Soil respiration responses to carbon, nitrogen and phosphorous additions to topsoil and subsoil cores from the Conwy catchment in North Wales (2014)

Soil cores were taken from the topsoil 0-15 cm using a soil corer with a diameter of 5 cm for the initial experiment; intact soil cores were collected in winter 2014 using a Van Walt percussion (Cobra TT) core. Soil cores were taken to a depth of 1 metre and topsoil (0-15 cm) and subsoil (85-100 cm) cores were used.

Soil cores were kept in water tight plastic bags to prevent water loss via transpiration at 4 oC till they were adjusted to their field capacity by adding an artificial rain solution. Carbon, nitrogen and phosphorus were added in varying amounts and the result informed the nutrient additions in the main experiment. Carbon was added either as glucose only, a mix of carbon compounds simulating rhizodepsition and as glycine. Nitrogen was added as NH4NO3-N and phosphorus as KH2PO4. In the main experiment, carbon, nitrogen and phosphorus were added in a full factorial design to topsoil and deep soil cores on three consecutive days. Therefore, soils were incubated for 1 or 2 hours (bogs only) at 10 degrees Celsius , gas samples were taken and Carbon Dioxide (CO2) and Nitrous Oxide (N2O) concentrations were measured respectively. Similar incubations were carried further nutrient additions at days 4, 5, 6, 8 10 and 12.

CO2 concentrations were measured using gas chromatography (GC, Perkin Elmer Clarus 500 gas chromatograph, Waltham, MA) equipped with a Porapak QS (80e100 mesh, company, country) analytical column. CO2 standard gases with CO2 concentrations of 250, 500 and 1000 parts per million (ppm) were used to calculated CO2 concentrations in the samples. N2O and CO2 concentrations were measured simultaneously. N2O fluxes were quantified using standards at 5, 10 and 15 ppm.

Nitrogen mineralization was measured 4 weeks after flushing off soil available nitrogen by leaching the soil cores with the artificial rain solution for 4-5 days for soil cores of the main experiment. Soil cores were incubated at 10 degrees Celsius for further 2 weeks after the nutrient addition experiment. To avoid water loss from the cores, cores were stored in breathable plastic bags. After the 4 weeks of incubation, each soil core was sieved (2 mm) and 10 grams moist soil was extracted with 100 mL 1 M KCl. The extract was then analysed for nitrate and ammonium contents (SEAL AQ2+ Discrete Analyser). The total soil dry weight (g) was measured after drying the soil at 65 degrees Celsius and the soil organic matter content was determined gravimetrically by measuring mass loss at 375 degrees Celsius after removal of stones and coarse roots. Soil nitrate, soil ammonium and total nitrogen mineralization rates were calculated as grams per dry weight and grams per organic matter content.

All results were entered into Excel spreadsheets. Results from all the analyses were combined into one Excel spreadsheet. Data were then exported from this combined Excel spreadsheet as .csv files for ingestion into the EIDC.

This dataset is included in the following collections

The Macronutrients Turf2Surf project - The multi-scale response of water quality, biodiversity and carbon sequestration to coupled macronutrient cycling from source to sea