Soil organic matter formation is controlled by the chemistry and bioavailability of organic carbon inputs across different land uses

Soil organic matter and geochemical characteristics shape microbial community composition and structure across different land uses in an Australian wet tropical catchment

“…However, in this study, no significant correlation was observed between labile (O-alkyl C) and recalcitrant (alkyl C) forms of OC and soil microbial communities, which was due to the similarity of SOC functional groups across land uses. This is consistent with the previous study showing that the formation and stabilization of SOM lead to similar proportions of labile and recalcitrant OC functional groups in soils across land uses (Bahadori et al, 2021).…”

“…13 C chemical shifts were referenced relative to external hexamethylbenzene (HMB; δ CH3 , 17.4 ppm). To quantify different OC functional groups, the following chemical shift boundaries were selected for the 13 C NMR spectra (Bahadori et al, 2021; Prietzel et al, 2018). The alkyl C and O‐alkyl C functional groups were within the chemical shift regions 0–45 ppm and 45–110 ppm, respectively.…”

“…Solid-state 13 C cross polarisation magic angle spinning nuclear magnetic resonance ( 13 C CPMAS NMR) spectroscopy was used to determine soil OC functional groups. Soils were pre-treated with hydrofluoric acid (HF) prior to solid-state 13 C NMR analysis to remove paramagnetic species (e.g., Fe 3+ and Mn 2+ ), minimizing their impacts on NMR spectra and concentrating the OM of the whole soil (Bahadori et al, 2021). The 13 C NMR spectra of soils were acquired using a 300 MHz Varian VNMRS spectrometer (Varian Inc., CA) operating at a frequency of 75.4 MHz.…”

“…13 C chemical shifts were referenced relative to external hexamethylbenzene (HMB; δ CH3 , 17.4 ppm). To quantify different OC functional groups, the following chemical shift boundaries were selected for the 13 C NMR spectra (Bahadori et al, 2021;Prietzel et al, 2018) For measuring microbial biomass C and N (MBC and MBN), the chloroform fumigation extraction method was used (Brookes et al, 1985). Briefly, 10 g fresh weight of fumigated and non-fumigated soils were extracted by 40 mL of 0.5 M K 2 SO 4 (soil:extractant ratio of 1:4).…”

“…Such fast‐growing microorganisms can maximise their growth when their favourite resources are abundant, while other microorganisms utilise recalcitrant OC (e.g., alkyl C) and their relative abundance may increase when labile OC resources are limited (Fontaine et al, 2003). Despite the recent studies on variations in soil OC functional groups (Bahadori et al, 2021) and microbial community structure (Guo et al, 2020) across different land uses, only a few studies have investigated the interactions between these two areas (Ling et al, 2021; Ng et al, 2014).…”