Influence of Phosphorus Cycle Coupling on Biogeochemistry Feedbacks

Wednesday, May 14, 2014 - 07:00
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Previous modeling efforts indicated an important role for nutrient dynamics in regulating the magnitude and interplay of biogeochemistry-climate system feedbacks. It has been suggested that the inclusion of carbon and nitrogen cycle coupling is a partial step toward a more accurate representation of terrestrial ecosystem dynamics and their influence on climate system feedbacks. Including the additional interactions of a prognostic phosphrus cycle has been hypothesized to move the modeled behavior of global coupled climate-biogeochemistry system closer to the dynamics of the actual Earth system. We have explored these hypotheses by introducing a prognostic phosphorus cycle in the Community Land Model framework, coupling to the existing carbon-nitrogen biogeochemistry mechanisms in CLM4. The model has been parameterized and evaluated at site and global scales. We find that including C-N-P coupling improves model performance in tropical systems where P-limitation is expected (based on observation and experimentation). We also find that many regions exhibit temporal shifts in nutrient limitation, fluctuating between p-limitation and N-limitation on sub- and inter-annual timescales. The influence of C-N-P coupling on global-scale climate feedbacks has yet to be evaluated in a coupled climate modeling context, but offline model results indicate that P-limitation plays an important role in predicted response of land ecosystems to rising CO2 concentration and changing temperature.