Land-Use Change and Environmental Properties Alter the Quantity and Molecular Composition of Soil-Derived Dissolved Organic Matter
Huan Tong, André J. Simpson, Eldor A. Paul, Myrna J. Simpson
Abstract
Dissolved organic matter (DOM) is a major pool of actively cycling organic carbon in soils, and can be exported to aquatic environments. The quantity and chemistry of DOM vary with different environmental factors, such as soil properties and climate. Accordingly, the amount and composition of DOM in soil and that which is exported to aquatic systems are likely altered by land-use change, but these aspects have not been studied with various environmental factors and associated land-use gradients in detail. To address this, both native and cultivated soil samples from North and South America were used to extract soil-derived DOM. DOM samples were isolated and analyzed for total organic carbon concentration and solution-state nuclear magnetic resonance spectroscopy. The concentration of dissolved organic carbon (DOC) was significantly correlated with soil organic carbon concentration (r = 0.869, p < 0.01, n = 14) and relative soil organic matter degradation state (r = −0.578, p < 0.05, n = 14). Land-use change decreased the controls of environmental factors on the concentration of DOC but enhanced the correlations between DOM aromaticity and mean annual precipitation (r = −0.957, p < 0.01, n = 7) and sand concentration (r = −0.867, p < 0.05, n = 7). This study found that land-use conversion and environmental conditions alter the quantity and quality of DOM distinctly and uniquely. Here, we identified the main factors that regulate the formation of soil DOM and its potential mobility in soil profiles as well as export to aquatic ecosystems.