Temperature and moisture alter organic matter composition across soil fractions

• Published in: Geoderma 2022-03, Vol.409 (C), p.115628, Article 115628
• Main Authors: Cates, Anna M., Jilling, Andrea, Tfaily, Malak M., Jackson, Randall D.
• Format: Article
• Language: English
• Subjects: FTICR-MS; Incubation; SOC sequestration; Soil aggregates; Soil organic matter
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2021.115628

[Display omitted] •Soil fractions had distinct SOC profiles, especially silt and clay and coarse POM.•Physical protection of SOC was altered by temperature and moisture.•Simple C was altered by both temperature and moisture.•Complex C was altered by moisture. Understanding the complex interplay of biotic and abiotic controls on soil organic carbon (SOC) stabilization and aggregate formation is a vital and evolving research field, with implications for C and climate change modeling. Here, we delve into the effects of temperature and moisture treatments on aggregate SOC composition. Aggregate fractions representing different levels of physical protection for SOC were isolated three times during a 6-month incubation with 2x2 factorial temperature and moisture treatments (22 or 30 °C, 45% or 65% water-filled pore space). The chemical composition within each fraction was analyzed using high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) to evaluate the prevalence of different classes of C compounds by fraction and temperature and moisture treatments. In addition, a partial least square regression (PLSR) was used to explore potential correlations between relative abundance of C compound classes and C content within aggregate fractions. We found that organic matter in the macro- (>250 µm) and micro-aggregates (53 to 250 µm) was relatively enriched in lipid-, carbohydrates-, and protein--like compounds compared to silt and clay fractions (