PLANT GROWTH AND CLIMATE CHANGE
CONTENTS 1 RECENT AND FUTURE CLIMATE CHANGE AND THEIR IMPLICATIONS FOR PLANT GROWTH 1 1 INTRODUCTION 1 2 THE CLIMATE SYSTEM 1 3 MECHANISMS OF ANTHROPOGENIC CLIMATE CHANGE 1 4 RECENT CLIMATE CHANGES 1 5 FUTURE CHANGES IN ANTHROPOGENIC FORCING OF CLIMATE 1 5 1 FUTURE GLOBAL CLIMATE SCENARIOS 1 5 2 FUTURE REGIONAL CLIMATE SCENARIOS 1 6 CONCLUDING COMMENTS REFERENCES 2 PLANT RESPONSES TO RISING ATMOSPHERIC CARBON DIOXIDE 2 1 INTRODUCTION 2 1 1 OVERVIEW OF PLANT BIOLOGY 2 1 2 A WORD ABOUT METHODOLOGY 2 2 GENE EXPRESSION AND CARBON DIOXIDE 2 3 CELLULAR PROCESSES: PHOTOSYNTHETIC CARBON REDUCTION (PCR) AND CARBON DIOXIDE 2 3 1 C3 PHOTOSYNTHESIS 2 3 2 C4 PHOTOSYNTHESIS 2 3 3 CRASSULACEAN ACID METABOLISM PHOTOSYNTHESIS 2 4 CELLULAR PROCESSES: PHOTOSYNTHETIC CARBON OXIDATION (PCO) AND CARBON DIOXIDE 2 5 1 LEAF CARBON DYNAMICS 2 5 2 INHIBITION OF DARK RESPIRATION 2 5 3 LEAF CHEMISTRY 2 6 1 PLANT DEVELOPMENT 2 6 2 CARBON DYNAMICS 2 6 3 STOMATAL REGULATION AND WATER USE 2 7 PLANT-TO-PLANT INTERACTIONS 2 7 1 PLANT COMPETITION: MANAGED SYSTEMS 2 7 2 PLANT COMPETITION: UNMANAGED SYSTEMS 2 7 3 HOW DOES CO2 ALTER PLANT-TO-PLANT INTERACTIONS? 2 8 1 MANAGED PLANT SYSTEMS 2 8 2 WATER USE IN MANAGED SYSTEMS 2 8 3 UNMANAGED PLANT SYSTEMS 2 8 4 WATER USE IN UNMANAGED PLANT SYSTEMS 2 8 5 OTHER TROPHIC LEVELS 2 9 GLOBAL AND EVOLUTIONARY SCALES 2 9 1 RISING CO2 AS A SELECTION FACTOR 2 9 2 GLOBAL IMPACTS 2 10 UNCERTAINTIES AND LIMITATIONS 3 SIGNI?CANCE OF TEMPERATURE IN PLANT LIFE ¨ 3 1 TWO PARADOXES 3 1 1 PARADOX 3 1 2 PARADOX 3 2 BASELINE RESPONSES OF PLANT METABOLISM TO TEMPERATURE 3 2 1 PHOTOSYNTHESIS 3 2 2 DARK RESPIRATION 3 3 THERMAL ACCLIMATION OF METABOLISM 3 4 GROWTH RESPONSE TO TEMPERATURE 3 5 TEMPERATURE EXTREMES AND TEMPERATURE THRESHOLDS 3 6 THE TEMPERATURES EXPERIENCED BY PLANTS 3 7 TEMPERATURE AND PLANT DEVELOPMENT 3 8 THE CHALLENGE OF TESTING PLANT RESPONSES TO TEMPERATURE 4 TEMPERATURE AND PLANT DEVELOPMENT: PHENOLOGY AND SEASONALITY 4 1 THE ORIGINS OF PHENOLOGY 4 2 RECENT CHANGES IN PHENOLOGY 4 3 ATTRIBUTION OF TEMPORAL CHANGES 4 3 1 DETECTION OF PHENOLOGICAL CHANGE 4 3 2 ATTRIBUTION OF YEAR-TO-YEAR CHANGES IN PHENOLOGY TO TEMPERATURE AND OTHER FACTORS 4 3 3 CONFOUNDING FACTORS 4 4 EVIDENCE FROM CONTINUOUS PHENOLOGICAL MEASURES 4 5 POSSIBLE CONSEQUENCES 5 RESPONSES OF PLANT GROWTH AND FUNCTIONING TO CHANGES IN WATER SUPPLY IN A CHANGING CLIMATE 5 1 INTRODUCTION: A CHANGING CLIMATE AND ITS EFFECTS ON PLANT GROWTH AND FUNCTIONING 5 2 GROWTH OF PLANTS IN DRYING SOIL 5 2 1 HYDRAULIC REGULATION OF GROWTH 5 3 WATER RELATIONS OF PLANTS IN DRYING SOIL 5 3 1 WATER MOVEMENT INTO AND THROUGH THE PLANT 5 3 2 CONTROL OF GAS EXCHANGE BY STOMATA UNDER DROUGHT 5 4 WATER RELATION TARGETS FOR PLANT IMPROVEMENT IN WATER SCARCE ENVIRONMENTS 5 5 CONTROL OF STOMATA, WATER USE AND GROWTH OF PLANTS IN DRYING SOIL: HYDRAULIC AND CHEMICAL SIGNALLING 5 5 1 INTERACTIONS BETWEEN DIFFERENT