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Uptake of and Preference for Nitrate, Ammonium and Amino Acids by Understory Species in Deciduous Forests

Zätterström, Magnus LU (2002)
Abstract
AbstractThe uptake of different nitrogen forms by understory species was studied in field and laboratory. Species of the understory in deciduous forests have previously been thought to take up and assimilate only inorganic nitrogen sources. However, species also have the opportunity to assimilate amino acids, usually in low rates compared with ammonium, according to solution culture studies, but may have relatively high uptake rates in soil, as indicated by measurements of uptake rates with 15N-labelled compounds, at least of the amino acid glycine. The uptake of amino acids increased after a drying-rewetting cycle, whereas uptake of ammonium radically decreased, indicating a shift from inorganic nitrogen to organic nitrogen uptake after... (More)
AbstractThe uptake of different nitrogen forms by understory species was studied in field and laboratory. Species of the understory in deciduous forests have previously been thought to take up and assimilate only inorganic nitrogen sources. However, species also have the opportunity to assimilate amino acids, usually in low rates compared with ammonium, according to solution culture studies, but may have relatively high uptake rates in soil, as indicated by measurements of uptake rates with 15N-labelled compounds, at least of the amino acid glycine. The uptake of amino acids increased after a drying-rewetting cycle, whereas uptake of ammonium radically decreased, indicating a shift from inorganic nitrogen to organic nitrogen uptake after plants were exposed to stress.



The hypothesis that less acid-tolerant species of the understory take up nitrate to a higher degree than acid-tolerant species was investigated in the field by measurements of the potential nitrification activity in the rhizosphere and bulk soil, and an investigation of the natural abundance of 15N in the aboveground biomass. Concerning nitrification, less acid-tolerant species usually exhibited higher nitrification rates in their rhizosphere than in the bulk soil, and also showed higher nitrification in their rhizosphere than other species at the same site. Differences in nitrification rates were interpreted as a relatively higher uptake of nitrate. The less acid-tolerant species also showed lower values of natural abundance of 15N, which was interpreted as a relatively higher uptake of nitrate as nitrate should have lower values than ammonium, but differences could be due to other reasons.



The understory seldom makes any large contributions to the biomass of the ecosystem, but the turnover of nutrients is faster than for the trees. Concerning uptake of nitrate (measured as the activity of the enzyme nitrate reductase), the understory in oak forests makes a considerable contribution during spring, but could also be of importance during summer as the same uptake of nitrate per unit area was observed by the tree and the understory layer at some sites. The importance of the understory is of special interest as the risk of nitrate leaching is highest during spring, when trees are inactive. (Less)
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author
opponent
  • Näsholm, Torgny, Institutionen for Skoglig Genetik och Växtfysiologi, SLU Umeå
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Soil Science, agricultural hydrology, Lantbrukshydrologi, marklära, Fixation of nitrogen, Kvävefixering, Växtekologi, Plant ecology, wild plants., understory, rhizosphere, preference, oak forests, NRA, nitrification, nitrate, delta15N, 15N, glutamate, glycine, drying-rewetting, amino acids, ammonium
pages
102 pages
publisher
Plant Ecology, Ecology Building, SE-223 62 Lund
defense location
Blå Hallen, Ecology Building, Sölveg 37 Lund
defense date
2002-02-08 10:15
external identifiers
  • other:ISRN: SE-LUNBDS/NBBE-02/1065+102
ISBN
91-7105-168-6
language
English
LU publication?
yes
id
800b0cdb-3303-45f4-8269-05fee138c4df (old id 464276)
date added to LUP
2007-09-06 11:07:44
date last changed
2016-09-19 08:45:02
@phdthesis{800b0cdb-3303-45f4-8269-05fee138c4df,
  abstract     = {AbstractThe uptake of different nitrogen forms by understory species was studied in field and laboratory. Species of the understory in deciduous forests have previously been thought to take up and assimilate only inorganic nitrogen sources. However, species also have the opportunity to assimilate amino acids, usually in low rates compared with ammonium, according to solution culture studies, but may have relatively high uptake rates in soil, as indicated by measurements of uptake rates with 15N-labelled compounds, at least of the amino acid glycine. The uptake of amino acids increased after a drying-rewetting cycle, whereas uptake of ammonium radically decreased, indicating a shift from inorganic nitrogen to organic nitrogen uptake after plants were exposed to stress.<br/><br>
<br/><br>
The hypothesis that less acid-tolerant species of the understory take up nitrate to a higher degree than acid-tolerant species was investigated in the field by measurements of the potential nitrification activity in the rhizosphere and bulk soil, and an investigation of the natural abundance of 15N in the aboveground biomass. Concerning nitrification, less acid-tolerant species usually exhibited higher nitrification rates in their rhizosphere than in the bulk soil, and also showed higher nitrification in their rhizosphere than other species at the same site. Differences in nitrification rates were interpreted as a relatively higher uptake of nitrate. The less acid-tolerant species also showed lower values of natural abundance of 15N, which was interpreted as a relatively higher uptake of nitrate as nitrate should have lower values than ammonium, but differences could be due to other reasons.<br/><br>
<br/><br>
The understory seldom makes any large contributions to the biomass of the ecosystem, but the turnover of nutrients is faster than for the trees. Concerning uptake of nitrate (measured as the activity of the enzyme nitrate reductase), the understory in oak forests makes a considerable contribution during spring, but could also be of importance during summer as the same uptake of nitrate per unit area was observed by the tree and the understory layer at some sites. The importance of the understory is of special interest as the risk of nitrate leaching is highest during spring, when trees are inactive.},
  author       = {Zätterström, Magnus},
  isbn         = {91-7105-168-6},
  keyword      = {Soil Science,agricultural hydrology,Lantbrukshydrologi,marklära,Fixation of nitrogen,Kvävefixering,Växtekologi,Plant ecology,wild plants.,understory,rhizosphere,preference,oak forests,NRA,nitrification,nitrate,delta15N,15N,glutamate,glycine,drying-rewetting,amino acids,ammonium},
  language     = {eng},
  pages        = {102},
  publisher    = {Plant Ecology, Ecology Building, SE-223 62 Lund},
  school       = {Lund University},
  title        = {Uptake of and Preference for Nitrate, Ammonium and Amino Acids by Understory Species in Deciduous Forests},
  year         = {2002},
}