NutsFor a process-oriented model to simulate nutrient and isotope tracer cycling in forest ecosystems

We developed a process-oriented model called NutsFor that simulates nutrient cycling of major cations (Ca, Mg, K, Al, NH₄, Na) and anions (NO₃, SO₄, Cl) and the stable isotope tracers for each of the respective elements at the scale of an ecosystem (isotopic fractionation are not simulated). We tested the ability of NutsFor to reproduce major element and stable isotope tracer (²⁶Mg and ⁴⁴Ca) cycling with the data from 35-yr old beech stand in France. NutsFor correctly reproduced the measured trends in soil solution chemistry for most major elements. The high similarity between modeled and measured distribution of ²⁶Mg and ⁴⁴Ca tracers in the ecosystem provided a unique and robust way to evaluate the hypotheses grounding the model and study the efficiency of Mg and Ca cycling at this very nutrient-poor site.