................34 2-2 A) Diameter growth in (mm) and B) height growth in (cm) (mean (SE)) of seedlings of six Australian subtropical rainforest trees grown at 60%, 30%, and 10% full sunlight ......................................................................................................35 2-3 Light response curve of photosynthesis as a function of PPFD for A) Elaeocarpus grandis, B) Flindersia schottiana and C) Gmelina leichhardtii grown