Turnover of labile and recalcitrant soil carbon differ in response to nitrate and ammonium deposition in an ombrotrophic peatland

Pauline M. Currey, David Johnson, Lucy J. Sheppard, Ian D. Leith, Hannah Toberman, Rene van der Wal, Lorna A. Dawson, Rebekka R. E. Artz

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Abstract

The effects of 4 years of simulated nitrogen deposition, as nitrate (NO3-) and ammonium (NH4+), on microbial carbon turnover were studied in an ombrotrophic peatland. We investigated the mineralization of simple forms of carbon using MicroResp (TM) measurements (a multiple substrate induced respiration technique) and the activities of four soil enzymes involved in the decomposition of more complex forms of carbon or in nutrient acquisition: N-acetyl-glucosaminidase (NAG), cellobiohydrolase (CBH), acid phosphatase (AP), and phenol oxidase (PO). The potential mineralization of labile forms of carbon was significantly enhanced at the higher N additions, especially with NH4+ amendments, while potential enzyme activities involved in breakdown of more complex forms of carbon or nutrient acquisition decreased slightly (NAG and CBH) or remained unchanged (AP and PO) with N amendments. This study also showed the importance of distinguishing between NO3- and NH4+ amendments, as their impact often differed. It is possible that the limited response on potential extracellular enzyme activity is due to other factors, such as limited exposure to the added N in the deeper soil or continued suboptimal functioning of the enzymes due to the low pH, possibly via the inhibitory effect of low phenol oxidase activity.

Original languageEnglish
Pages (from-to)2307-2321
Number of pages15
JournalGlobal Change Biology
Volume16
Issue number8
DOIs
Publication statusPublished - Aug 2010

Keywords

  • carbon turnover
  • enzyme activity
  • nitrogen deposition
  • peatland
  • substrate-induced respiration
  • phenol oxidase activity
  • microbial community
  • extracellular enzyme-activity
  • term nitrogen deposition
  • litter decomposition
  • summer drought
  • whole soil
  • vegetation
  • phosphorus
  • sphagnum

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