Embracing fine-root system complexity in terrestrial ecosystem modelling.
Bin WangM Luke McCormackDaniel M RicciutoXiaojuan YangColleen M IversenPublished in: Global change biology (2023)
Projecting the dynamics and functioning of the biosphere requires a holistic consideration of whole-ecosystem processes. However, biases towards leaf, canopy, and soil modelling since the 1970s have constantly left fine-root systems being rudimentarily treated. As accelerated empirical advances in the last two decades establish clearly functional differentiation conferred by the hierarchical structure of fine-root orders and associations with mycorrhizal fungi, a need emerges to embrace this complexity to bridge the data-model gap in still extremely uncertain models. Here, we propose a 3-pool structure comprising Transport and Absorptive fine roots with Mycorrhizal fungi (TAM) to model vertically-resolved fine-root systems across organizational and spatial-temporal scales. Emerging from a conceptual shift away from arbitrary homogenization, TAM builds upon theoretical and empirical foundations as an effective and efficient approximation that balances realism and simplicity. A proof-of-concept demonstration of TAM in a big-leaf model both conservatively and radically shows robust impacts of differentiation within fine-root systems on simulating carbon cycling in temperate forests. Theoretical and quantitative support warrants exploiting its rich potentials across ecosystems and models to confront uncertainties and challenges for a predictive understanding of the biosphere. Echoing a broad trend of embracing ecological complexity in integrative ecosystem modelling, TAM may offer a consistent framework where modelers and empiricists can work together towards this grand goal.