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Nitrogen Isotope Patterns in Alaskan Black Spruce Reflect Organic Nitrogen Sources and the Activity of Ectomycorrhizal Fungi

Mayor, Jordan R.; Schuur, Edward A. G.; Mack, Michelle C.; Hollingsworth, Terresa N. and Bååth, Erland LU (2012) In Ecosystems 15(5). p.819-831
Abstract
Global patterns in soil, plant, and fungal stable isotopes of N (delta N-15) show promise as integrated metrics of N cycling, particularly the activity of ectomycorrhizal (ECM) fungi. At small spatial scales, however, it remains difficult to differentiate the underlying causes of plant delta N-15 variability and this limits the application of such measurements to better understand N cycling. We conducted a landscape-scale analysis of delta N-15 values from 31 putatively N-limited monospecific black spruce (Picea mariana) stands in central Alaska to assess the two main hypothesized sources of plant delta N-15 variation: differing sources and ECM fractionation. We found roughly 20% of the variability in black spruce foliar N and delta N-15... (More)
Global patterns in soil, plant, and fungal stable isotopes of N (delta N-15) show promise as integrated metrics of N cycling, particularly the activity of ectomycorrhizal (ECM) fungi. At small spatial scales, however, it remains difficult to differentiate the underlying causes of plant delta N-15 variability and this limits the application of such measurements to better understand N cycling. We conducted a landscape-scale analysis of delta N-15 values from 31 putatively N-limited monospecific black spruce (Picea mariana) stands in central Alaska to assess the two main hypothesized sources of plant delta N-15 variation: differing sources and ECM fractionation. We found roughly 20% of the variability in black spruce foliar N and delta N-15 values to be correlated with the concentration and delta N-15 values of soil NH4 (+) and dissolved organic N (DON) pools, respectively. However, N-15-based mixing models from 24 of the stands suggested that fractionation by ECM fungi obscures the N-15 signature of soil N pools. Models, regressions, and N abundance data all suggested that increasing dependence on soil DON to meet black spruce growth demands predicates increasing reliance on ECM-derived N and that black spruce, on average, received 53% of its N from ECM fungi. Future research should partition the delta N-15 values within the soil DON pool to determine how choice of soil delta N-15 values influence modeled ECM activity. The C balance of boreal forests is tightly linked to N cycling and delta N-15 values may be useful metrics of changes to these connections. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
15N, black spruce, denitrifier method, dissolved organic nitrogen, ectomycorrhiza, isotope fractionation, mixing models
in
Ecosystems
volume
15
issue
5
pages
819 - 831
publisher
Springer
external identifiers
  • wos:000306952400010
  • scopus:84864754599
ISSN
1432-9840
DOI
10.1007/s10021-012-9548-9
project
BECC
language
English
LU publication?
yes
id
261db4bd-e0e7-49c1-87a8-330cb3aeb437 (old id 3076488)
date added to LUP
2012-09-25 14:56:30
date last changed
2017-03-19 03:47:03
@article{261db4bd-e0e7-49c1-87a8-330cb3aeb437,
  abstract     = {Global patterns in soil, plant, and fungal stable isotopes of N (delta N-15) show promise as integrated metrics of N cycling, particularly the activity of ectomycorrhizal (ECM) fungi. At small spatial scales, however, it remains difficult to differentiate the underlying causes of plant delta N-15 variability and this limits the application of such measurements to better understand N cycling. We conducted a landscape-scale analysis of delta N-15 values from 31 putatively N-limited monospecific black spruce (Picea mariana) stands in central Alaska to assess the two main hypothesized sources of plant delta N-15 variation: differing sources and ECM fractionation. We found roughly 20% of the variability in black spruce foliar N and delta N-15 values to be correlated with the concentration and delta N-15 values of soil NH4 (+) and dissolved organic N (DON) pools, respectively. However, N-15-based mixing models from 24 of the stands suggested that fractionation by ECM fungi obscures the N-15 signature of soil N pools. Models, regressions, and N abundance data all suggested that increasing dependence on soil DON to meet black spruce growth demands predicates increasing reliance on ECM-derived N and that black spruce, on average, received 53% of its N from ECM fungi. Future research should partition the delta N-15 values within the soil DON pool to determine how choice of soil delta N-15 values influence modeled ECM activity. The C balance of boreal forests is tightly linked to N cycling and delta N-15 values may be useful metrics of changes to these connections.},
  author       = {Mayor, Jordan R. and Schuur, Edward A. G. and Mack, Michelle C. and Hollingsworth, Terresa N. and Bååth, Erland},
  issn         = {1432-9840},
  keyword      = {15N,black spruce,denitrifier method,dissolved organic nitrogen,ectomycorrhiza,isotope fractionation,mixing models},
  language     = {eng},
  number       = {5},
  pages        = {819--831},
  publisher    = {Springer},
  series       = {Ecosystems},
  title        = {Nitrogen Isotope Patterns in Alaskan Black Spruce Reflect Organic Nitrogen Sources and the Activity of Ectomycorrhizal Fungi},
  url          = {http://dx.doi.org/10.1007/s10021-012-9548-9},
  volume       = {15},
  year         = {2012},
}