C and N-isotope and elemental analysis
C and N isotopic signatures (δ13C and δ15N, respectively) and C and N contents of dry samples of moss tissues (ca. 5 mg) were analyzed via conversion to CO2 and N2 by combustion and quantification by mass spectrometry (Werner et al ., 1999), using a DeltaV isotope ratio mass spectrometer (Thermo Fisher Scientific, Bremen, Germany). The data were corrected for drift and non-linear sample size effects. For quantification, we used laboratory standards consisting of wheat and maize flours calibrated against certified reference standards: cyclohexanone, nicotinamide, and sucrose for C; atropine, cellulose, and NIST 1515 apple leaves for N; IAEA-600, IAEA-CH-6, and USGS40 for δ13C; and IAEA-600, IAEA-N-2, USGS40, and USGS41 for δ15N.