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Plant-microbial competition for nitrogen uncoupled from soil C:N ratios

Månsson, Katarina LU ; Bengtson, Per LU ; Falkengren-Grerup, Ursula LU and Bengtsson, Göran LU (2009) In Oikos 118(12). p.1908-1916
Abstract
A green house experiment was designed to test the idea that competition for inorganic nitrogen (N) between plants and heterotrophic microorganisms occurs in soils with high C:N ratios, qualifying for N limited microbial activity, but not at low C:N ratios. The short- term (24 h) N-15 uptake by the grass Festuca gigantea and microorganisms in planted and unplanted soils was determined, and the bacterial activity was measured by the H-3-thymidine incorporation technique. Two deciduous forest soils, with C:N-ratios of 20 and 31, and the 20 soil amended with litter to a C:N ratio of 34, were used. A novel and important part of the experimental design was the preparation of the unplanted reference soil with plants present until the competition... (More)
A green house experiment was designed to test the idea that competition for inorganic nitrogen (N) between plants and heterotrophic microorganisms occurs in soils with high C:N ratios, qualifying for N limited microbial activity, but not at low C:N ratios. The short- term (24 h) N-15 uptake by the grass Festuca gigantea and microorganisms in planted and unplanted soils was determined, and the bacterial activity was measured by the H-3-thymidine incorporation technique. Two deciduous forest soils, with C:N-ratios of 20 and 31, and the 20 soil amended with litter to a C:N ratio of 34, were used. A novel and important part of the experimental design was the preparation of the unplanted reference soil with plants present until the competition assay started by the addition of N-15 labelled ammonium (NH4+) or nitrate (NO3-). The results suggested that plants and soil microorganisms competed for mineral N but under influence of other factors than the soil C:N ratio. The plants reduced the microbial uptake of NH4+ and NO3- in the soil with low C:N ratio, which also had the lowest bacterial activity. The plants had a larger N uptake than microorganisms in the two natural soils but smaller in the litter-amended, and their presence enhanced the bacterial activity, especially in the latter soil. The litter-amended soil with its high C:N ratio and easily decomposable C was the soil that best fulfilled the criteria for competition, including a net consumption of mineral N during the assay, the lowest plant uptake of mineral N due to the high N immobilization by microorganisms, and a reduced microbial N-15 uptake-to-bacterial activity in the presence of plants. Thus, other factors, such as the decomposability of the soil C and the bacterial activity, were more important than the soil C:N ratio to the outcome of plant-microbial competition for N. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Oikos
volume
118
issue
12
pages
1908 - 1916
publisher
Wiley-Blackwell
external identifiers
  • wos:000272306900016
  • scopus:71049132172
ISSN
1600-0706
DOI
10.1111/j.1600-0706.2009.17796.x
language
English
LU publication?
yes
id
596b537d-65e8-4ae1-8390-ed4cfd9ec309 (old id 1533402)
date added to LUP
2010-01-28 11:04:03
date last changed
2017-04-16 03:34:55
@article{596b537d-65e8-4ae1-8390-ed4cfd9ec309,
  abstract     = {A green house experiment was designed to test the idea that competition for inorganic nitrogen (N) between plants and heterotrophic microorganisms occurs in soils with high C:N ratios, qualifying for N limited microbial activity, but not at low C:N ratios. The short- term (24 h) N-15 uptake by the grass Festuca gigantea and microorganisms in planted and unplanted soils was determined, and the bacterial activity was measured by the H-3-thymidine incorporation technique. Two deciduous forest soils, with C:N-ratios of 20 and 31, and the 20 soil amended with litter to a C:N ratio of 34, were used. A novel and important part of the experimental design was the preparation of the unplanted reference soil with plants present until the competition assay started by the addition of N-15 labelled ammonium (NH4+) or nitrate (NO3-). The results suggested that plants and soil microorganisms competed for mineral N but under influence of other factors than the soil C:N ratio. The plants reduced the microbial uptake of NH4+ and NO3- in the soil with low C:N ratio, which also had the lowest bacterial activity. The plants had a larger N uptake than microorganisms in the two natural soils but smaller in the litter-amended, and their presence enhanced the bacterial activity, especially in the latter soil. The litter-amended soil with its high C:N ratio and easily decomposable C was the soil that best fulfilled the criteria for competition, including a net consumption of mineral N during the assay, the lowest plant uptake of mineral N due to the high N immobilization by microorganisms, and a reduced microbial N-15 uptake-to-bacterial activity in the presence of plants. Thus, other factors, such as the decomposability of the soil C and the bacterial activity, were more important than the soil C:N ratio to the outcome of plant-microbial competition for N.},
  author       = {Månsson, Katarina and Bengtson, Per and Falkengren-Grerup, Ursula and Bengtsson, Göran},
  issn         = {1600-0706},
  language     = {eng},
  number       = {12},
  pages        = {1908--1916},
  publisher    = {Wiley-Blackwell},
  series       = {Oikos},
  title        = {Plant-microbial competition for nitrogen uncoupled from soil C:N ratios},
  url          = {http://dx.doi.org/10.1111/j.1600-0706.2009.17796.x},
  volume       = {118},
  year         = {2009},
}