Fig. 1
Principal components analysis using the molecular composition of water-soluble organic carbon collected from different pore size suction domains. A principal components analysis (PCA) of Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry defined organic carbon compound classes (lipids, unsaturated hydrocarbons, lignin, proteins, and so on) for soil pore water collected at a −1.5 kPa suction representing coarse-sized pores and pore-throats (approx. >300 μm diameter), b −1.5 kPa suction representing medium-sized pores and pore-throats (approx. 20–300 μm diameter), and c −50 kPa suction representing fine pores and pore-throats (approx. 6–20 μm diameter) collected from soil cores subjected to antecedent drought or maintained at field moisture conditions and to different rewetting directions (rewet from the top to simulate precipitation wetting, or from below to simulate capillary-led groundwater rise) in the laboratory. Blue shaded points and solid-shaded 90% confidence interval ellipse represent pore water collected from soil cores subjected to field moisture and precipitation-led rewetting conditions (n = 8, 8, and 7 for −1.5, −15, and −50 kPa pore water fractions, respectively), whereas open blue circles and pattern-filled confidence intervals represent field moisture core rewet from below to simulate groundwater rise (n = 8, 8, and 7). Brown shaded points and the corresponding solid-shaded 90% confidence interval ellipse represent pore water collected from soil cores subjected to antecedent drought and rewet via simulated precipitation (n = 8, 6, and 7), whereas open brown circles and pattern-filled confidence intervals represent data from drought-conditioned samples rewet via simulated groundwater rise (n = 7, 6, and 5). Correlation coefficients associated with the PCA are included in Supplementary Table 1
