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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
; ; and
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
2016-04-01 12:10:36
date last changed
2024-05-08 05:49:43
@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}},
  doi          = {{10.1111/j.1600-0706.2009.17796.x}},
  volume       = {{118}},
  year         = {{2009}},
}