First-principle biophysical approach to resolve the global organization of root traits and plant-soil carbon dynamics

The influence of climate on biosphere dynamics depends closely on the organization of plant traits . Recent empirical analyses have demonstrated a high degree of global organization among root functional traits, which may differ markedly from that of aboveground traits. However, the mechanisms that determine th is global pattern of root traits remain elusive. Progress has been particularly hampered by the lack of a broader theory that places the biophysics of individual plant growth strategies with in the larger context of root-microbe symbioses and plant-soil biogeochemical feedbacks. Moreover, existing theories have tended to emphasize the mean-field solution , when local competition and evolution may not necessarily fit that assumption . Here we present a first-principle evolution-based approach that places a trait-based analysis of root biophysics in the context of plant competition for soil resources such as nutrients or water. Using game-theoretic principles, we allow plants to evolve different acquisition strategies, including specific biophysical traits (such as root diameter) and the opportunity to evolve mycorrhizal and rhizobial symbioses, and simulate competition under different local biogeochemical regimes. Our low-dimensional model is capable of recreating several fundamental and emergent aspects of root trait organization and ecosystem plant- resource interactions , including: (i) the dependence of root diameter and specific root length on biome nutrient supply; (ii) the tradeoff between belowground plant carbon investment, root trait s, and mycorrhizal and rhizobia l symbioses; (iii) the link between root traits and soil water conditions ; and (iv) the consequences of plant growth strategies for ecosystem carbon accumulation. Our approach is directly applicable to studies on belowground carbon and nutrient cycling, and has great promise in contributing to the development of next-generation Earth system models.