The forest modelling series ForM-S: applications to the Solling spruce site

The forest model series ForM-S currently includes four modules addressing (1) water fluxes (ForHyM), (2) soil temperature (ForSTeM), (3) ion fluxes (ForIoM), and (4) primary production and nutrient cycling in upland forest stands (ForSVA). The modules require climate records (air temperature, precipitation volume), total atmospheric ion deposition and descriptive site information as input. The models are designed to capture the dynamics of the simulated processes at monthly (ForHyM, ForSTeM, ForIoM) and annual scales (ForSVA). ForHyM and ForSTeM have been verified across diverse sites in North America. For the Solling dataset, ForHyM closely reproduced hydrologic data (monthly throughfall, forest-floor percolate, soil percolate) without further calibration. With ForSTeM and ForHyM, snowpack water, soil temperatures, and frost penetration were simulated. ForIoM simulations compared favourably with the concentration and flux data for individual ion species (H+, K+, Na+, NH+4, Cl−, NO−3, Ca2+, Mg2+, SO2−4, Alx+) in throughfall, forest-floor percolate and soil percolate after calibrating one or two parameters for the forest canopy, the forest floor, the mineral soil. Nutrient losses, nutrient uptake rates, base cation replenishment rates within the soil, and biomass production and accumulation for the main stand compartments (foliage, wood, fine roots, forest floor) were simulated with ForSVA. The resulting calculations about cumulative soil leaching losses for Ca, Mg, K, NH4-N, NO3-N, and SO4-S were in good agreement with observations