Abstract
Water-extractable organic matter (WEOM) in soil is the critical substrate that fuels microbial-driven biogeochemical cycles. However, questions remain regarding whether and how expanding impervious surface area under global urbanization may alter soil WEOM cycling. Based on absorbance and fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), we compared the content and chemical signatures of soil WEOM under impervious surfaces with those in adjoining open areas and evaluated the impacts of types (complete sealing by concrete and partial sealing by house structures) and durations (1.5, 27, and 114 years) of impervious surface coverage. The content of soil WEOM and its chromophoric and fluorescent fractions were not significantly changed (less than 20%) after 1.5 years of coverage by concrete and house structures. However, these parameters decreased by more than 30% with 27 and 114 years of coverage by the residential home structures. The microbial-humic-like and protein-like fluorescent WEOM persisted preferentially over the terrestrial-humic-like and nonfluorescent WEOM. FT-ICR MS results suggest various degrees of depletion of biochemical groups in WEOM. While the water-extractable lipid-like compounds increased with 1.5 years of coverage, all studied biochemical groups were depleted with long-term coverage, which might reduce the microbial processing of suberin-derived compounds. This study highlights the remarkable impacts of soil sealing on reducing substrate availability for microbial carbon processing in urban environments.
Highlights
Soil organic matter (SOM) is a critical regulator of the global carbon cycle, and its water-extractable fraction is referred to as soil-derived dissolved organic matter (DOM) or water-extractable organic matter (WEOM), which represents the most mobile and active carbon pool of SOM (Kalbitz et al, 2000; Bolan et al, 2011)
With 1.5 years of coverage by impervious surfaces, WEOC/soil organic carbon (SOC) did not change significantly compared to Surf-ref or subsurface reference (Sub-ref)
The results showed that chromophoric dissolved organic matter (CDOM) was more abundant in Surf-ref than in Sub-ref (Figure 1C), which may have been caused by the higher WEOC concentration and more phenol components from plant and litter leachates in the surface soil than in subsurface soil (Stubbins et al, 2017; Ye et al, 2020)
Summary
Soil organic matter (SOM) is a critical regulator of the global carbon cycle, and its water-extractable fraction is referred to as soil-derived dissolved organic matter (DOM) or water-extractable organic matter (WEOM), which represents the most mobile and active carbon pool of SOM (Kalbitz et al, 2000; Bolan et al, 2011). WEOM is the main source of carbon and energy for soil microorganisms and regulates the carbon cycle and associated nutrient cycles (Wu et al, 2018) and an important. The chemodiversity of WEOM has been related to soil physical-chemical properties and soil microbial community characteristics (Roth et al, 2019; Ding et al, 2020). Anthropogenic irruptions, such as global warming, increased nitrogen deposition, and frequently occurring fires, could alter the composition of WEOM (Dittmar et al, 2012; Fröberg et al, 2013; Wang et al, 2019)
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