Provenance & quality
Flux measurements were made using a high-precision closed chamber system where air was circulated between the chamber and an Aerodyne quantum cascade laser instrument measuring mixing ratios at 1 Hz. Fluxes were calculated from the concentration change in each chamber by linear and non-linear regression using the R package HMR which also provided the 95 % confidence interval in dc/dt. Soil samples were collected and frozen to - 18 ˚C within six hours of collection. Analysis of soils was carried out within 2 months of sampling. NH4+ and NO3- was extracted from the soil samples using 50 ml of 1 M KCl solution for 15 g of soil. The mixture was filtered using 2.5 µm filter paper (Fisherbrand, Hampton, New Hampshire, USA) and the solution was stored and frozen in 20 ml plastic vials. Concentrations of NH4+ and NO3- were measured using a Bran and Luebbe AutoAnalyser (SPX Flow Technology, Norderstedt, Germany) by the analytical department at the School of Geosciences, University of Edinburgh. A sub sample of the dried soils was taken to be ground (via ball milling) for elemental analysis of total carbon and nitrogen content of the soil (vario EL cube, Elemaentar, Hanau, Germany), also by the analytical department at the School of Geosciences, University of Edinburgh.