From lilliput to brobdingnag: Extending models of mycorrhizal function across scales

Mycorrhizae occur in nearly all terrestrial ecosystems. Resource exchange between host plants and mycorrhizal fungi influences community, ecosystem, and even global patterns and processes. Understanding the mechanisms and consequences of mycorrhizal symbioses across a hierarchy of scales will help predict system responses to environmental change and facilitate the management of these responses for sustainability and productivity. Conceptual and mathematical models have been developed to help understand and predict mycorrhizal functions. These models are most developed for individual- and population-scale processes, but models at community, ecosystem, and global scales are also beginning to emerge. We review seven types of mycorrhizal models that vary in their scale of resolution and dynamics, and discuss approaches for integrating these models with each other and with general models of terrestrial ecosystems.