Data for mycorrhizal C/N ratio determines plant-derived carbon and nitrogen allocation to symbiosis

Nutrient cycling in temperate forests is driven by carbon allocation of trees to soil via ectomycorrhizas (EM). The sink activities of different fungal taxa for host resources are unknown. Aboveground dual labeling of young beech with 15N and 13C was used to trace resource transport to ectomycorrhizal root tips. Isotope enrichment in EM correlated with that in the corresponding EM-attached lateral root, supporting that EM drive taxon-specific N- and C-fluxes. The enrichments with 13C and 15N in EM increased with decreasing C/N ratio of the symbiotic association.  Abundances of EM species were positively correlated with 13C enrichment, demonstrating higher fitness of stronger than of less C-demanding symbioses. Overall, our results imply that differences among the resource traits of EM species regulate the supply of the symbioses with host-derived C and N.
Here we provide the data sets containing information on the identities of fungal species colonizing roots tips of European beech and ..., Young, healthy beech (Fagus sylvatica) trees (n = 40) with fully open leaves were excavated in May in a beech forest. The trees were carefully removed and placed with intact soil layers individually in pots (diameter: 183 mm, height 255 mm, corresponding to about 6.5 L soil volume) and were kept under common garden conditions in Göttingen until labelling. Three adjacent top, three middle and three bottom leaves were slightly abraded and exposed for 3 days to 15NH4Cl (99% NH4Cl, Campro Scientific GmbH, Berlin, Germany). The labelled leaves were removed and the plants were exposed in gas-tight chambers for two days to 12CO2, then for three days to 13CO2 and then for two days to 12CO2.  The experimental exposures were conducted in two independent runs, each with ten trees. Ten non-labelled trees were used as controls.
Harvests took place immediately after removal and 15 days after removal of the trees from the chambers, corresponding to 5 and 20 days since the start of the 13CO2 treatment...., , # Data for mycorrhizal C/N ratio determines plant-derived carbon and nitrogen allocation to symbiosis

**Table 1 (Table_1_repository): Ectomycorrhizas detected on root tips of Fagus sylvatica.** Columns indicate species hypothesis (based on >97% sequence identities), accession numbers under which the sequences were deposited in NCBI, abbreviations and species numbers used in Table 2. Blast information obtained from NCBI and UNITE is also shown. Abundance (%) per fungal species on day 5 and day 20 after the start of the experiment. The table is useful for diversity studies. It is not required for quantitative analyses. The ectomycorrhizal fungal sequences were searched in two open databases (National Center for Biotechnology Information (NCBI) using nucleotide BLAST () and UNITE using “run analysis” (), which is also based on the BLAST algorithm. Further explanations regarding the column heading for the molecular identification can be found under:

**Table 2 (Table_2_repository) : ...