Modeling the impact of root exudates and microbes on water and nitrogen uptake using a fully coupled soil plant model

Root architecture and soil-plant interactions affect carbon storage and nutrient uptake efficiency of plants. Mechanistic modeling of the soil-plant system enables a better understanding of coupled processes and allows us to predict the response of the soil-plant system to environmental change.

The fully coupled functional-structural soil-plant model "CPlantBox" can simulate plant growth and soil water flow, solute transport and microbial dynamics. In the rhizosphere, the area influenced by the root activity, focus is put on the influence that special root exudates called mucilage have on the plant water uptake and how the microbial activity promoted by the root exudation impacts the nitrogen uptake.

Both the mucilage and the nitrogen cycling in microbes are investigated using a sensitivity analysis: For a given metric of interest (e.g. total microbial biomass after 10 days of root growth) each parameter gets assigned a measure of importance and of interactions with other parameters. This standard approach of sensitivity analysis is extended to parameter inequalities, enabling the inclusion of additional information.

Through the sensitivity analysis we will be able to identify which model parameters determine the effects of root exudates on microbial N mineralization, plant water and N uptake. Measurements from drought and nitrogen limitation experiments will be used to estimate these important model parameters.