Mathematical Modelling of Climate Change Impacts on Terrestrial Ecosystems

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My research is dedicated to developing and testing a comprehensive model (ecosys) of diverse natural and managed terrestrial ecosystems. Model hypotheses are formulated as much as possible from basic theory in physics, chemistry and biology by which ecosystem behaviour is governed. Consequently model parameterization is largely independent of model development, thereby avoiding algorithms and parameters that are artifacts of model formulation. It is therefore capable of well-constrained tests against detailed process-level observations as proposed here. Such models can make a valuable contribution to the study of climate change impacts, particularly those in the arctic which is projected to warm at a rate twice that of the global average in the next century. These impacts are being studied in the US DoE's Next Generation Ecosystem Experiment (NGEE) Arctic, a key objective of which is ‘to advance a robust predictive understanding of Earth’s climate and environmental systems by delivering a process-rich ecosystem model … in which the evolution of Arctic ecosystems in a changing climate can be modeled’. I propose to further develop our capability to model climate change impacts on diverse arctic ecosystems through participation in NGEE Arctic by using ecosys to address the five scientific questions upon which NGEE is based: (1) How does the structure and organization of the landscape control the storage and flux of carbon and nutrients in a changing climate? (2) What will control rates of CO2 and CH4 fluxes across a range of permafrost conditions? (3) How will warming and permafrost thaw affect above- and belowground plant functional traits, and what are the consequences for Arctic ecosystem carbon, water, and nutrient fluxes? (4) What controls the current distribution of Arctic shrubs, and how will shrub distributions and associated climate feedbacks shift with expected warming in the 21st century? (5) Where, when, and why will the Arctic become wetter or drier, and what are the implications for climate forcing? For each question, I have developed model hypotheses in ecosys and testing protocols with data acquired in NGEE Arctic. These protocols will be conducted at plot, landscape and regional scales using diverse experimental observations of thermal, hydrological and biological dynamics (soil temperature, water and ice content, active layer depths, ecosystem productivity, energy and greenhouse gas exchange, microbial and plant functional types). The process levels at which these hypotheses are formulated and tested are more detailed and comprehensive than those of previous arctic modelling studies, and will greatly improve confidence in our projections of climate change impacts on arctic ecosystems. Ecosys will make direct contributions to these projections through its coupling with the USDoE's Community Earth System Model CESM currently underway at the Lawrence Berkeley National Lab.