Modeling soil functions of forested ecosystems

Forests deliver essential ecosystem services that can be impacted by climate, land use and above ground biodiversity changes. Assessment of such impacts can be achieved through ecosystem modeling of interlinked above- and below-ground processes. In this study, the one-dimensional Integrated Critical Zone (1D-ICZ) model was used to simulate the soil functions of two mature forested ecosystems: Zöbelboden in Austria and Hyytiälä in Finland. Both are long-term ecosystem research (LTER) sites with extensive monitoring data. The model was initialized and calibrated using long-term observations and simulated the gross primary production (GPP), the total soil C stock and the concentrations of several components of soil chemistry. The C and N content of Zöbelboden soils (82.55 tC/ha and 3.76 tN/ha) are higher than Hyytiälä (38.61 tC/ha and 1.33 tN/ha) reflecting higher particulate organic matter (POM) accumulation. Temperature and light were found to be the primary limiting factors of plant growth in both sites, and precipitation a limiting factor only at Hyytiälä. Regarding the quantification of soil functions at Zöbelboden, GPP was 15.6 tC/ha/yr, soil C stock 82.6 tC/ha, N stock 3.8 tN/ha and soil CO₂ flux 0.04 tC/ha/yr while for Hyytiala, GPP was 11.6 tC/ha/yr, soil C stock 38.6 tC/ha, N stock 1.3 tN/ha and soil CO₂ flux 0.03 tC/ha/yr. The model can be used to understand the limitations of plant growth and carbon sequestration, processes significant to climate mitigation.