Abstract: In forests in Mongolia, tree roots and ectomycorrhizal fungi must survive several months of soil freezing in winter. To investigate the ectomycorrhizal community after winter, we collected fine roots of Scots pine (Pinus sylvestris) and Siberian pine (Pinus sibirica) and associated soil from Nukht forest in the Bogd-Khan National Reserve, Mongolia. Soil samples were collected from frozen soil at the end of April 2016. We determined the ectomycorrhizal community, and on ectomycorrhizal roots tips and in soils determined the potential activity of enzymes involved in the degradation of soil organic matter. In order to assess the temperature sensitivity of enzyme activity, potential soil enzyme activities were assayed at temperatures ranging from 5 to 20 °C. For Pinus sylvestris and Pinus sibirica, a total of 24 different ectomycorrhizal morphotypes could be distinguished; 18 morphotypes could be identified to taxa. The two Pinus species had dissimilar ectomycorrhizal communities, and only 2 ectomycorrhizal fungal taxa were common to both species. Most ectomycorrhizal taxa had measurable activity of at least one extracellular enzyme. A high contribution to the community extracellular enzyme activity was shown for abundant and less abundant taxa. Among the eight tested soil enzymes, only the activity of leucine amino peptidase showed consistent higher Q10 values at 5-15 °C compared to 10-20 °C, suggesting that the enzyme is adapted to colder temperatures. Total soil N was the strongest factor explaining differences in soil enzyme potential activity. A positive relationship was found between soil N and the potential activity of acid phosphatase. We suggest that for both Pinus sibirica and Pinus sylvestris it may be advantageous for nutrient acquisition to have viable ectomycorrhizas during soil thawing in spring.
Keywords: Ectomycorrhizas, enzyme activity, soil freezing, Pinus sibirica, Pinus sylvestris
