SuperSites Data Portal

Soil samples were collected according to the methods described at the BASE dataportal (http://www.bioplatforms.com/sample-collection-procedure). Briefly, nine discrete soil samples from a 25 m x 25 m quadrat, sampled at two depth ranges (0 – 10 cm and 20 – 30 cm). Eight samples were taken at the corners and mid-points of the 25 m x 25 m sides of the quadrat, with sample taken at the centre. The nine subsamples were combined for each depth, to return a single surface and deeper soil sample per quadrat. Samples for chemical and physical analysis were air-dried and transported to CSBP laboratories, Perth, Australia (http://www.csbp-fertilisers.com.au/csbp-lab).

Soil moisture (%GWC) was measured gravimetrically, ammonium and nitrate were determined colorometrically, following extraction with 1M potassium chloride (25˚C). Available phosphorus and potassium were measured using the Colwell method. Sulphur was determined by the Blair/Lefroy Extractable Sulphur method. Organic carbon was determined using the Walkley-Black method. For pH, CaCl pH and electrical conductivity (EC1:5), soils were extracted in deionised water for 1 hour to achieve a soil: solution ratio of 1:5. The water pH and EC1:5 of the extract were subsequently measured using a combination pH electrode. After water pH and EC were measured, calcium chloride solution was added to the soil solution and after thorough mixing the calcium chloride pH determined. Diethylene-triamine-pentaacetic acid (DTPA) trace elements (Cu, Fe, Mn, Zn) were determined by atomic absorption spectroscopy following extraction with (DPTA) for 2 hours. Soils were extracted with a 0.01 M calcium chloride solution and analysed for extractable Aluminium on Inductively Coupled Plasma Spectroscopy (ICP). Boron was measured by ICP after hot CaCl2 extraction. Soil exchangeable cations (Mg, K, Na,Ca) were determined using a 1:5 soil:water extraction. This test was used in combination with the NH4Cl2/ BaCl2 extractable exchangeable cations test, where the value for water soluble exchangeable cations is subtracted from the value for NH4Cl2/ BaCl2 extractable exchangeable cations.

Soil particle size was also measured. Soil were sieved to 2 mm (> 2mm = gravel), treated with hydrogen peroxide to remove the organic matter, then treated with a 1:1 Calgon - Sodium Hydroxide mixture to disperse particles. Using a standardized table of particle sedimentation times, 25ml aliquots were removed from the shaken sample and the remaining sample sieved. The samples were evaporated, oven dried and weighed to determine the sand, silt and clay contents.

Ref: Bissett et al. Introducing BASE - The Biomes of Australian Soil Environments soil microbial diversity database. GigaScience (Submitted)