Evaluation of the LandscapeDNDC model for drained peatland forest managements, LDNDC v1.35.2 (revision 11434)

Abstract. Rotational forestry (RF) is the prevailing management practice on drained peatlands in Finland, while continuous cover forestry (CCF) is increasingly studied for its potential climate benefits. We applied the process-based LandscapeDNDC model, for the first time, to simulate experimental peatland forest stands under three different managements: RF, CCF and non-managed control. Mixed-species stands of pine, spruce, and birch were initialized, with management, partial harvest of pine in CCF and clear-cut harvest of all species in RF, leading to species shifts toward spruce–birch dominance in CCF and birch seedlings in RF. The primary objective of this study was to evaluate the performance of LandscapeDNDC model in forested drained peatlands. To this aim, we quantified the differences in gas exchange and water balance originating from differences in species composition and management methods. We also implemented modification to dynamic water table (WT) calculations and improved humus pool partitioning based on soil carbon-to-nitrogen ratios. Model evaluation against field data showed strong agreement for daily net ecosystem exchange (correlation 0.84–0.88; Nash–Sutcliffe efficiency 0.66–0.75). Modeled leaf area index (LAI) closely matched site estimates before management and Sentinel-2 satellite estimated LAI afterwards. Soil moisture and WT dynamics were realistically reproduced. Methane flux patterns were accurately captured in the control and CCF stands. Moreover, the methane flux was found to be sensitive to the WT after clear-cut in the RF stand. Modeled annual carbon balances were consistent with measurements and indicated that CCF became a carbon sink more rapidly than RF. These results demonstrate that LandscapeDNDC can reliably simulate the biogeochemical and hydrological consequences of alternative peatland forest management scenarios. The model therefore provides a valuable tool for developing climate-smart management strategies on drained peat soils.