Colloidal nutrient transport in a forest ecosystem – from experiment to prediction

Forest stand-replacing disturbances, whether natural or anthropogenic, can transform forests from carbon sinks to sources, impacting soil water content, structure, and nutrient dynamics. While nutrient cycling in forests is extensively studied, there is a notable gap in understanding the contribution of colloidal transport, particularly in temperate forest ecosystems.
This project addresses this gap by proposing a holistic ecosystem model that integrates water and nutrient fluxes, carbon, nitrogen, and phosphorus storage and release, and forest growth. The model extends the AgroC model to simulate forest stands. Calibration and validation will be performed using data from the TERENO site Wüstebach, including measurements of plant diversity, growth, CO2 fluxes, and soil respiration.
To assess colloidal nutrient transport, the HYDRUS-1D software package will be employed, focusing on natural colloids under changing soil water conditions. The lack of understanding regarding the processes and transport pathways of natural soil colloids is addressed through controlled experiments, aiming to identify source strength and estimate colloid-facilitated nutrient transport.
The proposed approach aims to fill critical knowledge gaps in forest ecosystem modeling, particularly in understanding the long-term consequences of major disturbances. By incorporating colloidal transport into numerical models, the study seeks to enhance predictions of elemental fluxes, especially for phosphorus, and improve the overall sustainability and resilience of ecosystems. The research contributes to advancing the understanding of biogeochemical cycles in forests, emphasizing the need for comprehensive models that capture the complexity of ecosystem responses to environmental changes.