Application of Minimalist Mechanistic Nutrient Uptake Models to Woody Plants, Have We Learned Anything Useful?.

Minimalist mechanistic nutrient uptake models derived from the seminal works of Barber, Baldwin, Nye, and Tinker have evolved over the past four decades into useful research tools that seek to encapsulate the fundamentals of nutrient movement in the soil, nutrient uptake kinetics, and root growth and morphology.  Mechanistic models provide a means to evaluate the validity of underlying concepts of soil supply and nutrient uptake as well as test the adequacy of data sets developed to verify model predictions.  Application of these models to woody rather than typical crop species has proven more problematic than initially thought due in part to increased root system complexity, mycorrhizal influences, and lower soil nutrient availability. A lack of agreement between observed and modeled response, while discomforting, does not necessarily imply that the model is wrong. Instead, it should challenge us to verify our understanding of key physical, chemical, and biological processes while at the same time improving the methods we use to measure and describe these parameters. To this end, sensitivity analyses and examples of model predictions associated with soil supply parameters, root uptake, and root growth will be explored along with recent methodology developments and model configurations.  And suggestions for future research will be proposed. In the final analysis, future improvements in methodology and models are most likely to be brought about by close collaborations between experimentalists and modelers.