Modelling the Root Age Structure of Perennial Woody Plants

Document Type


Publication Date



Root age and nutrient uptake efficiency are typically inverse. It has been suggested overall growth is enhanced by maintaining a large population of younger roots while minimizing biomass allocation to older roots which have low efficiency. However, there are trade‐offs in senescing scheduling for new roots and a root age distribution could be skewed towards older roots. Root turnover and root production have been proposed as two methods by which plants control the age distribution of roots. Unfortunately, direct examination of these hypotheses is not experimentally tractable as measuring root age can be difficult. However, an age based theoretical model with varying cost‐benefit ratios for roots of different ages could be used to examine the impact on overall uptake of alternative root age distributions. The ability of this model to analyze how root age distribution affects growth may enhance our capability to project whole‐plant growth. To our knowledge, no such model has been constructed. We apply an integral equation approach, similar to many structure population models, using varying death, survivorship, and cost‐benefit curves to analyze the age distribution of the roots. To simulate growth and aging, we include feedbacks between roots and shoots to incorporate the additional influx of nutrients from roots and carbon from shoots as the plant ages. An objective is to observe the impacts on plant growth of changing root age structure throughout the life cycle and determine conditions for which age distribution dynamics tends towards a steady state, a cycle, or if the age distribution fluctuates.


Presented at the Soil Ecology Society Summit, Fort Collins, CO.