The effects of nitrogen fertilization and soil properties on mycorrhizal formation of Salix viminalis

The effects of nitrogen fertilization (100, 200 kg N ha(-1) per year) and soil properties on mycorrhizal formation on Salix viminalis were investigated at three short rotation plantations on Gleysols and Cambisols (Abbachhof (ABB) and Wildeshausen (WIL) in Germany. Ultuna (ULT) in Sweden). During 3 years the ectomycorrhizal colonization, the composition of ectomycorrhizal morphotypes and the VAM spore density in the soil were analyzed. The ectomycorrhizal colonization was significantly altered due to N-fertilization at all sites. The quality and magnitude of the fertilization effects on mycorrhizal formation on Salix viminalis varied due to the soil properties, i.e. soil texture, soil N content and pH. The WIL site was characterized by sandy soil (low pH. high soil N content), whereas the ABB site was characterized by clayey soil (high pH, low N content). The ULT site was characterized by clayey soil (high pH. high N content). In the unfertilized control plots (C), ectomycorrhizal colonization was higher at WIL than at ABB. Fertilization reduced the ectomycorrhizal colonization at WIL but increased it at ABB. The distribution of the ectomycorrhizal morphotypes was very heterogeneous within the treatments, therefore significant differences were rare. Sporocarps were collected at ABB during one growing period. The sporocarps were mostly from saprophytic species, with exception of the ectomycorrhizal species Inocybe glabripes. Significant effects of N-fertilization on VAM spore density were observed at two of the three plantations. The pattern in VAM spore density was similar to the pattern seen for ectomycorrhizal colonization. Thus, VAM spore density was increased by fertilization at ABB (low soil N) and decreased at ULT (high soil N). The soil properties have been shown to modify the effects of fertilization on ectomycorrhizal colonization and VAM spore density. Therefore, in management practice of short rotation plantations, the benefit of N-fertilization should be evaluated keeping secondary effects caused by changed mycorrhizal formations in mind, (C) 2002 Elsevier Science B.V. All rights reserved.