Numerical assessment of the effect of forest structure changes on CO2 flux footprints for the flux tower in Solling, Germany

There are many natural and anthropogenic reasons why a gap can occur inside the forest. When a gap appears within a studied stand (e.g. near a flux tower which operated for some time, providing information about the ecosystem–atmosphere exchange), an assessment of new measurement conditions should be carried out. Using a three-dimensional approach for footprint estimation based on numerical solution of Reynolds-Averaged Navier–Stokes (RANS) equations, we investigated possible changes in air flow and CO2 flux footprints resulting from two suggested forest management activities – clear-cut and stripe-cut – around the flux tower located in 130-year-old spruce forest in the Solling highland, Germany. The model results show that degree of changes in flux footprints depends on the chosen management strategy. The clear-cut strategy produces the largest changes and the stripe-cut leads to weaker changes of investigated characteristics. The role of remote canopy sources increases, while the contribution of remote soil sources decreases with increased share of removed trees. In general, the investigated characteristics change differently for summer and winter due to the combined effects of phenology and upwind topography.

Research highlights▶ The forest management affects the flux footprint of the measuring tower. ▶ The approach based on a 3-D RANS model allows to consider this effect in detail. ▶ Clear-cuts produce stronger effects on fluxes and flux footprints than stripe-cuts. ▶ The spatial distribution of management-induced effect depends on season of the year.