WE PROPOSE TO INVESTIGATE THE VARIABILITY OF ANTICIPATED CHANGES IN VEGETATION PATTERNS OF PRODUCTIVITY STRUCTURE AND DISTRIBUTION ALONG THE TAIGA-TUNDRA ECOTONE (TTE). OUR PROJECT WILL USE AIRBORNE AND SPACEBORNE REMOTE SENSING DATA ON THE LOCATION EXTENT AND PATTERN OF WOODY COVER TO THE BIOME BOUNDARY TO CONTROL THE APPLICATION OF A HIGH RESOLUTION SPATIALLY EXPLICIT INDIVIDUAL-BASED GAP MODEL FOR PREDICTING THE MAGNITUDE AND VARIABILITY OF CHANGES IN STRUCTURE WITHIN THE TTE. SHIFTS IN THE TTE ARE OCCURRING AND ANTICIPATED AS ARCTIC WARMING PERSISTS THROUGH THE NEXT CENTURY (ELMENDORF ET AL. 2012 EVJU ET AL. 2012 KAARLEJARVI ET AL. 2012 DIFFENBAUGH ET AL. 2013). SOME STUDIES PREDICT THAT UP TO ~50% OF THE TUNDRA COULD BE COLONIZED BY TREES BY 2100 (IPCC 2014). HOWEVER THE SPATIAL DISTRIBUTION OF TTE CHANGE IS NONLINEAR AND HETEROGENEOUS EXHIBITING DIFFERENT RATES DIRECTIONS AND DRIVERS (E.G. PERMAFROST ELEVATION MICRO-CLIMATE SOILS ETC.). THESE AND FUTURE CHANGES DRIVEN BY MULTISCALE INFLUENCES NEED TO BE EXAMINED IN THE CONTEXT OF SITE-SCALE PATTERNS OF CURRENT STRUCTURE AND PRODUCTIVITY IN BOTH TUNDRA AND FORESTS. THE GOAL OF THIS WORK WILL BE TO EXAMINE AND QUANTIFY THE LIKELIHOOD OF PREDICTED CHANGES IN TTE FOREST STRUCTURE PATTERNS OCCURRING WITHIN THE ABOVE EXTENDED DOMAIN USING AIRBORNE IMAGERY AND LIDAR OBSERVATIONS SITE-SCALE (I.E. HIGH RESOLUTION SPATIALLY-EXPLICIT INDIVIDUAL-BASED) FOREST AND TUNDRA VEGETATION MODELING AND A LANDSAT-DERIVED MAP OF THE EXTENT&PATTERN OF THE TTE. USING THE MAPPED EXTENT OF THE TTE TO SPATIALLY GUIDE OUR MODELLING OUR SPECIFIC OBJECTIVES ARE TO: 1. PARAMETERIZE THE SPATIALLY-EXPLICIT INDIVIDUAL-BASED GAP MODEL SIBBORK FOR THE TTE FOREST STUDY SITES USING LEVERAGED FIELD DATA AND FOREST STRUCTURE DERIVED FROM LVIS AND GLIHT DATASETS. 2. IMPROVE PERMAFROST ALLOMETRY ROUTINES INTRODUCE LITTERFALL AND INTEGRATE THE ARCVEG (TUNDRA) MODEL PARAMETERS INTO THE SIBBORK (FOREST) MODEL TO EXTEND THE SIMULATION DOMAIN ACROSS THE FULL TUNDRA-TAIGA BOUNDARY AT THE INDIVIDUAL SCALE. 3. PREDICT FUTURE FOREST AND TUNDRA PRODUCTIVITY AND ECOTONE LOCATION USING CMIP6 PROJECTIONS. 4. QUANTIFY THE ABILITY OF THE TREE COVER ABRUPTNESS VARIABLE TO PREDICT PATTERNS OF TTE CHANGE. CALIBRATED WITH AN ABOVE AIRBORNE PRODUCT (LVIS) AND INITIALIZED WITH A LANDSAT-DERIVED MAP OUR MODELING FRAMEWORK WILL DELIVER THE FIRST HIGH RESOLUTION SPATIALLY-EXPLICIT FOREST AND TUNDRA MODEL THAT HAS THE CAPABILITY TO MODEL ECOTONE SHIFT ACROSS THE ABOVE STUDY DOMAIN. OUR RESEARCH WILL PROVIDE A DEEPER UNDERSTANDING OF THE CURRENT PRODUCTIVITY DYNAMICS ALONG THE TTE AND ALLOW FOR INFORMED PROGNOSTICATION ABOUT THE SHIFT IN THE EXTENT OF TREE COVER AND THE SPATIAL VARIABILITY IN THE DIRECTION RATE AND MAGNITUDE OF THESE SHIFTS.