Linking Carbon Saturation Concepts to Nitrogen Saturation and Retention

Michael J. Castellano, Jason P. Kaye, Henry Lin, John P. Schmidt

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Recent advances in soil C saturation concepts have increased our understanding of soil C storage and mineralization without explicit links to N retention and saturation theories. Here, we exploit soil texture and organic matter (OM) gradients in a Maryland, USA hardwood forest to test hypotheses that link soil organic C saturation with soil 15N retention and nitrification. At our site, mineral-associated OM (MAOM) N concentrations in the silt + clay particle fraction (g MAOM-N g silt + clay -1) were negatively correlated with the fraction of NH 4-N transferred to MAOM during a 3-day in situ incubation (R = -0. 85), but positively correlated with potential net nitrification (R = 0. 76). Moreover, the fraction of NH 4-N transferred to MAOM was negatively correlated with potential net nitrification (R = -0. 76). Due to physico-chemical stabilization mechanisms, MAOM is considered to be resistant to mineralization. Carbon saturation theory suggests that the proportion of new C inputs that can be stabilized in MAOM decreases in proportion to the amount of C already present in the fraction; C inputs not stabilized in MAOM are susceptible to rapid mineralization. We demonstrate that NH 4-N stabilization in MAOM is similar to C stabilization in MAOM and associated with nitrification, thereby extending soil C saturation theory to mineral N and linking it with N retention and saturation theories. These data and concepts complement N saturation models that emphasize vegetation type, N input levels, and microbial turnover. Incorporating the OM retention capacity of fine mineral particles into N saturation theory can improve predictions of N saturation rates and resolve inconsistent relationships between soil organic matter, texture, N mineralization, and N retention.

Original languageEnglish (US)
Pages (from-to)175-187
Number of pages13
JournalEcosystems
Volume15
Issue number2
DOIs
StatePublished - Mar 1 2012

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Environmental Chemistry
  • Ecology

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