Changes in diversity and storage function of ectomycorrhiza and soil organoprofile dynamics after introduction of beech into Scots pine forests

Diversity and storage function of mycorrhiza as well as soil organoprofile formation were investigated in a chronosequence of a pure Scots pine (Pinus sylvestris L.) stand, of Scots pine stands that were underplanted with beech (Fagus sylvatica L.) and in three pure beech stands of different age. Mycorrhiza diversity was higher in the pure beech stands compared to the pure pine stand. Beech and pine trees in the mixed stands had similar dominant mycorrhiza morphotypes. However, trees in two of the three pure beech stands were mycorrhized with other types. Mycorrhizal abundance and nutrient amounts of mycorrhizae associated with beech trees were higher in the mixed and in the pure beech stands compared to pine mycorrhizae indicating that nutrient uptake was higher in older beech than in older pine trees. Humus quality varied from pine to beech stands. Plant litter storage in the humus layer was highest in the youngest mixed stand and lowest in the oldest beech stand. Humus forms changed from moder grass-type in the pure Scots pine stand to mor-like moder and moder rich in fine humus with increasing age of beeches in the mixed stands. The older beech stands were characterised by oligomull and mull-like moder as the dominating humus forms. The ecologically favourable humus forms, i.e., nutrient rich humus forms in the older beech stands correlate well with the higher mycorrhizal diversity and abundance as well as the higher nutrient storage of their mycorrhizae in these stands. The results are also discussed with regard to the 'base-pump effect' of beech trees.