Effect of Land Use Change on Molecular Composition and Concentration of Organic Matter in an Oxisol

Abstract

Land use change from native vegetation to cropping can significantly affect the quantity and quality of soil organic matter (SOM). However, it remains unclear how the chemical composition of SOM is affected by such changes. This study employed a sequential chemical extraction to partition SOM from an Oxisol into several distinct fractions: water-soluble fractions (ultrapure water (W)), organometal complexes (sodium pyrophosphate (PP)), short-range ordered (SRO) oxides (hydroxylamine-HCl (HH)), and well-crystalline oxides (dithionite-HCl (DH)). Coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), the impact of land use change on the molecular composition of different OM fractions was investigated. Greater amounts of OM were observed in the PP and HH fractions compared to other fractions, highlighting their importance in SOM stabilization. The composition of different OM fractions varied based on extracted phases, with lignin-like and tannin-like compounds being prevalent in the PP and HH fractions, while aliphatic-like compounds dominated in the DH fraction. Despite changes in the concentration of each OM fraction from native vegetation to cropping, there was little influence of land use change on the molecular composition of OM associated with different mineral phases. No significant selective loss or preservation of organic carbon compounds was observed, indicating the composition of SOM remained unchanged.

Correspondence on “Effect of Land Use Change on Molecular Composition and Concentration of Organic Matter in an Oxisol”

“…Yang et al recently published an article in Environmental Science & Technology titled “Effect of Land Use Change on Molecular Composition and Concentration of Organic Matter in an Oxisol” . In this study, Yang et al employed a sequential chemical extraction to separate soil organic matter (SOM) from an Oxisol into several distinct fractions: water-soluble fractions [ultrapure water (W)], organometal complexes [sodium pyrophosphate (PP)], short-range ordered (SRO) oxides [hydroxylamine-HCl (HH)], and well-crystalline oxides [dithionite-HCl (DH)].…”

Rebuttal to Correspondence on “Effect of Land Use Change on Molecular Composition and Concentration of Organic Matter in an Oxisol”

“…We value the comments made by Lv and Cao on our recently published article on the effect of land use change on the molecular composition of organic matter (OM) and soil organic carbon (SOC) concentration for an Oxisol. We reported that land use change from native vegetation to cropping resulted in a decrease in OC concentration and had minor effects on the molecular composition of OM.…”