Demographic equilibrium modelling of single tree selection stands in Siljansfors : judging the sustainability of single tree selection systems in Sweden

Abstract: Lately debates have occurred questioning the rotation system, which is the most used silvicultural system in Sweden. Continuous cover forestry (CCF) has therefore been suggested as an alternative management method, due to its environmental benefits such as increased biodiversity and higher resilience against extreme weather which is important with the current climate change. One CCF method in particular is the single tree selection system, which depends on a complex forest structure in order to sustainably yield economic and ecological values over time. Experience and knowledge of the dynamics of forest stands managed with the single tree selection system in Sweden are insufficient. One way to increase the understanding of stand dynamics in single tree selection systems is by using demographic models. This thesis aimed to examine the sustainability of single tree selection systems in Sweden, using a dynamic demographic equilibrium model called the Schütz model. Additionally, this dynamic model was translated to the simpler de Liocourt (q-factor) model to facilitate practical use. Based on the models, adapted management suggestions and a judgement of sustainability were made. The results shows that the Swedish selection forest grows slower compared to other selection forest in Europe and have a relative high mortality. Thus, a high rate of regeneration is needed, and the target diameter was limited to smaller diameters than seen in more southern latitudes. However, when comparing the observed diameter distribution of the stands with the model outcome it was seen that well adapted management is crucial for stand development. Furthermore, this comparison suggests that the selection stands can reach their equilibrium. In conclusion, it is possible to sustainably manage forests in Sweden using the single tree selection system. This thesis also suggests that both dynamic and static models can be relied on when making stand evaluations in Swedish forests.