• Media type: E-Article
  • Title: Adding dissolved organic carbon to simulate freeze‐thaw related N2O emissions from soil
  • Contributor: Sehy, Ulrike; Dyckmans, Jens; Ruser, Reiner; Munch, Jean Charles
  • Published: Wiley, 2004
  • Published in: Journal of Plant Nutrition and Soil Science
  • Extent: 471-478
  • Language: English
  • DOI: 10.1002/jpln.200421393
  • ISSN: 1436-8730; 1522-2624
  • Keywords: Plant Science ; Soil Science
  • Abstract: <jats:title>Abstract</jats:title><jats:p>It has been assumed that high winter N<jats:sub>2</jats:sub>O emissions from soils are the result of increased amounts of microbially available organic C liberated during freezing and metabolized during subsequent thawing. In a laboratory experiment, we attempted to simulate freeze‐thaw events by adding dissolved organic C (DOC) to sieved soil of high water content (95% water‐filled pore space). In a full factorial design, CO<jats:sub>2</jats:sub> and N<jats:sub>2</jats:sub>O emissions of a) soil samples provided with DOC extracted from frozen soil and b) soil samples frozen for 46 days and thawed were compared. Additionally, NO<jats:styled-content>$_3^-$<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/tex2gif-ueqn-1.gif" xlink:title="equation image" /></jats:styled-content>, DOC and microbial ATP contents of all treatments were repeatedly analyzed during the experiment.</jats:p><jats:p>The addition of DOC to unfrozen soil (–F+C) resulted in a substantial (22‐fold) increase in N<jats:sub>2</jats:sub>O emissions as compared to the control (–F–C). However, following thawing, the increase in N<jats:sub>2</jats:sub>O emissions was much larger (828‐fold in +F–C and 1243‐fold in +F+C). Freezing, but not the addition of DOC led to increased CO<jats:sub>2</jats:sub> emissions. Neither treatment affected microbial adenylate content. By adding <jats:sup>15</jats:sup>N‐labeled nitrate to the soil samples, the main process leading to elevated N<jats:sub>2</jats:sub>O flux rates after both DOC addition and freeze‐thaw treatment was identified as denitrification.</jats:p><jats:p>We conclude that the availability of C substrate plays an important role for freeze‐thaw‐related N<jats:sub>2</jats:sub>O emissions. However, the fact that the simulated treatment and the freeze‐thaw treatment yielded significantly different amounts of N<jats:sub>2</jats:sub>O suggests that both quantity and quality of available C differed between the treatments. The localization of the liberated substrate, <jats:italic>i.e.</jats:italic>, the availability <jats:italic>in situ</jats:italic>, seems to be of major importance for the amount of N<jats:sub>2</jats:sub>O produced.</jats:p>
  • Description: <jats:title>Abstract</jats:title><jats:p>It has been assumed that high winter N<jats:sub>2</jats:sub>O emissions from soils are the result of increased amounts of microbially available organic C liberated during freezing and metabolized during subsequent thawing. In a laboratory experiment, we attempted to simulate freeze‐thaw events by adding dissolved organic C (DOC) to sieved soil of high water content (95% water‐filled pore space). In a full factorial design, CO<jats:sub>2</jats:sub> and N<jats:sub>2</jats:sub>O emissions of a) soil samples provided with DOC extracted from frozen soil and b) soil samples frozen for 46 days and thawed were compared. Additionally, NO<jats:styled-content>$_3^-$<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/tex2gif-ueqn-1.gif" xlink:title="equation image" /></jats:styled-content>, DOC and microbial ATP contents of all treatments were repeatedly analyzed during the experiment.</jats:p><jats:p>The addition of DOC to unfrozen soil (–F+C) resulted in a substantial (22‐fold) increase in N<jats:sub>2</jats:sub>O emissions as compared to the control (–F–C). However, following thawing, the increase in N<jats:sub>2</jats:sub>O emissions was much larger (828‐fold in +F–C and 1243‐fold in +F+C). Freezing, but not the addition of DOC led to increased CO<jats:sub>2</jats:sub> emissions. Neither treatment affected microbial adenylate content. By adding <jats:sup>15</jats:sup>N‐labeled nitrate to the soil samples, the main process leading to elevated N<jats:sub>2</jats:sub>O flux rates after both DOC addition and freeze‐thaw treatment was identified as denitrification.</jats:p><jats:p>We conclude that the availability of C substrate plays an important role for freeze‐thaw‐related N<jats:sub>2</jats:sub>O emissions. However, the fact that the simulated treatment and the freeze‐thaw treatment yielded significantly different amounts of N<jats:sub>2</jats:sub>O suggests that both quantity and quality of available C differed between the treatments. The localization of the liberated substrate, <jats:italic>i.e.</jats:italic>, the availability <jats:italic>in situ</jats:italic>, seems to be of major importance for the amount of N<jats:sub>2</jats:sub>O produced.</jats:p>
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