Nutrient Dynamics in a Coupled Terrestrial Biosphere and Land Model (ELM-FATES)
Ryan Knox1, Charles Koven1, Anthony Walker2* (firstname.lastname@example.org), William Riley1, Joseph Wright3, Jennifer Holm1, Xinyuan Wei2, Rosie Fisher4, Qing Zhu1, Jinyun Tang1, Danial Ricciuto2, Jacquelyn Shuman5, Xiaojuan Yang2, Lara Kueppers1, Jeffrey Chambers1
1Lawrence Berkeley National Laboratory, Berkeley, CA; 2Oak Ridge National Laboratory, Oak Ridge, TN; 3Smithsonian Tropical Research Institute, Ancon, Panama; 4CICERO Center for International Climate Research, Oslo, Norway; 5National Center for Atmospheric Research, Boulder, CO
Researchers present a representation of nitrogen and phosphorus cycling in the vegetation demography model FATES within the E3SM Land Model (ELM-FATES). This representation is modular and designed to allow testing of multiple hypothetical approaches for carbon-nutrient coupling in plants. The model tracks nutrient uptake, losses via turnover from both live plants and mortality into soil decomposition, and allocation during tissue growth for numerous size- and functional-type-resolved plant cohorts within a time-since-disturbance-resolved ecosystem. Root uptake is governed by fine root biomass. The research team hypothesized a proportional-integral-derivative controller to allow plants to dynamically vary their fine root carbon allocation in order to balance carbon and nutrient limitations to growth. The sensitivity of the model was tested to a wide range of parameter variations and structural representations and in the context of observations at Barro Colorado Island, Panama. A key model prediction is that plants in the high-light-availability canopy positions allocate more carbon to fine roots than plants in low-light understory environments, given the widely different carbon versus nutrient constraints of these two niches within a given ecosystem. This model provides a basis for exploring carbon-nutrient coupling with vegetation demography within Earth system models.