title: A new theory of plant-microbe nutrient competition resolves inconsistencies between observations and model predictions.
abstract: Terrestrial plants assimilate anthropogenic CO2through photosynthesis and synthesizing new tissues. However, sustaining these processes requires plants to compete with microbes for soil nutrients, which therefore calls for an appropriate understanding and modeling of nutrient competition mechanisms in Earth System Models (ESMs). Here, we survey existing plant-microbe competition theories and their implementations in ESMs. We found no consensus regarding the representation of nutrient competition and that observational and theoretical support for current implementations are weak. To reconcile this situation, we applied the Equilibrium Chemistry Approximation (ECA) theory to plant-microbe nitrogen competition in a detailed grassland15N tracer study and found that competition theories in current ESMs fail to capture observed patterns and the ECA prediction simplifies the complex nature of nutrient competition and quantitatively matches the15N observations. Since plant carbon dynamics are strongly modulated by soil nutrient acquisition, we conclude that (1) predicted nutrient limitation effects on terrestrial carbon accumulation by existing ESMs may be biased and (2) our ECA-based approach may improve predictions by mechanistically representing plant-microbe nutrient competition.
authors.affiliation: Climate and Ecosystem Sciences Division, Climate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Climate and Ecosystem Sciences Division, Climate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Riley
authors.affiliation: Climate and Ecosystem Sciences Division, Climate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA.
authors.forename: Jinyun
authors.initials: J
authors.lastname: Tang
mesh_terms: D065948:Grassland; D008954:Models, Biological; D009587:Nitrogen Isotopes; D000078622:Nutrients / Q000378:metabolism; D018521:Plant Physiological Phenomena; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D009587:Nitrogen Isotopes; D000078622:Nutrients; D012987:Soil; C000615243:Nitrogen-15
keywords: 15N tracer; earth system model; grassland; microbial N uptake; nutrient competition model; nutrient competition theory; plant N uptake; plant-microbe competition