Ectomycorrhizal sporocarp occurrence as affected by manipulation of litter and humus layers in Scots pine stands of different age

The effects of litter and humus layers on the occurrence of ectomycorrhizal sporocarps in 64 plots in six stands of Pinus sylcestris were studied. In 1990, litter and humus layers and herbaceous vegetation were removed ('sod-cutting') in plots in stands of Pinus sylvestris of different age. Removed litter and humus were added on to existing ectorganic layers ( 'sod-addition') in plots in young and middle-aged stands. Control plots were present. Surveys carried out in 1993 showed that removal of litter and humus layers enhanced numbers of species and sporocarps of ectomycorrhizal fungi. Chemical analyses showed a reduction of the Ndissolved, NH~-, NO 3, P and K + concentrations and an increase of pH of ectorganic layers as a result of sod-cutting. The N concentrations of the needle samples from the Scots pine trees in the sod-cut plots were reduced compared to the control plots. Addition of litter and humus layers did not affect numbers of species and sporocarps of ectomycorrhizal fungi. Numbers of species and sporocarps of ectomycorrhizal fungi on Haplic Arenosol soil were higher than on Haplic Podzol soil. The low nutrient concentrations and organic matter content and high pH of the Haplic Arenosol soil were likely favourable for ectomycorrhizal fungi. The ectomycorrhizal species composition was also affected by the age of the Scots pine trees.