Ectomycorrhizal activity as affected by soil liming

In this thesis effects of liming on ectomycorrhiza have been studied in relation to effects on root colonization, fungal growth and nutrient uptake. In field experiments the effects of liming on ectomycorrhizal colonization of root tips were variable, possibly due to different soil types and climatic variations. However, a changed mycorrhizal community structure could be detected. Laboratory studies also showed that the substrate may influence the outcome of lime applications. The nutrient status of the substrate had a marked effect on how mycelial growth was affected by liming. Under the experimental conditions used in the studies presented in this thesis, liming reduced the uptake of nitrogen and phosphorus by both mycorrhizal and non-mycorrhizal plants. The amount of extractable nitrogen and phosphorus in the peat was also reduced by liming. The latter could be due to either microbial or chemical immobilization. The lime induced decrease in nitrogen uptake was stronger in non-mycorrhizal plants than in mycorrhizal plants. Thus, the mycorrhizal plants had a higher ability to deal with the negative effects of liming on nitrogen availability than the non-mycorrhizal plants. This was not the case for phosphorus, however. The lime induced decrease in phosphorus uptake was stronger for mycorrhizal plants than non-mycorrhizal plants, and in the highest lime treatment there was no significant difference between the mycorrhizal and the non-mycorrhizal spruce plants.