lo..t Water use strategy of Meløleuca halmøturorum in a saline swamp. submitted by Lisa Jane Mensforth BAppSc (Nat Res Man), BSc (Hons) as requirement in full for the degree of Doctor of Philosophy in the Botany Department The University of Adelaide November 1996 ii TABLE OF CONTENTS Page TABLE OF CONTENTS ...........ii LIST OF TA8L8S............ ..... VII LIST OF FIGUR8S............ ...V[I ABSTRACT .............. .............X[r DECLARATION OF ORIGINALITY .... XV PTJBLICATIONS ASSOCIATED \ryITH THIS TIIESIS .......XVI ACKNOWLEDGMENTS............ XVII CHAPTER L: GENERAL INTRODUCTION AND LITERATURE R8VIEW........... L l.L General Background............ .................1 L.2 Ecophysiological Response to Salinity and Waterlogging .......................1 1.2.1 lon andwater relations... 2 1.2.2. Plant growth andwater use 4 1.2.3 Anatomy andmorphology adaptations: Response of the root system...................... ó L.3 Water use strategies of trees in saline and waterlogged environments ...................7 l. 3. I Natural systems... I (a) Coastal environments............. 8 (b) Floodplain environments 10 1. 3.2 Agricultural Systems ..... 11 (a) Trees and shrubs ........ 11 (b) Salt tolerant crops and pastures....... 14 1.4 Melaleuca halmaturorum 17 L.5 Aims of this project and rationale for methodology............. .................. 19 CHAPTER 2: SITE DESCRIPTION ......21 2.1 Environmental Description of the Upper South East of South Australia ..............2I 2.1.1 Climate 21 2.1.2 Topography and Soils 21 2. 1. 3 Hydrolo 9y .......... 25 (a) Surface water... 25 (b) Groundwater 27 2.1.4 Vegetation of the Upper South 8ast.......... 2.1.5 Effect of Rising Groundwater on Melaleuca communities ilt (a) Healthof mature M. halmaturorum....... 37 (b) Community composition and regeneration of M. halmaturorum 37 2.2 Description of specific study sites.......... 40 CHAPTER 3: TREE WATER USE 46 3.1, Introduction ........ 46 3.1.1. Mechanisms of tree water use............ .................... 46 3.L1. Measurement of transpiration andproblems of scale.. .................... 50 3.2. I P ot ential Ev ap o trans piration ........... 53 3.2.2 Heat pulse: estimated single treeflux.... 54 (a) Sap velocity..... 54 (b) Sap flux...... 55 3.2.3 Stand Transpiration: Scaling single tree heat pulse estimates................ 56 (a) Scaling experiment: Duck Island ............ 56 (b) Seasonal transpiration and other sites..... 51 3.2.4 Leaf resistqnce: NuIl balance porometer 58 (a) Leaf resistance 58 (b) Estimated transpiration rates ..................... 59 3.2.5 Water (Jse Efficiency: ô1rC.......... ..................... 6 I 3. 3. I P otential Evapotranspiration ( P ET) ..... 61 3.3.2 Heat pulse: estimated single treeflux.... 61 (a) Sap velocity..... .',,',61 ......63 3.3.3 StandTranspiration: Scaling single tree sapflux estimates ......67 (a) Scaling experiment: Duck Island....... ......67 (b) Seasonal transpiration and other sites 70 3. 3.4 Stomatal resistance ........... 77 (a) Single leafresistances at all sites... 77 (b) Estimated canopy resistances and areal transpiration rates. 83 3.3.5 Wøter Use Efficiency. ..83 3.4 Discussion.......... ..................84 3.4.1 Using the heat pulse method to estimate transpiration in saline environments .... 84 3.4.2 Ecophysiological response o/ M.halmaturorum to groundwater salinity and 88 iv 3.5 Summary and conclusion ....90 CIIAPTER 4: SOIL AND PLANT WATER STATUS.. .............9I 4.1 Introduction .......91 4.1.1 SoiI and plant water potentia\............... 92 (a) Soil water potential 92 (b) Plant water potential 93 4.1.2 Otherfactors affecting water availability to roots 9s 4.2.1 Groundwater depth and salinity ...96 4.2.2 SoiI water potential.......... 96 (a) Matric Potential... 96 (b) Osmotic potential. .91 4.2. 3 Leaf water potential.......... 97 (a) Pressure bomb................ ,.,..''.'.''...'.'.'. 9] (b) Pressure-Volume Curves .........,........... 98 4.2.4 SoiI waterlo g ging ............. .,'..'.........','.,. 99 (a) Ferrous iron indicator.............. ..................... 99 4.3.1 Groundwater depth and salinity ... 100 4.3.2 Soil water potential.... 101 4.3.3 Leaf water potential ................. 105 4.3.4 SoiI waterlogging.. ................. 107 (a) Ferrous iron test...... ................. 107 (b) Redox (Eh) and pH, ................. 108 4.4 Discussion.......... ................. 110 4.4.1 Availability of water sources in a saline swamp.'..... .".'.' 110 4.4.2 Ecophysiological implications for M. halmaturorum 115 4.5 Summary and Conclusions............. ...116 CHAPTER 5: ROOT WATER UPTAKE; IDENTIFICATION OF \ryATER SOURCES ............... ................tL7 5.l lntroduction ....I17 5.1.1 Tree water sources 117 5.1.2 Stable isotopes to identifu water sources 118 V 5.2. I Stable Isotopes ........ 