We propose bringing together leading scientists from both the experimentalist and modelling communities in the fields of mycorrhizal ecology, biogeochemistry, eco-hydrology and global change biology to identify the potential, the challenges and the limitations associated with conceptualizing and parameterizing belowground dynamics (specifically, mycorrhizal dynamics) in large-scale models.
Mycorrhizal fungi form symbiotic associations with nearly all land plants and play a crucial role in coupling the carbon (C), nitrogen (N), phosphorus (P) and hydrological cycles. Despite their importance at local scales, mycorrhizal dynamics are absent in current earth system modelling. We propose bringing together leading scientists from both the experimentalist and modelling communities in the fields of mycorrhizal ecology, biogeochemistry, eco-hydrology and global change biology to identify the potential, the challenges and the limitations associated with conceptualizing and parameterizing belowground dynamics (specifically, mycorrhizal dynamics) in large-scale models.
Rationale and scope
Understanding the role of terrestrial ecosystems in removing carbon dioxide (CO2) from the atmosphere is critical for predicting future changes in the Earth’s climate. Current estimates of future carbon (C) uptake by the terrestrial biosphere differ by an order of magnitude from one global model to the next, resulting in high uncertainties in predictions of climate change feedbacks. This variability can be attributed largely to how models represent belowground C dynamics and nutrient limitation. Most current models include only coarse-grained representations of belowground processes (if any), even though roots and their microbial associates are critical to coupling C and nutrient cycles in ecosystems. Likewise, no current models include coupled representations of C and other nutrient cycles (e.g. N and P), despite the well-known importance of C-N-P linkages in mediating ecosystem response to global environmental changes.
Arguably the most important group of soil microbes that link C-N-P cycles is mycorrhizal fungi. Mycorrhizal fungi form mutualistic relationships with plants, receiving C from their plant hosts in exchange for growth-limiting soil nutrients such as N and P. These fungi receive 10-25% of plant photoassimilates and constitute a major pathway by which C is stored in fungal biomass and soils. Moreover, mycorrhizal fungi also influence the decomposition of soil organic matter by releasing extracellular enzymes or binding together soil particles into stable aggregates. Finally, mycorrhizal fungi alleviate environmental stressors such as drought by enhancing water and nutrient uptake, improving contact between plant tissues and soil particles, and altering the water-holding capacity of soils. Despite the known importance of mycorrhizal dynamics, plant-mycorrhizal interactions (and their impact on nutrient cycling) are absent in models underpinning our predictive capacity to estimate C storage and climate change. Investigating how mycorrhizal fungi link C-N-P cycles will thus improve predictions of the terrestrial carbon sink.
Dr K. Rebel, Dr R.P. Philips and Prof. M. van der Heijden (University Utrecht)
Travel and lodging are supported by the US Department of Energy, Office of Science, Office of Biological and Environmental Research.