A systematic review of mechanistic models of riverine macrophyte growth

Riverine macrophytes play diverse and foundational ecological roles, directly influencing ecosystem properties from local biodiversity to flows of water, energy, nutrients, and sediment, many of which in turn are central to river management. Numerical modeling is thus a crucial tool for understanding macrophyte and ecosystem responses to environmental, ecological, or management changes. However, riverine macrophytes have received relatively limited modeling attention compared to plants in many other aquatic or terrestrial systems. We conducted a systematic review of riverine macrophyte growth models, focusing on mechanisms of macrophyte growth, biomass loss, and feedback effects on river ecosystems. Processes such as light availability, thermal tolerance, nutrient limitation, and mortality were widely included in almost all models meeting the review criteria. However, models varied widely in their inclusion of processes such as shading, scour, and the roles of macrophytes in stream nutrient cycles. There has been relatively little consideration of factors such as dispersal, carbon sources, herbivory, burial, desiccation, and competition for space or nutrients, indicating directions for future modeling work. In light of this, we present a conceptual framework to help guide future macrophyte growth modelers through a thorough consideration of macrophytes’ myriad interactions with their ecosystems. We also emphasize the importance of modularity and accessibility toward improving efforts to model, and in turn manage, riverine ecosystems.