Modelling the yields of marketed mushrooms in Picea abies stands in eastern Finland

•The highest yields of Boletus edulis were obtained before the first thinning phase.•The peak for Lactarius spp. was slightly later.•Warm pre-season and wet conditions during the fruiting season promoted the yields.•The production of Boletus edulis and timber were not competing with each other.

Wild mushrooms are gaining more popularity among consumers. Commercial picking of mushrooms has increased in Finland, which can have an effect on forest management. Currently, mushrooms are considered a side-product of forestry, but understanding the factors affecting the variation in yields would enable the joint production of timber and mushrooms. This study aims to provide empirical models for predicting the annual yields of marketed mushrooms in planted Norway spruce (Picea abies) stands in eastern Finland. Separate models were fitted for Boletus edulis, Lactarius spp. and all marketed mushrooms. Mushroom data were inventoried from 56 sample plots for the period 2010–2014. Stand and annual climatic variables were used as predictors in the modelling. A non-linear mixed-effect modelling (NLMM) approach was used to account for between-plot and between-year variation in mushroom yields. The highest yields of B. edulis were obtained just before the first thinning phase of stand development (at the age of 25–30 years and the stand density of 25 m2/ha). The peak in the yields of Lactarius spp. and all marketed mushrooms was slightly later. The mushroom yields were promoted by a warm pre-season (in July) and wet conditions during the fruiting season (in August). In a good mushroom stand, the contribution of mushrooms to the total net present income (with a 3% interest rate) during the entire rotation was 25%. The results of this study enable the prediction of mushroom yields along with the development of spruce stands and thus support multiple-use planning and management of forests.