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Microbial carbon dynamics in nitrogen amended Arctic tundra soil: Measurement and model testing

Stapleton, L M; Crout, N M J; Säwström, Christin LU ; Marshall, W A; Poulton, P R; Tye, A M and Laybourn-Parry, J (2005) In Soil Biology & Biochemistry 37(11). p.2088-2098
Abstract
We examined the responses of grazers (protozoa and nematodes) and their main food sources to low levels of nitrogen (N) fertilisation and applied carbon (C) flux models to our data. Replicate plots of tundra soil adjacent to the Kongsfjorden (Svalbard 78°N) were amended with ammonium and nitrate at concentrations of 1 and 5 kg N ha−1 to assess the impact of anthropogenic N deposition over three summers. Bacterial abundance as determined using the fluorochrome SYBR Green and epifluorescence microscopy ranged between 9.73×108 and 102.49×108 cells/g dry wt of soil, with a significant response to N addition occurring only during the second sampling in 2001. Despite little change in bacterial biomass, bacterial production (measured by the... (More)
We examined the responses of grazers (protozoa and nematodes) and their main food sources to low levels of nitrogen (N) fertilisation and applied carbon (C) flux models to our data. Replicate plots of tundra soil adjacent to the Kongsfjorden (Svalbard 78°N) were amended with ammonium and nitrate at concentrations of 1 and 5 kg N ha−1 to assess the impact of anthropogenic N deposition over three summers. Bacterial abundance as determined using the fluorochrome SYBR Green and epifluorescence microscopy ranged between 9.73×108 and 102.49×108 cells/g dry wt of soil, with a significant response to N addition occurring only during the second sampling in 2001. Despite little change in bacterial biomass, bacterial production (measured by the incorporation of 3H thymidine into DNA) during the second sampling in 2002, increased in NH4 enriched plots compared to control and NO3 amended plots, indicating that NH4 was the preferred source of inorganic N. The main bacterial predators were heterotrophic flagellates (HNAN) and naked amoebae, which showed no significant response to the N addition. HNAN showed a correlation with bacterial abundance suggesting a dependence on bacteria as a food source. The inability of a microbial C flux model to fit our data (RWSS/data=18.6, r2=0.088) was at least partly due to insufficient bacterial production to meet the C demands of predator taxa, and high variability in the data over time. This is reflected in the performance statistics for model variants where select microbial taxa and data were removed. The optimal model in terms of predictive utility was a model with data from 2002 only, minus naked amoebae (RWSS/data=2.45, r2=0.806). (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Soil Biology & Biochemistry
volume
37
issue
11
pages
2088 - 2098
publisher
Elsevier
external identifiers
  • wos:000233501100012
  • scopus:27444433912
ISSN
0038-0717
DOI
10.1016/j.soilbio.2005.03.016
language
English
LU publication?
yes
id
2850a66b-9804-4713-8c41-d32aeb24f5cc (old id 150691)
date added to LUP
2007-06-29 07:35:12
date last changed
2017-05-21 04:16:04
@article{2850a66b-9804-4713-8c41-d32aeb24f5cc,
  abstract     = {We examined the responses of grazers (protozoa and nematodes) and their main food sources to low levels of nitrogen (N) fertilisation and applied carbon (C) flux models to our data. Replicate plots of tundra soil adjacent to the Kongsfjorden (Svalbard 78°N) were amended with ammonium and nitrate at concentrations of 1 and 5 kg N ha−1 to assess the impact of anthropogenic N deposition over three summers. Bacterial abundance as determined using the fluorochrome SYBR Green and epifluorescence microscopy ranged between 9.73×108 and 102.49×108 cells/g dry wt of soil, with a significant response to N addition occurring only during the second sampling in 2001. Despite little change in bacterial biomass, bacterial production (measured by the incorporation of 3H thymidine into DNA) during the second sampling in 2002, increased in NH4 enriched plots compared to control and NO3 amended plots, indicating that NH4 was the preferred source of inorganic N. The main bacterial predators were heterotrophic flagellates (HNAN) and naked amoebae, which showed no significant response to the N addition. HNAN showed a correlation with bacterial abundance suggesting a dependence on bacteria as a food source. The inability of a microbial C flux model to fit our data (RWSS/data=18.6, r2=0.088) was at least partly due to insufficient bacterial production to meet the C demands of predator taxa, and high variability in the data over time. This is reflected in the performance statistics for model variants where select microbial taxa and data were removed. The optimal model in terms of predictive utility was a model with data from 2002 only, minus naked amoebae (RWSS/data=2.45, r2=0.806).},
  author       = {Stapleton, L M and Crout, N M J and Säwström, Christin and Marshall, W A and Poulton, P R and Tye, A M and Laybourn-Parry, J},
  issn         = {0038-0717},
  language     = {eng},
  number       = {11},
  pages        = {2088--2098},
  publisher    = {Elsevier},
  series       = {Soil Biology & Biochemistry},
  title        = {Microbial carbon dynamics in nitrogen amended Arctic tundra soil: Measurement and model testing},
  url          = {http://dx.doi.org/10.1016/j.soilbio.2005.03.016},
  volume       = {37},
  year         = {2005},
}