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Nitrogen dynamics in contrasting forest ecosystems exposed to enhanced atmospheric N deposition

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Abstract
Despite chronically enhanced nitrogen (N) deposition to forest ecosystems in Europe and NE America, considerable N retention by forests has been observed. It is still unclear which factors determine N retention in forest soils. However, this knowledge is crucial to assess the impact of changing anthropogenic N emissions on future N cycling and N loss of forests. For coniferous and deciduous forest stands at comparable sites, it is known that both N deposition to the forest floor as well as N loss by leaching below the rooting zone are significantly higher in coniferous stands (De Schrijver et al., 2007). In addition, the N loss in coniferous stands is often more enhanced than can be explained by the higher N input only, which suggests lower N retention by coniferous stands and may be related to differences in litter quality, microbial activity, and N uptake by plant roots. To test this hypothesis, we studied the effect of forest type on N retention. N dynamics were examined for two adjacent forest stands (pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.)) on a well-drained soil type and with a similar stand history, which are located in a region with high N deposition (Belgium). Firstly, input-output N budgets were established by quantifying atmospheric deposition and leaching, which confirmed the above finding of higher N deposition and disproportionately higher N loss by the pine stand than the oak stand. Secondly, the fate of inorganic N within the ecosystems was studied by spraying dissolved 15N onto the forest floor, both as ammonium (NH4+) and nitrate (NO3-). The 15N recovery over time in organic and mineral soil layers, tree roots, water leaching, ferns, foliage, and stem wood was compared between the two forest stands and N treatments. Thirdly, in situ gross N transformation rates in undisturbed mineral forest soils were determined via a 15N tracing approach (Müller et al., 2007). Meaningful differences between the two forest stands were found for the rates of mineralisation, heterotrophic and autotrophic nitrification, and NH4+ and NO3- immobilisation. Unexpectedly, dissimilatory NO3- reduction to NH4+ (DNRA) was detected in the oak soil. This process has mainly been described for unpolluted soils (e.g., Huygens et al., 2008), and to the best of our knowledge, this is the first report of DNRA under field conditions in a temperate forest soil under high N deposition.

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Chicago
Staelens, Jeroen, Tobias Rütting, Dries Huygens, An De Schrijver, Christoph Müller, Kris Verheyen, and Pascal Boeckx. 2009. “Nitrogen Dynamics in Contrasting Forest Ecosystems Exposed to Enhanced Atmospheric N Deposition.” In Working Papers of the Finnish Forest Research Institute, ed. Liisa Ukonmaanaho, Tiina M Nieminen, and Mike Starr, 128:220–220. Vantaa, Finland: Finnish Forest Research Institute.
APA
Staelens, Jeroen, Rütting, T., Huygens, D., De Schrijver, A., Müller, C., Verheyen, K., & Boeckx, P. (2009). Nitrogen dynamics in contrasting forest ecosystems exposed to enhanced atmospheric N deposition. In L. Ukonmaanaho, T. M. Nieminen, & M. Starr (Eds.), Working papers of the Finnish Forest Research Institute (Vol. 128, pp. 220–220). Presented at the 6th International symposium on Ecosystem Behaviour BIOGEOMON 2009, Vantaa, Finland: Finnish Forest Research Institute.
Vancouver
1.
Staelens J, Rütting T, Huygens D, De Schrijver A, Müller C, Verheyen K, et al. Nitrogen dynamics in contrasting forest ecosystems exposed to enhanced atmospheric N deposition. In: Ukonmaanaho L, Nieminen TM, Starr M, editors. Working papers of the Finnish Forest Research Institute. Vantaa, Finland: Finnish Forest Research Institute; 2009. p. 220–220.
MLA
Staelens, Jeroen, Tobias Rütting, Dries Huygens, et al. “Nitrogen Dynamics in Contrasting Forest Ecosystems Exposed to Enhanced Atmospheric N Deposition.” Working Papers of the Finnish Forest Research Institute. Ed. Liisa Ukonmaanaho, Tiina M Nieminen, & Mike Starr. Vol. 128. Vantaa, Finland: Finnish Forest Research Institute, 2009. 220–220. Print.
@inproceedings{1165770,
  abstract     = {Despite chronically enhanced nitrogen (N) deposition to forest ecosystems in Europe and NE America, considerable N retention by forests has been observed. It is still unclear which factors determine N retention in forest soils. However, this knowledge is crucial to assess the impact of changing anthropogenic N emissions on future N cycling and N loss of forests. For coniferous and deciduous forest stands at comparable sites, it is known that both N deposition to the forest floor as well as N loss by leaching below the rooting zone are significantly higher in coniferous stands (De Schrijver et al., 2007). In addition, the N loss in coniferous stands is often more enhanced than can be explained by the higher N input only, which suggests lower N retention by coniferous stands and may be related to differences in litter quality, microbial activity, and N uptake by plant roots. To test this hypothesis, we studied the effect of forest type on N retention. N dynamics were examined for two adjacent forest stands (pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.)) on a well-drained soil type and with a similar stand history, which are located in a region with high N deposition (Belgium). Firstly, input-output N budgets were established by quantifying atmospheric deposition and leaching, which confirmed the above finding of higher N deposition and disproportionately higher N loss by the pine stand than the oak stand. Secondly, the fate of inorganic N within the ecosystems was studied by spraying dissolved 15N onto the forest floor, both as ammonium (NH4+) and nitrate (NO3-). The 15N recovery over time in organic and mineral soil layers, tree roots, water leaching, ferns, foliage, and stem wood was compared between the two forest stands and N treatments. Thirdly, in situ gross N transformation rates in undisturbed mineral forest soils were determined via a 15N tracing approach (M{\"u}ller et al., 2007). Meaningful differences between the two forest stands were found for the rates of mineralisation, heterotrophic and autotrophic nitrification, and NH4+ and NO3- immobilisation. Unexpectedly, dissimilatory NO3- reduction to NH4+ (DNRA) was detected in the oak soil. This process has mainly been described for unpolluted soils (e.g., Huygens et al., 2008), and to the best of our knowledge, this is the first report of DNRA under field conditions in a temperate forest soil under high N deposition.},
  author       = {Staelens, Jeroen and R{\"u}tting, Tobias and Huygens, Dries and De Schrijver, An and M{\"u}ller, Christoph and Verheyen, Kris and Boeckx, Pascal},
  booktitle    = {Working papers of the Finnish Forest Research Institute},
  editor       = {Ukonmaanaho, Liisa and Nieminen, Tiina M and Starr, Mike},
  isbn         = {9789514021763},
  issn         = {1795-150X},
  language     = {eng},
  location     = {Helsinki, Finland},
  pages        = {220--220},
  publisher    = {Finnish Forest Research Institute},
  title        = {Nitrogen dynamics in contrasting forest ecosystems exposed to enhanced atmospheric N deposition},
  url          = {http://www.metla.fi/julkaisut/workingpapers/2009/mwp128.pdf},
  volume       = {128},
  year         = {2009},
}