ENVIRONMENTAL FACTORS 5 5 2 MEASURING THE WATER AVAILABILITY IN THE SOIL: LONG-DISTANCE CHEMICAL SIGNALLING 5 5 3 THE INTEGRATED RESPONSE TO THE ENVIRONMENT 5 6 CONCLUSIONS: A STRATEGY FOR PLANT IMPROVEMENT AND MANAGEMENT TO EXPLOIT THE PLANT’S DROUGHT RESPONSE CAPACITY 6 WATER AVAILABILITY AND PRODUCTIVITY 6 1 INTRODUCTION 6 2 WATER DE?CITS AND PRIMARY PRODUCTIVITY 6 2 1 NET PRIMARY PRODUCTIVITY 6 2 2 WATER-USE EF?CIENCY 6 3 VARIABILITY IN WATER RESOURCES AND PLANT PRODUCTIVITY 6 3 1 TEMPORAL VARIABILITY IN WATER RESOURCES 6 3 2 VARIABILITY IN SPACE 6 3 3 IN SITU WATER REDISTRIBUTION – HYDRAULIC REDISTRIBUTION 6 4 PLANT COMMUNITIES FACING DROUGHT 6 4 1 SPECIES INTERACTIONS WITH LIMITING WATER RESOURCES 6 4 2 VEGETATION CHANGE AND DROUGHT: IS THERE AN ARID ZONE ‘TREELINE’? 6 5 DROUGHTS AND WILD?RES 6 6 AGRICULTURAL AND FORESTRY PERSPECTIVES 6 6 1 AGRICULTURE 6 6 2 FORESTRY 7 EFFECTS OF TEMPERATURE AND PRECIPITATION CHANGES ON PLANT COMMUNITIES 7 1 INTRODUCTION 7 2 METHODOLOGY 7 3 MECHANISMS OF CHANGE IN PLANT COMMUNITIES 7 3 1 DIRECT EFFECTS OF CLIMATE 7 3 2 INTERSPECI?C DIFFERENCES IN GROWTH RESPONSES TO CLIMATE 7 3 3 COMPETITION AND FACILITATION 7 3 4 CHANGING WATER AVAILABILITY AND INTERACTIONS BETWEEN CLIMATE VARIABLES 7 3 5 INTERACTIONS BETWEEN CLIMATE AND NUTRIENT CYCLING 7 3 6 ROLE OF EXTREME EVENTS 7 3 7 DISPERSAL CONSTRAINTS 7 3 8 INTERACTIONS WITH ANIMALS 7 4 IS COMMUNITY CHANGE ALREADY HAPPENING? ACKNOWLEDGEMENTS 8 ISSUES IN MODELLING PLANT ECOSYSTEM RESPONSES TO ELEVATED CO2: INTERACTIONS WITH SOIL NITROGEN 8 1 INTRODUCTION 8 1 1 MODELLING CHALLENGES 8 1 2 CHAPTER AIMS 8 2 REPRESENTING NITROGEN CYCLING IN ECOSYSTEM MODELS 8 2 1 OVERVIEW OF ECOSYSTEM MODELS 8 2 2 MODELLING NITROGEN CYCLING 8 2 3 MAJOR UNCERTAINTIES 8 3 HOW UNCERTAIN ASSUMPTIONS AFFECT MODEL PREDICTIONS 8 3 1 SCENARIO 1 (BASE CASE): INCREASED LITTER QUANTITY AND DECREASED LITTER QUALITY 8 3 2 SCENARIO 2: SCENARIO 1 + HIGHER LITTER N/C RATIO 8 3 3 SCENARIO 3: SCENARIO 1 + INCREASED ROOT ALLOCATION 8 3 4 SCENARIO 4: SCENARIO 1 + INCREASED N INPUT 8 3 5 SCENARIO 5: SCENARIO 1 + DECREASED N/C RATIO OF NEW ACTIVE SOM 8 3 6 SCENARIO 6: SCENARIO 5 + DECREASED N/C RATIO OF NEW SLOW SOM 8 3 7 SCENARIO 7: SCENARIO 2 + 3 + 4 + 6 + DECREASED SLOPE OF RELATION BETWEEN MAXIMUM LEAF POTENTIAL PHOTOSYNTHETIC ELECTRON TRANSPORT RATE AND LEAF N/C RATIO 8 4 MODEL–DATA FUSION TECHNIQUES 8 5 DISCUSSION 9 PREDICTING THE EFFECT OF CLIMATE CHANGE ON GLOBAL PLANT PRODUCTIVITY AND THE CARBON CYCLE 9 1 INTRODUCTION 9 2 DE?NITIONS AND CONCEPTUAL FRAMEWORK 9 3 EMPIRICAL BASIS OF OUR KNOWLEDGE OF CARBON ?UXES 9 3 1 NPP 9 3 2 NEP AND NEE 9 3 3 GPP AND NPP BY REMOTE SENSING 9 3 4 USE OF MODELS TO PREDICT CHANGES IN PLANT GROWTH AND CARBON ?UXES AT THE LARGE SCALE 9 4 DEPENDENCIES OF ?UXES ON CO2, LIGHT AND NITROGEN SUPPLY 9 4 1 PHOTOSYNTHESIS 9 4 2 AUTOTROPHIC RESPIRATION 9 4 3 HETEROTROPHIC RESPIRATION 9 4 4 ECOSYSTEM MODELS 9 5 CONCLUSIONS