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Site-dependent N uptake from N-form mixtures by arctic plants, soil microbes and ectomycorrhizal fungi

Engelbrecht Clemmensen, Karina; Lærkedal Sørensen, Pernille; Michelsen, Anders; Jonasson, Sven and Ström, Lena LU (2008) In Oecologia 155(4). p.771-783
Abstract (Swedish)
Abstract in Undetermined

Soil microbes constitute an important control on nitrogen (N) turnover and retention in arctic ecosystems where N availability is the main constraint on primary production. Ectomycorrhizal (ECM) symbioses may facilitate plant competition for the specific N pools available in various arctic ecosystems. We report here our study on the N uptake patterns of coexisting plants and microbes at two tundra sites with contrasting dominance of the circumpolar ECM shrub Betula nana. We added equimolar mixtures of glycine-N, NH4+-N and NO3--N, with one N form labelled with N-15 at a time, and in the case of glycine, also labelled with C-13, either directly to the soil or to ECM fungal ingrowth bags. After 2... (More)
Abstract in Undetermined

Soil microbes constitute an important control on nitrogen (N) turnover and retention in arctic ecosystems where N availability is the main constraint on primary production. Ectomycorrhizal (ECM) symbioses may facilitate plant competition for the specific N pools available in various arctic ecosystems. We report here our study on the N uptake patterns of coexisting plants and microbes at two tundra sites with contrasting dominance of the circumpolar ECM shrub Betula nana. We added equimolar mixtures of glycine-N, NH4+-N and NO3--N, with one N form labelled with N-15 at a time, and in the case of glycine, also labelled with C-13, either directly to the soil or to ECM fungal ingrowth bags. After 2 days, the vegetation contained 5.6, 7.7 and 9.1% (heath tundra) and 7.1, 14.3 and 12.5% (shrub tundra) of the glycine-, NH4+- and NO3--N-15, respectively, recovered in the plant-soil system, and the major part of N-15 in the soil was immobilized by microbes (chloroform fumigation-extraction). In the subsequent 24 days, microbial N turnover transferred about half of the immobilized N-15 to the non-extractable soil organic N pool, demonstrating that soil microbes played a major role in N turnover and retention in both tundra types. The ECM mycelial communities at the two tundras differed in N-form preferences, with a higher contribution of glycine to total N uptake at the heath tundra; however, the ECM mycelial communities at both sites strongly discriminated against NO3-. Betula nana did not directly reflect ECM mycelial N uptake, and we conclude that N uptake by ECM plants is modulated by the N uptake patterns of both fungal and plant components of the symbiosis and by competitive interactions in the soil. Our field study furthermore showed that intact free amino acids are potentially important N sources for arctic ECM fungi and plants as well as for soil microorganisms. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Oecologia
volume
155
issue
4
pages
771 - 783
publisher
Springer
external identifiers
  • wos:000254238700011
  • scopus:41149086128
ISSN
1432-1939
DOI
10.1007/s00442-008-0962-9
language
English
LU publication?
yes
id
e8dfa2a4-1c94-442c-aa8c-b936c9e05786 (old id 715486)
date added to LUP
2007-12-14 11:28:43
date last changed
2017-11-19 03:54:42
@article{e8dfa2a4-1c94-442c-aa8c-b936c9e05786,
  abstract     = {<b>Abstract in Undetermined</b><br/><br>
Soil microbes constitute an important control on nitrogen (N) turnover and retention in arctic ecosystems where N availability is the main constraint on primary production. Ectomycorrhizal (ECM) symbioses may facilitate plant competition for the specific N pools available in various arctic ecosystems. We report here our study on the N uptake patterns of coexisting plants and microbes at two tundra sites with contrasting dominance of the circumpolar ECM shrub Betula nana. We added equimolar mixtures of glycine-N, NH4+-N and NO3--N, with one N form labelled with N-15 at a time, and in the case of glycine, also labelled with C-13, either directly to the soil or to ECM fungal ingrowth bags. After 2 days, the vegetation contained 5.6, 7.7 and 9.1% (heath tundra) and 7.1, 14.3 and 12.5% (shrub tundra) of the glycine-, NH4+- and NO3--N-15, respectively, recovered in the plant-soil system, and the major part of N-15 in the soil was immobilized by microbes (chloroform fumigation-extraction). In the subsequent 24 days, microbial N turnover transferred about half of the immobilized N-15 to the non-extractable soil organic N pool, demonstrating that soil microbes played a major role in N turnover and retention in both tundra types. The ECM mycelial communities at the two tundras differed in N-form preferences, with a higher contribution of glycine to total N uptake at the heath tundra; however, the ECM mycelial communities at both sites strongly discriminated against NO3-. Betula nana did not directly reflect ECM mycelial N uptake, and we conclude that N uptake by ECM plants is modulated by the N uptake patterns of both fungal and plant components of the symbiosis and by competitive interactions in the soil. Our field study furthermore showed that intact free amino acids are potentially important N sources for arctic ECM fungi and plants as well as for soil microorganisms.},
  author       = {Engelbrecht Clemmensen, Karina and Lærkedal Sørensen, Pernille and Michelsen, Anders and Jonasson, Sven and Ström, Lena},
  issn         = {1432-1939},
  language     = {eng},
  number       = {4},
  pages        = {771--783},
  publisher    = {Springer},
  series       = {Oecologia},
  title        = {Site-dependent N uptake from N-form mixtures by arctic plants, soil microbes and ectomycorrhizal fungi},
  url          = {http://dx.doi.org/10.1007/s00442-008-0962-9},
  volume       = {155},
  year         = {2008},
}