DOI: 10.5285/9bfa5e3b-dbf0-46fc-a5c4-7970b0d850a8
title: Microbial enzyme activities under experimental drought and warming at Clocaenog forest and Peaknaze Moor (2012)

description: This data consist of measurements on soil microbial enzyme activity of six hydrolytic enzymes and related soil measurements from the experimental field sites at Clocaenog forest and Peaknaze. Samples were collected in 2012 from plots subjected to experimental drought and warming as well as untreated control plots. Soil cores were taken for the topsoil 0 to10 centimetres.

Enzymes were measured at the climate change field site Climoor that is located in Clocaenog forest, North East Wales and the Peaknaze field site located in the Peak District. The experimental field sites each consist of three untreated control plots, three plots where the plant canopy air is artificially warmed during night time hours, and three plots where rainfall is excluded from the plots at least during the plants growing season (March to September).

Six hydrolytic soil microbial enzymes and one oxidase were extracted from the topsoil to test the effect of these enzymes that are involved in carbon, nitrogen and phosphorus cycling, under the imposed long-term climate change treatments. The hydrolytic enzymes were assayed using 4-methylumbelliferone (MUF) or 7-amino-4-methyl coumarin (AMC) linked-substrates, whereas the oxidase was extracted in pure water. All enzyme extracts were measured colorimetrically.

The Clocaenog and Peaknaze field experiments intend to answer questions regarding the effects of warming and drought on ecosystem processes. Plot level microbial related measurements are important to investigate ecosystem carbon dynamics and changes in the soil carbon under the imposed climatic treatments.

Measurements were undertaken by trained members of staff at the UK Centre for Ecology & Hydrology.
description: 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.