Land-Use Change and Environmental Properties Alter the Quantity and Molecular Composition of Soil-Derived Dissolved Organic Matter

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.

Changes in water‐extractable organic matter in tropical forest and agricultural soils as detected by the DRIFT spectroscopy technique

“…The dissolved organic components are involved in important biochemical processes since the partition between solid and liquid phases affect the SOM accumulation (Kindler et al, 2011; Paul, 2016), influence the microbial biomass (Dong et al, 2021), mediate the soil–plant interactions and the crop development (Olaetxea et al, 2018; Verrillo et al, 2021), and may interact with the environmental behavior of organic and inorganic pollutants (Borggaard et al, 2019; Sun et al, 2021). Besides the large reactivity, the relatively low abundance, as compared with the total soil organic matter (SOM), makes the DOM sensitive to land use and management practices (Chantigny, 2003), thus acting as both a major pool of actively cycling organic carbon in soils and useful indicator to assess large‐scale changes in soil quality (Jones et al, 2014; Tong et al, 2021). The dynamic of DOM acquires a particular role in tropical environments where the fast OC turnover and the humid climate improve the release of dissolved organic fraction and speed up the exchange processes between soil and water with a large influence on biological and physical–chemical features of forestry and agro‐ecosystems (Tadini, Constantino, et al, 2015; Tadini, Pantano, et al, 2015).…”

Human Activity Coupled With Climate Change Strengthens the Role of Lakes as an Active Pipe of Dissolved Organic Matter

“…The effect of climate is also associated with multiple indirect pathways: (a) indirectly altering allochthonous DOM inputs via shaping land cover (Creed et al., 2018; Jane et al., 2017; Williamson et al., 2014; Zhang et al., 2010), (b) modifying autochthonous DOM generation through impacting nutrient input (e.g., precipitation increases total phosphorus and total nitrogen fluxes) (Garcia et al., 2015), and (c) mediating lake hydrology via the change of precipitation (e.g., the retention time decreases due to high precipitation) (Queimaliños et al., 2019). Land cover performs via (a) a direct pathway, that is, altering allochthonous DOM inputs by mediating soil OM production, storage, and composition (Larson et al., 2014; Sepp et al., 2019; Tong et al., 2021; Yates et al., 2019), and (b) an indirect pathway, that is, impacting autochthonous DOM generation through changing nutrient inputs (e.g., the degradation of pasture into bareland leads to a decrease in soil total phosphorus and total nitrogen) (Liu et al., 2018). Societal development alters DOM composition mainly by exporting anthropogenic organic substances (Lu et al., 2014; Williams et al., 2016) and stimulating autochthonous productivity (Lu et al., 2013; Wagner et al., 2015; Xenopoulos et al., 2021).…”

“…The effects of climate can operate directly, that is, through influencing in‐lake generation and processing of DOM (Du, Chen, et al., 2021), or indirectly, for example, through altering land cover and thus allochthonous inputs (Creed et al., 2018; Jane et al., 2017; Williamson et al., 2014; Zhang et al., 2010). Land cover can influence allochthonous DOM in lakes directly via mediating soil OM production, storage, and decomposition (Larson et al., 2014; Sepp et al., 2019; Tong et al., 2021; Yates et al., 2019), as well as indirectly via altering autochthonous DOM production and decomposition through changing nutrient inputs (Bergstrom & Karlsson, 2019). Human activities can also operate directly through altering the source, composition, and reactivity of DOM in various water bodies by changing soil OM characters and flow paths and exporting anthropogenic organic substances (Chen et al., 2021; Lu et al., 2013; Sankar et al., 2020; Williams et al., 2016), and operate indirectly through stimulating autochthonous productivity (Lu et al., 2013; Wagner et al., 2015; Xenopoulos et al., 2021).…”

Influence of land use and different plant residues on isotopic carbon distribution of total and water extractable organic matter in an incubation experiment with weathered tropical soil

“…Since the DOM usually represents a minor fraction of the overall SOC pool (Chantigny et al, 2014; da Silva et al, 2021). , it is readily affected by land use and soil management and is hence considered a valuable probe to follow the OC cycling in both forests and cropped soils (Paul, 2016; Tong et al, 2021).…”

“…Furthermore, the dissolved bioactive organic compounds mediate both the soil-plant interactions within the rhizosphere (Baía et al, 2020) and the soilliquid phase equilibrium related to accumulation processes of soil organic carbon (SOC) (Riley et al, 2014). Since the DOM usually represents a minor fraction of the overall SOC pool (Chantigny et al, 2014;da Silva et al, 2021)., it is readily affected by land use and soil management and is hence considered a valuable probe to follow the OC cycling in both forests and cropped soils (Paul, 2016;Tong et al, 2021).…”