Microbial enzyme activities under experimental drought and warming at Clocaenog forest and Peaknaze Moor (2012)

Soil cores were collected in July 2012 using a cylinder auger. Three soil samples were taken from the topsoil 0 to 10 centimetres and bulked to one composite sample per experimental plot. Soil samples were kept at 2 to 4 degrees Celsius until enzyme assays were completed. Roots were removed, and soils were sieved to less than 2 millimeters.

Soil enzyme activity of six hydrolytic enzymes was assayed using 4-methylumbelliferone (MUF) or 7-amino-4-methyl coumarin (AMC) linked-substrates. Seven mL of MUF-substrate + 50 mM acetate buffer solution with pH 4.6 were added to 1 gramme of fresh soil. This solution was incubated at 10 degrees Celsius in the dark. Then, soil suspensions were centrifuged for five minutes, and supernatant solutions were measured colorimetrically on 96-well plates at 330 nanometres (nm) and 450 nm (Cary Eclipse Fluorescence Spectrophotometer, Agilent, Santa Clara, CA, USA).

Extracellular phenol oxidase activity was measured 1 gramme of soil in 9 mL of ultra-pure water. Solutions were mixed and diluted with 450 microlitres of ultrapure water. Afterwards, 750 microlitres of 10 mM dihydroxy phenylalanine (L-DOPA) were added, samples were incubated for 9 minutes at 10 degrees Celsius , followed by centrifugation at 10,000 rpm for 5 minutes. Absorbance of the supernatant was measured at 460 nm. Phenol oxidase activity was calculated using Beer-Lambert's Law, with a molar absorption coefficient for the L-DOPA product 3-dihydroindole-5,6-quinone-2-carboxylate (DIQC) of 3.7-104.

Soil water content (percentage) was determined as loss in weight after drying the soils at 105 degrees Celsius for 24 hours. Soil organic matter content (SOM in percent) was determined as difference in weight between soils that were dried at 20 degrees Celsius and 375 degrees Celsius overnight.

Soil nitrate and ammonium were determined in 0.5 molar K2SO4 soil extracts, by standard spectrophotometrical methods. Samples were analysed by autoanalyser (Indol-phenol blue and sulphanilamide/NEDA/Cd/Cu reaction methods respectively). Soil available phosphorus was determined in Mehlich-3 soil extracts, and analyzed using standard spectrophotometrical methods. Water-soluble soil phenolics were determined spectrophotometrically using the Folin-Ciocalteau's reagent. Soil microbial biomass was determined on a paired soil sample extracted with 0.5 M K2SO4 where one sample was fumigated with chloroform. Soil microbial biomass carbon and nitrogen were measured on an autoanalyzer and calculated as difference between carbon and nitrogen concentrations in the none-fumigated and the fumigated samples. A correction factor was applied.

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 Environmental Information Data Centre.

This dataset is included in the following collections

Data from the Climoor climate change experimental fieldsite in Clocaenog forest, UK