Modelling soil nitrogen: the MAGIC model with nitrogen retention linked to carbon turnover using decomposer dynamics

Area of Science:

• Environmental Science
• Biogeochemistry
• Ecosystem Modeling

Background:

• Acidification models are crucial for understanding ecosystem responses to pollution.
• Existing models struggle to accurately link nitrogen cycling to carbon turnover in soils.
• Nitrogen (N) saturation dynamics are complex and not fully captured by current models.

Purpose of the Study:

• To introduce a novel formulation of the MAGIC acidification model incorporating decomposer dynamics.
• To link nitrogen (N) cycling with soil carbon (C) turnover.
• To evaluate the enhanced model using long-term water chemistry data from Czech coniferous forests.

Main Methods:

• Developed a new MAGIC model formulation with integrated decomposer dynamics.
• Applied the model to 15-30 years of water chemistry data from three forest sites.
• Analyzed changes in sulphur (S) and N deposition alongside sulfate and nitrate concentrations.

Main Results:

• Sulphate concentrations decreased in line with reduced sulphur deposition.
• Nitrate concentrations declined more significantly than predicted by N deposition alone, challenging existing N saturation models.
• The new model formulation accurately simulated short-term nitrate leaching and long-term N retention.

Conclusions:

• The enhanced MAGIC model provides a more accurate representation of N cycling and soil C turnover.
• Progressive N saturation poses a future risk of increased nitrate leaching and ecosystem eutrophication, even with reduced deposition.
• The study highlights the potential for re-acidification despite observed recovery trends.