Towards understanding tree root profiles: simulating hydrologically optimal strategies for root distribution

摘要

In this modelling studydifferences in vertical root distributions measured in four contrasting forestlocations in the Netherlands were investigated. Rootdistributions are seen as a reflection of the plant’s optimisation strategy,based on hydrological grounds. The "optimal" rootdistribution is defined as the one that maximises the water uptake from the rootzone over a period of ten years. The optimal root distributionsof four forest locations with completely different soil physical characteristicsare calculated using the soil hydrological model SWIF. Twodifferent model configurations for root interactions were tested: the standardmodel configuration in which one single root profile wasused (SWIF-NC), and a model configuration in which two root profiles compete forthe same available water (SWIF-C). The root profiles wereparameterised with genetic algorithms. The fitness of a certain root profile wasdefined as the amount of water uptake over a simulationperiod of ten years. The root profiles of SWIF-C were optimised using anevolutionary game. The results showed clear differences inoptimal root distributions between the various sites and also between the twomodel configurations. Optimisation with SWIF-C resulted in rootprofiles that were easier to interpret in terms of feasible biologicalstrategies. Preferential water uptake in wetter soil regions was an importantfactor for interpretation of the simulated root distributions. As the optimisedroot profiles still showed differences with measured profiles,this analysis is presented, not as the final solution for explaining differencesin root profiles of vegetation but as a first step using an optimisationtheory to increase understanding of the root profiles of trees. style="line-height: 20px;">Keywords: forest hydrology, optimisation, roots