12I (a) Fractionation glasshouse experiment: Validation of technique under saline waterlogged conditions T2T (b) Field study 123 5.2.2 Root mass measurements: SoiI coring .. 12s 5.2. 3 Ro ot Ob s erv ation : Chamber............. 125 5.3.1 Stable Isotopes .. 125 (a) Validation of isotope technique ................... t25 (b) Isotope Field Studies ................. r28 5.3.2 Root mass measurements..... 136 5. 3. 3 Root Observation .................. 136 5.4.1 Interpretation of Sources of Water 137 5.4.2 Ecophysiolo gical implications for M. halmaturorum.......... 142 CIIAPTER 6Z MODELLING AND QUANTIF"TING GROUNDWATER DISCH4RG8...........................; ................146 6.1,Introduction ....146 6.1.1 Key results from each site.. 146 (a) Duck Island 146 (b) Hansons ... r41 (c) Lesron... ... t47 6.1.2 General water use strategy r49 6.2. I Modelling groundwater discharge.. 150 6.2.2 Model As sumptiot?.s.............. ... 154 6.2.3 Model Theory 156 6.2.4 M odel Validqtion and Quantifyinç Gn,,..... 157 6.2.5 Model Parameters . 1s8 6.3.1 Duck Island. 159 6.3.2 Hansons ...... 163 6.3.3 Lesron.. 170 VI 6.4.1 Implications of model for role of trees in the water balance...... 173 6.4.2 Implications of modelfor M. halmaturorum water use strategy 174 6.5 Summary and Conclusions............. ...177 CHAPTER 7: GENERAL DISCUSSION AND CONCLUSIONS ...........178 7.1 Groundwater discharge and the water use strategy of M. halmaturorum..........178 7.2 Sustainability of trees in groundwater discharge areas and implications for wetland health...... ...182 7.3 Ecophysiological survival strategies in response to environmental stresses and changes.... ................. 184 7.4 Conclusions......... ................ L86 T.Slmplications for Management ............1,88 7.6 Further Work.... .................188 APPENDIX I . FIELD STUDY PROGRAMME....... ................189 APPENDIX II . RAINFALL AT JAFFREYS S\ryAMP ...........190 APPENDTX rrr . HEAT PULSE TECHNIQUE........... ............. 191 APPENDIX IV . SCALING DATA FOR ALL TREF-S............ .................193 APPENDIX V . ACTUAL EVAPOTRANSPIRATION; BOWEN RATIO.... .......... I94 APPENDIX VI . SOIL PROFILES FOR ALL SITF,S AT ALL SAMPLING TIMES.197 REFERENCES ......... ...............214 vil List of Tâbles page Table 2.1: Site characterisation, indicated as predicted degree of salinity and waterlogging, for all sites. ......... 42 Table 3.1: Regression relationships between scalars and flux for each tree parameter and estimated flux indicating the slope and 12 of the relationship, the estimated total flux from the plot (L/day), the estimated a¡eal flux from the plot (mm/day), and the standard deviation and standard effor on this estimate. The mean actual evapotranspiration from the Bowen ratio is also shown ...........67 Table 3.2: Estimated tree density (treet rt), circumference density (per ground area; mmtrÊ¡, sapwood density (area per ground atea; cnflnh, leaf area per ground area (leaf areaindex; r#tt*),andcanopyprojection frÊn*>. .......73 Table 3.3: Average daily water use and standard deviation for summer and autumn (December to May) and winter and Spring (June to November) at each site. .............77 Table 4.1: Pressure Volume (PV) curve analysis data for shoots taken on 8.3.96 (summer) and 31.10.95 (winter) at Duck Island and rehydrated. Pre dawn leaf water potential (MPa) was also taken on this day and is shown. .................... 105 Table 4.2: Summary on water availability (depth interval; m) of all water sources for each sampling time at Duck Island (a), Hansons (b), Lesron (c), and Jaffray (d). ........... .. Ll4 Table 5.1: Water sources for each sampling time (depth interval; m) based on the isotope technique combined with information of soil water availability 140 Table 6.1: Quantity of groundwater used (G; mm) for each month as determined by the 7o of groundwater use at each sampling time and the monthly transpiration. ................ 148 Table 6.2: Description of all parameters discussed in chapter and used in the model their definition and dimensions. 151 Table 6.3: Values of model parameters used for each of the sites..... .............. 159 vilt List of Figures page Figure 1. 1: Outline of thesis chapters 20 Figure 2.1: The Upper South-East of South Australia... ..................22 Figure 2.2: Site locations (indicated by trees), associated watercourses and wetlands (dashed lines), and surface water flows between wetlands (arrows) in the Upper South- East of South Australia....... 23 Figure 2.3: Cross section of a dune/ inter-dunal flat complex in the upper south-east of South Australia indicating groundwater recharge (downward arrows), groundwater discharge (upward arrows) and other groundwater flows (Kennett Smith etaI,1995).28 Figure