The main goal of the project is to develop new silvicultural strategies by identifying site-specific optimal mixtures of pedunculate oak (Quercus robur L.) and Norway spruce (Picea abies (L.) Karst.), the most common commercial and semi-natural oak forest type in southern Sweden.
We hypothesize that an admixture of spruce may favour the growth of oak during climatically extreme periods, thereby improving forest stability, forest growth, the short- and long-term economic potential of oak for timber production and, in turn, the sustainability of forest management in southern Sweden. We also hypothesize that the optimal share of spruce will be site-dependent.
The project will include three major research themes:
1. An analysis of productivity in pure and mixed stands of oak and spruce in southern Sweden as a function of bioclimatic factors, site type, stocking density, and mixing proportions.
2. A quantification of the response of mixed vs. pure stands in relation to past climatic variability, including natural disturbance factors such as droughts, episodes of strong wind, and infections by pests and pathogens. Specifically, we hypothesize that mixing of oak and spruce in southern Sweden should (a) improve stand resilience to drought-related declines in stand productivity due to spruce-induced decrease in the depth of the soil water table, and (b) provide more even extraction of wood volume / biomass over time (as compared to pure stands of either species), making mixed stands of oak and spruce a commercially attractive option for forest owners.
3. Development of new silvicultural guidelines for mixed stands of oak and spruce, taking into account site-specific productivity, resilience and biodiversity goals under different climatic settings and management priorities.
The project is currently funded by Partnerskap Alnarp.
Igor Drobyshev, igor.drobyshev(at)slu.se & Jens Peter Skovsgaard, jps(at)slu.se