DOI: 10.5061/dryad.ncjsxkt20
title: Data from: Fog controls biological cycling of soil phosphorus in the Coastal Cordillera of the Atacama Desert

description: In this study, we collected topsoil samples (0‒10 cm) from each of 54
 subsites, including sites in direct adjacency (&lt; 10 cm) and in 1 m
 distance to plants, along an aridity gradient across the Coastal
 Cordillera in the Atacama Desert. The soluble salts anions (NO3‒,
 Cl‒, and SO42‒) and cations (Ca2+, Na+, Mg2+ and K+) were tested. And we
 performed soil sequential P fractionation and the oxygen isotope values of
 HCl-extractable Pi (δ18OHCl-Pi). 
description: 1) Soil salt ions analysis The soluble salts
 were extracted by Milli-Q water at a soil/water ratio of 1:10. Then the
 anions (NO<sup>3</sup><sup>‒</sup>,
 Cl<sup>‒</sup>, and
 SO<sub>4</sub><sup>2</sup><sup>‒</sup>) concentrations in the extracts were analyzed by ion chromatography (Metrohm IC 850), and those of cations (Ca<sup>2+</sup>, Na<sup>+</sup>, Mg<sup>2+</sup> and K<sup>+</sup>) were determined by Inductively Coupled Plasma Optical spectroscopy (ICP-OES, iCAP 6500). 2) Soil sequential P fraction Sequential P fractionation was performed according to the Hedley sequential fractionation scheme as modified by Tiessen and Moir. In brief, 0.5 g of each air-dried soil sample was sequentially extracted with four reagents including (i) 30 ml deionized water with two anion exchange resin stripes; (ii) 30 mL 0.5 M NaHCO<sub>3</sub> solution at pH 8.5; (iii) 30 mL 0.1 M NaOH; and (iv) 25 mL 1 M HCl. Finally,<em> aqua regia</em> was used at 130 <sup>0</sup>C to extract residual P as chemically most stable P form. After fractionation, the concentration of inorganic P (P<sub>i</sub>) in the extracted solutions was measured by the molybdenum blue colorimetric method and measured at 890 nm by the Photometer Analytik Jena SPECORD 205. Total P (P<sub>t</sub>) was measured by ICP-OES (iCAP 6500), and the difference between P<sub>t</sub> and P<sub>i</sub> was used as organic P (P<sub>o</sub>). 3) Oxygen isotope composition of HCl-extractable P<sub>i</sub> For analysis of the oxygen isotope values of HCl-extractable P<sub>i</sub> (δ<sup>18</sup>O<sub>HCl</sub>-<sub>Pi</sub>), we followed the method presented by Tamburini et al. (2010), which produced organic matter-free silver phosphate (Ag<sub>3</sub>PO<sub>4</sub>) from acid extracts for oxygen analysis. Twenty g air-dried soils were successively extracted by 0.5 M NaHCO<sub>3</sub>, 0.1 M NaOH and 1 M HCl at a 1/10 soil/solution ratio (Amelung et al., 2015). We discarded the alkaline extracts to remove most of the organic P compounds and polyphosphates, so that only the 1M HCl extract was used for further purification process. The phosphate was precipitated as ammonium phosphomolybdate and magnesium ammonium phosphate successively. Cation exchange resin (Dowex 50X8, 200‒400 mesh, Sigma-Aldrich, Darmstadt, Germany) was used to extract all cations from the solutions and finally precipitated as silver phosphate (Ag<sub>3</sub>PO<sub>4</sub>). The Ag<sub>3</sub>PO<sub>4</sub> crystals were dried in an oven at 50 ℃ for a few days and yellow euhedral Ag<sub>3</sub>PO<sub>4</sub> crystals formed after 1 or 2 days. The δ<sup>18</sup>O<sub> </sub>value of Ag<sub>3</sub>PO<sub>4 </sub>was measured at the Plant Nutrition group at ETH Zurich. Each sample was analyzed in duplicates (resulting in a total of <em>n</em>=108) using a Vario PYRO Cube (Elemental, Hanau, Germany) with a C-based reactor coupled in continuous flow to an Isoprime 100 isotope ratio mass spectrometer (Isoprime, Manchester, UK). The furnace was kept at 1450 ℃ and the produced reaction gases were concentrated by a purge and trap chromatography system. Calibration was performed against an internal Ag<sub>3</sub>PO<sub>4</sub> standard (δ<sup>18</sup>O=14.1‰) and two international benzoic acid standards (International Atomic Energy Agency; IAEA 601, δ<sup>18</sup>O=23.1±0.5‰ and IAEA 602, δ<sup>18</sup>O=72.2±0.5‰). All values were reported in the conventional delta notation relative to Vienna Standard Mean Oceanic Water (VSMOW) after calibration.
description: # Fog controls biological cycling of soil phosphorus in the Coastal
 Cordillera of the Atacama Desert DOI: 10.5061/dryad.ncjsxkt20 In this
 study, we collected topsoil samples (0‒10 cm) from each of 54 subsites,
 including sites in direct adjacency (&lt; 10 cm) and in 1 m distance to
 plants, along an aridity gradient across the Coastal Cordillera in the
 Atacama Desert. The soluble salts anions (NO3‒, Cl‒, and SO42‒) and
 cations (Ca2+, Na+, Mg2+ and K+) were tested. And we performed soil
 sequential P fractionation and the oxygen isotope values of
 HCl-extractable Pi (δ18OHCl-Pi). **Description of the data and file
 structure** All the data have been included in the Excel file. The first
 column lists 9 sites along the transect, named as “PAP570, PAP950, PAP870,
 PAP920, PAP1070, PAP1240, PAP1470, PAP1690, PAP2110”. In the second column
 are the 6 subsites in each sampling site along the transect. Following
 that, we have listed the values of δ18OHCl-Pi, Resin P, NaHCO3-Pt,
 NaHCO3-Pi, NaHCO3-Po, NaOH-Pt, NaOH-Pi, NaOH-Po, HCl-Pt, HCl-Pi, HCl-Po,
 Residual-P, and the concentration of Cl‒, NO3‒, SO42‒, Ca2+, Na+, Mg2+ and
 K+ in soils. **Sharing/Access information** This is the raw data obtained
 from the lab work and has no other sources.