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Abstract Although biological soil crusts (BSCs) are known for a variety of ecological functions, the role of individual biocrust organism species in BSCs on their P cycling is almost unknown. To evaluate the hypothesis that the contribution of defined cultivable taxa of fungi and algea might influence the microbial P storage and mobilization in the underlying soil, a transect was investigated in a glacier foreland in the mountain plateau Hardangervidda in Southern Norway. Microbial biomass P storage in soil under BSC increased continuously with increasing distance to the glacier and increasing fungal species richness. Lowest soil phosphatase activity and soil organic matter content were linked with highest number of algal and fungal in the overlaying BSCs. Enhanced soil microbial biomass P was linked with an increasing water content and decreasing pH CaCl2 of the soil. Nine to 21 algal and 5 to 10 fungal taxa were identified per test site from BSCs along the transect. Members of the Eustigmatophyceae and Xanthophyceae were observed exclusively close to the glacier, those of Klebsormidiophyceae exclusively in larger distance. The most common fungal genera in the BSCs were Lecythophora , Penicillium, Rhizoscyphus and Pholiota, whereas Cosmospora sp., Thelebolus globosus and Mucor hiemalis were found exclusively close to the glacier. The presence of usually biomass-rich taxa in the soil crusts was related to an increased microbial P storage in total. An increasing impact of microbial P storage under BSCs on the subsequent successional vegetation development is suggested. Highlights • Microbial biomass P storage increased continuously with increasing distance to the glacier. • Microbial biomass P storage increased continuously with increasing fungal abundance. • Top-down control of fungi on P mobilization reflected by abundance of dark septate endophytes. [ABSTRACT FROM AUTHOR]

Abstract: Low supply of the nutrients nitrogen (N) and phosphorus (P) limit plant growth and spreading, and increase the plant-microbial nutrient competition in subarctic and arctic regions. We investigated the mycorrhizal community structure of a polar shrub willow (Salix polaris) and the microbial turnover in its rhizosphere to explore the adaptation of a mycorrhizal plant in the subarctic tundra. The ectomycorrhizal colonisation ranged from 35 to 64% of the fine root tips and decreased with an increasing soil C/N ratio. In total, 16 ectomycorrhizal morphotypes were found under S. polaris (eight to 13 morphotypes per site, five morphotypes at all four sites). Cenococcum sp. was the most common EM fungus (32% of the ectomycorrhizal fine roots). The abundance of Cenococcum sp. increased with an increasing organic matter content and N/P ratio in the soil. Arbuscular mycorrhizal colonisation of S. polaris was absent or less than 1% of the fine root length. Microbial biomass P accounted for 21–75% of the organic soil P and 6–49% of the total soil P. Microbial biomass P, alkaline and acid phosphatase activities in the rhizosphere increased with increasing soil N concentration. We conclude that a higher N supply decreases the diversity in the mycorrhizal community on polar willows and increases the role of P turnover from the soil microbial biomass for the nutrient supply. [Copyright &y& Elsevier]

Abstract: The goat willow (Salix caprea) belongs to the typical pioneer vegetation at former ore mining sites in Middle Europe as a result of its high metal-tolerance. Ectomycorrhizal (EM) fungi are known to contribute essentially to the tolerance of plants against abiotic stress. We investigated the EM associations of S. caprea at three former silver-mining sites around Freiberg (Saxonia, Germany) after 33years of revegetation. The EM colonisation ranged from 3 to 36% of the fine root tips. We found 14 different EM types and characterised them morphologically as well as anatomically. The fungal partners were identified using LSU and ITS sequences. They belonged to four families: Thelephoraceae, Cortinariaceae, Tricholomataceae and Tuberaceae. Thelephoraceae, with 53–91%, comprised the largest portion of the total EM colonisation at all test sites and sampling dates. Thelephoraceae produced mainly contact exploration types of ectomycorrhiza. Tricholoma cingulatum was the only EM fungus which was found as ectomycorrhiza and sporocarp. We suppose that the low exploration of the majority of EM associations of S. caprea, in combination with high portions of metal-chelating organic acids containing fungal partners, contributes essentially to the high tolerance of this tree species against high metal concentrations in the soil. [Copyright &y& Elsevier]