From the litter layer to the saprolite: Chemical changes in water-soluble soil organic matter and their correlation to microbial community composition |
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Affiliation: | 1. Department of Environmental Studies, University of Colorado, Boulder, CO 80309, USA;2. Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA;3. Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO 80309, USA;4. Department of Geography, University of Colorado, Boulder, CO 80309, USA;5. Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80303, USA;6. Cooperative Institute for Research in the Environmental Science, University of Colorado, Boulder, CO 80309, USA;1. Environmental Engineering Research Centre, School of Planning, Architecture, and Civil Engineering, Queen’s University of Belfast, Belfast BT9 5AG, Northern Ireland;2. Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, 37831 TN, USA;1. Delaware Environmental Institute, University of Delaware, Newark, DE 19716-7310, USA;2. Department of Earth & Environmental Science, University of Pennsylvania, Philadelphia, PA 19104-6316, USA;3. Department of Crop & Soil Science, University of Georgia, Athens, GA 30602-0000, USA;1. University of São Paulo, College of Agriculture “Luiz de Queiroz”, Soil Science and Plant Nutrition Dept., Av. Pádua Dias, 11, ZIP 13418900, Piracicaba, SP, Brazil;2. Federal Rural University of Pernambuco (UFRPE), Agronomy Department, Rua Dom Manoel de Medeiros, s/n. Campus Dois Irmãos., ZIP 52171-900, Recife, PE, Brazil;1. Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA, USA;2. School of Marine Science and Policy, College of Earth, Ocean, and Environment, University of Delaware, Lewes, DE, USA;3. Department of Geological Sciences, University of Florida, Gainesville, FL, USA;4. Department of Geological Sciences, East Carolina University, Greenville, NC, USA;1. Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China;2. State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China;3. College of Resource and Environment, Yunnan University, Kunming, 650091, China;4. Shenzhen Academy of Environmental Sciences, Shenzhen, 518001, China;5. Department of Biostatistics and Epidemiology School of Public Health and Health Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA |
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Abstract: | Organic matter content and chemistry is vital to the structure and function of soil systems, but while organic matter is recognized as biogeochemically important, its chemical interaction with soil processes is not well understood. In this study we used fluorescence spectroscopy, which has been used extensively for understanding the role of organic matter in aquatic systems, to identify chemical changes in organic matter with depth in a soil system. Soil was collected from nine different pits in a first-order montane catchment in the Colorado Front Range. The water-soluble soil organic matter was extracted from each sample and fluorescence and UV–vis spectroscopy was used to analyze its chemical character. While organic matter chemistry had little correlation with landscape location and local vegetation, there were noticeable consistent trends between soil horizon and organic matter chemistry in each pit. Total organic matter decreased with depth and became less aromatic with increasing depth. This less aromatic material in the saprolite also had a greater microbial signature. The redox character of the organic matter accompanied this change in source and molecular structure, with more oxidized character corresponding with organic matter with more microbial input and more reduced character corresponding to organic matter with more plant input. A concurrent investigation of the microbial population of the same soil samples also showed microbial population composition varying more with soil depth than landscape position, and depth changes in microbial diversity occurred concomitantly with depth changes in organic matter chemistry. |
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Keywords: | Water soluble organic matter (WSOM) Soil depth UV–vis absorbance and fluorescence spectroscopy XAD-8 resin fractionation Organic matter/microbe interactions EEM-PARAFAC |
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