Changes in soil dissolved organic matter optical properties during peatland succession

Dissolved organic matter (DOM) is the most active component in the soil environment. Understanding the chemical diversity of DOM and the interaction of the physicochemical properties of the soil are key to managing peatland under succession. In this study, we aimed to understand the effects of peatland succession on soil DOM. We collected soil samples (topsoil: 0-10 cm, subsoil: 10-20 cm) from peatland during different stages of peatland succession in mid-high latitude northern regions, determined the changes in quantity and quality of DOM using fluorescence spectroscopy and parallel factor analysis. We found that peatland succession altered the effec-tiveness of soil nutrients and water content. During the succession, the content of humus-like substances in the DOM of the topsoil increased and the content of protein-like material decreased, whereas the content of sub-stances in the subsoil remained stable. pH was the key factor affecting the change in the composition of the DOM in the topsoil during peatland succession. The variation of DOM in the subsoil may be related to the vegetation composition. The results suggest that fluorescent DOM components respond significantly to changes in peatland succession, and DOM properties are driven by soil pH and vegetation composition during peatland succession. In conclusion, our results reveal the optical changes and factors that influence DOM in peatlands under succession. This suggests that DOM can be modified by simultaneous changes of the physicochemical properties in the soil and the vegetation cover.