Application of BIOME-BGC model to managed forests: 2. Comparison with long-term observations of stand production for major tree species

In this paper, we applied the process model BIOME-BGC that was adapted to include forest management routines, to managed stands with a long-term observation of biomass production. The exercise includes a model analysis for 33 stands exemplifying typical forest management of beech, oak, pine and spruce, i.e., the four major tree species important to Central-European forestry. The model analysis also included soil carbon component, which was verified using additional independent data collected from 180 forest locations. The paper builds on our companion paper that presented the sensitivity analysis and identified the key ecosystem and site parameters. The adapted model was applied to forest stands modifying only two parameters reflecting site class, namely soil depth and natural nitrogen fixation, while all other parameters were held constant across the stand sites of given species type. In this way the applied model matched the observed long-term biomass development of different stands and species with a mean relative error of 8.2%, ranging from 6.6 to 8.8% for individual tree species. The modeled litter and soil carbon pool was in line with the independent observations available at the level of species groups. Both soil depth and natural nitrogen fixation showed species-specific linear trends with site class that could potentially be utilized for simpler model application on a large scale.