Tree biomass in the Swiss landscape: nationwide modelling for improved accounting for forest and non-forest trees

Trees outside forest (TOF) can perform a variety of social, economic and ecological functions including carbon sequestration. However, detailed quantification of tree biomassis usually limited to forest areas. Taking advantage of structural information available from stereo aerial imagery and airborne laser scanning (ALS), this research models tree biomassusing national forest inventorydata and linear least-squareregression and applies the model both inside and outside of forest to create a nationwide model for tree biomass(above ground and below ground). Validation of the tree biomassmodel against TOF data within settlement areas shows relatively low model performance (R 2 of 0.44) but still a considerable improvement on current biomassestimates used for greenhouse gas inventoryand carbon accounting. We demonstrate an efficient and easily implementable approach to modelling tree biomassacross a large heterogeneous nationwide area. The model offers significant opportunity for improved estimates on land use combination categories (CC) where tree biomasshas either not been included or only roughly estimated until now. The ALS biomassmodel also offers the advantage of providing greater spatial resolution and greater within CC spatial variability compared to the current nationwide estimates.