Far North Queensland, Soil Chemistry Data, 2019 

The data set contains information on topsoil chemistry for 20, 10 cm deep soil cores sampled along an elevation gradient (40-1550 m a.s.l.) in Far North Queensland. Information on soil C:N, N:P and C:P ratios and soil pH and organic matter content are provided. Soil elemental composition such as calcium, potassium, phosphorus, sulphur, iron, manganese, boron, aluminum, copper, zinc, lead, chromium, and cadmium are also provided. In addition, the data set contains information on soil δ¹³C and δ¹⁵N isotope concentration. 

We at TERN acknowledge the Traditional Owners and Custodians throughout Australia, New Zealand and all nations. We honour their profound connections to land, water, biodiversity and culture and pay our respects to their Elders past, present and emerging. The field work and analytical costs for this project was funded by The Skyrail Rainforest Foundation, The Wet Tropics Management Authority and the Ian Potter Foundation. 

The soil chemistry data was generated as part of the author's PhD project that investigated trends in microclimate and soil chemistry along an elevation gradient in the Australian Wet Tropics World Heritage Area (AWT). This data set was used in conjunction with the FNQ microclimate information Far North Queensland Microclimate Data as part of the author's thesis. 

Soil Sampling survey: Soil nutrients and isotope composition were measured in composite soil samples collected from the study sites (n=20) where microclimate is being monitored in the AWT. At each site, the authors collected five soil cores using an auger (~10 cm deep) after removing leaf litter consisting of recognizable leaf fragments. Samples were bulked and homogenized for each site prior to analysis. Soil pH in H₂O and in 0.01 M CaCl₂ were measured on fresh soil using an ISFET pH pen (Model 24006 DeltaTrak). Samples were then oven-dried at ca 105℃ for up to 72 h and powdered using a Benchtop Ring Mill.

Soil analysis: Total soil elemental analysis was conducted using microwave-assisted acid digestion of the oven dried samples, followed by ionization detection using the Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES) at the Advanced Analytical Centre, JCU - Townsville. Soil carbon (%C) and nitrogen (%N) were measured using a Costech elemental analyser (EA) (Milan, Italy) fitted with a zero-blank auto-sampler at the Advanced Analytical Centre, JCU - Cairns. This was used to calculate the C:N ratio. The stable carbon and nitrogen isotope ratio (expressed as δ¹³C and δ¹⁵N) of the samples was measured using acThermoFinnigan Deltaplus XL isotope ratio mass spectrometer (ThermoFinnigan GmbH, Bremen, FRG), linked to the EA via a ConFlo III interface. Stable isotope results are reported as per mil (‰) deviations from the AIR reference standard scale for δ¹⁵N. Soil organic matter content (OMC) was calculated via loss of mass on ignition (360℃ for 2 h).