An ecophysiological approach to modelling resource fluxes in competing plants

A conceptual model of resource acquisition and allocation within ageneralized, individual plant growing vegetatively in competition withothers is presented. The model considers C and N acquisition, synthesis ofassimilates and their transport and partitioning, growth of new tissues,reserve formation and recycling, and losses due to root exudation andrespiration. These processes are regulated by the relative size of the Cand N substrate pools in shoot and roots, in relation to meristematic sinkstrength. Translocation and allocation patterns are represented accordingto the Minchin phloem transport model. The current model is used toconsider the impact of competition on resource acquisition and allocation,first by considering a plant growing in isolation and its response tomanipulation of light, CO2 and N supplies. Secondly, competitive plants areintroduced and the direct effects on plant responses in terms of resourcedepletion are considered separately from indirect effects such as potentialchanges in the quality of resources available (e.g. light quality or soil Nsources). In the past, many studies of plant competition have notestablished the importance of these indirect effects because they have notestablished all the processes involved in competition. This model can beused to interpret responses of whole plants to their neighbours in terms ofthe relative importance of both the direct and indirect effects ofcompetition.