A canonical model of tree resource allocation after defoliation and bud consumption

This paper presents a model of resource allocation in mountain birch (Betula pubescens ssp. czerepanovii (Orlova) Hنmet-Ahti), and uses the model to simulate tree responses to defoliation and bud consumption. The model simulates growth of mountain birch individuals that renew by basal sprouting after being severely attacked by geometrid larvae. The model was constructed by using a canonical approach that takes into account only qualitative information on the processes that govern plant growth. Although the model was parameterised with data from intact trees, it reproduced qualitatively correct and quantitatively reasonable numerical responses to different types of herbivory. In general, the responses were in good agreement with experimental field results, although some of the long-term responses could not be verified due to lack of appropriate data. This study demonstrated that, if sufficient qualitative information is available, canonical modelling can be used to successfully simulate tree functioning in a mechanistic way even though the physiological processes behind the yearly nitrogen budgets and shoot numbers of whole trees are not explicitly included in the model.