THE EARTH SYSTEM MODELS (ESMS) USED TO MAKE CLIMATE PROJECTIONS INCORPORATE A WIDE RANGE OF ATMOSPHERIC AND ENVIRONMENTAL PROCESSES. HOWEVER SOME KNOWN POTENTIALLY IMPORTANT PROCESSES ARE STILL OMITTED BECAUSE THEY ARE EITHER POORLY UNDERSTOOD OR ARE NOT QUANTIFIED WELL ENOUGH TO WARRANT INCLUSION INTO ESMS. ONE SUCH PROCESS IS THE CHANGE IN SENSITIVITY OF PLANT CARBON EXCHANGE (I.E. PHOTOSYNTHESIS AND RESPIRATION) TO TEMPERATURE AS A RESULT OF ACCLIMATION. THE PROPOSED PROJECT WILL TEST BASIC HYPOTHESES ABOUT PLANT TEMPERATURE ACCLIMATION ACROSS BIOMES AND ITS CONSEQUENCES FOR TERRESTRIAL CARBON UPTAKE USING AN INTERDISCIPLINARY COMBINATION OF PHYSIOLOGICAL ECOLOGICAL AND MODELING TECHNIQUES. THE ULTIMATE GOAL OF THE PROJECT WILL BE TO QUANTIFY THE DEGREE TO WHICH PLANT PHOTOSYNTHESIS AND RESPIRATION ACCLIMATE TO TEMPERATURE WITHIN ALL OF THE PLANT FUNCTIONAL TYPES (PFTS) COMMONLY USED IN ESMS. ONE OF THE END PRODUCTS OF THIS PROJECT WILL BE A SET OF ESM-COMPATIBLE PFT-SPECIFIC ALGORITHMS DESCRIBING THE TEMPERATURE RESPONSE OF THESE TWO PROCESSES TO BOTH SHORT- AND LONG-TERM CHANGES IN TEMPERATURE.THIS PROJECT WILL SUPPORT A SERIES OF GROWTH CHAMBER- AND COMMON GARDEN-BASED MEASUREMENTS ON THE PHYSIOLOGICAL AND ECOLOGICAL RESPONSES TO TEMPERATURE OF A VARIETY OF SPECIES WITHIN ALL OF THE PFTS COMMONLY USED IN ESMS. GROWTH CHAMBER MEASUREMENTS WILL BE USED TO QUANTIFY LONG-TERM TEMPERATURE RESPONSES OF PHOTOSYNTHESIS AND RESPIRATION IN A MANNER USEFUL FOR ESMS. COMMON GARDEN MEASUREMENTS WILL BE USED TO VALIDATE THE GROWTH CHAMBER MEASUREMENTS IN SPECIES GROWN OUTDOORS ACROSS A WIDE RANGE OF CLIMATE ZONES AND TEST FOR DIFFERENCES IN SPECIES AGE ON ACCLIMATORY ABILITY. THESE DATA WILL BE USED TO PARAMETERIZE THE FIRST-EVER PFT-SPECIFIC CARBON EXCHANGE ALGORITHMS THAT INCLUDE TEMPERATURE ACCLIMATION. THESE ALGORITHMS WILL BE SYSTEMATICALLY EVALUATED USING THE LAND MODEL COMPONENT OF MULTIPLE ESMS (CESM AND NOAA/GFDL ESM) IN TERMS OF THEIR ABILITY TO REPRODUCE PAST DATA COMPARED TO COMMONLY USED NON ACCLIMATION ALGORITHMS AT THE GLOBAL REGIONAL AND SITE LEVEL. GLOBAL AND REGIONAL SIMULATIONS WILL BE DRIVEN USING NASA PRODUCTS VIA THE NASA LIS AND COMPARED TO NASA MODIS PRODUCTS INCLUDING MOD16 (EVAPOTRANSPIRATION) AND MOD17 (NET PRIMARY PRODUCTION). SITE-LEVEL SIMULATIONS WILL BE DRIVEN BY HIGH-RESOLUTION REANALYSIS DATA AND COMPARED TO FLUX TOWER OBSERVATIONS. SIMULATIONS WILL ALSO BE PERFORMED TO EXAMINE THE IMPACT OF INCLUDING TEMPERATURE ACCLIMATION ON FUTURE PROJECTIONS USING CMIP5 RCP SCENARIOS.PRELIMINARY WORK HAS SHOWN THAT TEMPERATURE ACCLIMATION OF PHOTOSYNTHESIS AND AUTOTROPHIC RESPIRATION CAN HAVE A MAJOR IMPACT ON FUTURE CLIMATE PROJECTIONS. IN COLLABORATION WITH LEADING RESEARCHERS IN THE ECOLOGICAL AND MODELING FIELDS THIS PROJECT WILL NOT ONLY RESULT IN A THOROUGH GLOBAL EVALUATION OF PHOTOSYNTHESIS AND AUTOTROPHIC RESPIRATION TEMPERATURE ACCLIMATION BUT WILL ALSO PRODUCE THE FIRST-EVER PFT-SPECIFIC ALGORITHMS FOR TEMPERATURE ACCLIMATION. THESE ALGORITHMS WILL BE TESTED AND THOROUGHLY EVALUATED INMULTIPLE MODELS AND WILL BE DESIGNED IN SUCH A WAY THAT THEY CAN BE EASILY INCORPORATED INTO OTHER ESMS INCLUDING NASA'S GISS MODELE. THE END RESULT WILL BE A MAJOR MECHANISTIC IMPROVEMENT OF ESMS THAT WILL ULTIMATELY DECREASE THE UNCERTAINTY OF FUTURE PROJECTIONS OF CLIMATE CHANGE.