A novel representation of biological nitrogen fixation and competitive dynamics between nitrogen-fixing and non-fixing plants in a land model (GFDL LM4.1-BNF)

Abstract. Representing biological nitrogen fixation (BNF) is an important challenge for coupled carbon (C) and (N) land models. Initial representations of BNF in models applied simplified phenomenological relationships. More recent are mechanistic include the dynamic response symbiotic to N limitation plant growth. However, they generally do not competitive dynamics between N-fixing non-fixing plants, which a key ecological mechanism that determines ecosystem-scale BNF. Furthermore, asymbiotic included Here, we present LM4.1-BNF, novel representation (asymbiotic symbiotic) updated cycling Geophysical Fluid Dynamics Laboratory Land Model 4.1 (LM4.1). LM4.1-BNF incorporates by soil microbes, distinct temperature responses derived from corresponding observations. makes reasonable estimations major pools fluxes their temporal dynamics, comparison previous version LM4.1 with (LM3-SNAP) (phenomenological those without plants and/or BNF) at temperate forest site. effectively reproduces rate (13 kgNha-1yr-1) observations (11 kgNha-1yr-1). rate: simulates pulse early succession reaches 73 kgNha-1yr-1 15 years then declines ∼0 300 years, similarly observed BNF, 75 17 late successional forests. As such, can be project vegetation growth degree this will constrain terrestrial C sink under elevated atmospheric CO2 concentration other global change factors.