Immediate effect of thinning on the yield of Lactarius group deliciosus in Pinus pinaster forests in Northeastern Spain

► We quantify the influence of different thinning intensities on Lactarius yield. ► The results are based on an experimental design with thinned and control plots. ► Thinning has an immediate and sharp effect on Lactarius yield. ► The thinned (removed) basal area has stronger effect than the remaining basal area. ► Late-summer rainfall is the main environmental factor affecting Lactarius yield. Picking forest mushrooms is an increasingly valued leisure time activity in many regions of the world. In Northeastern Spain edible mushrooms such as Lactarius deliciosus (saffron milk caps) are highly appreciated, stimulating interest in the multiple factors that influence their production. Topographic factors (altitude, slope and aspect), weather conditions and stand characteristics (tree species, stand density and tree age) are the main factors influencing mushroom production. Of these, only stand characteristics can be modified by means of forest management. The objective of the present work is to assess the influence of thinning on the production of Lactarius delicious group sporocarps in an even-aged Pinus pinaster forest in Northeastern Spain. A total of 30 plots with a basal area reduction ranging from 0% to 77% were established in 2008 and monitored during the autumn mushroom seasons of 2009 and 2010. Fifteen non-thinned plots were also surveyed in 2008. The results show a clear positive response of saffron milk cap production to forest thinning. Production was five times greater in plots in the first year after thinning and two times greater in the second year, as compared to the non-thinned plots. Thinning intensity and precipitation during August and September were the most significant factors explaining the annual yield of Lactarius group deliciosus sporocarps.