Change search
ReferencesLink to record
Permanent link

Direct link
Can small-scale experiments predict ecosystem responses?: An example from peatlands
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Show others and affiliations
2009 (English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, no 3, 449-456 p.Article in journal (Refereed) Published
Abstract [en]

Oligotrophic, Sphagnum-dominated peatlands have been regarded as long-term stable ecosystems that function as carbon sinks. As a result of environmental perturbations, particularly anthropogenic N deposition, this view is now increasingly questioned. We examined whether small-scale field experiments can predict the direction and magnitude of ecosystem responses to increased N supply. We, therefore, compared data from a 10-year field experiment (involving deposition of 2, 15 and 30 kg N ha−1 year−1) with data from a gradient associated with increased N deposition (2, 8 and 12 kg N ha−1 year−1). We chose to compare: (1) the physiological response of Sphagnumbalticum, measured in the form of N accumulation as free amino acids (NAA); and (2) changes in the total Sphagnum cover, the cover of S. balticum, and vascular plant cover. In all cases we found a highly significant correlation between the two data sets. We attribute the high correspondence between the two data sets to the key function of the dominant group of organisms, the Sphagna, that monopolize N availability and control the water balance, creating an environment hostile to vascular plants. Thus the key role of Sphagna as ecosystem engineers seems to supersede the role of other, scale-dependent processes. We also conclude that NAA is a sensitive indicator that can be used to signal the slow and gradual shift from Sphagnum to vascular plant dominance.

Place, publisher, year, edition, pages
2009. Vol. 118, no 3, 449-456 p.
URN: urn:nbn:se:umu:diva-23292DOI: 10.1111/j.1600-0706.2008.17129.xOAI: diva2:222698
Available from: 2009-06-09 Created: 2009-06-09 Last updated: 2016-02-08Bibliographically approved
In thesis
1. Responses of peatland vegetation to enhanced nitrogen
Open this publication in new window or tab >>Responses of peatland vegetation to enhanced nitrogen
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human alteration of the global nitrogen (N) cycle has had major impacts on naturally N-limited ecosystems worldwide. Peatlands, dominated by peat mosses, Sphagnum species, represent one such sensitive ecosystem. I have studied how this ecosystem is affected by increased N availability, using a small-scale N fertilization experiment in combination with a gradient study of three peatlands with varying N deposition.

I found both in the experiment and in the gradient a similar pattern of Sphagnum decline accompanied by an increase of vascular plants associated with enhanced N supply. For one common Sphagnum species - both in the experiment and in the gradient study - I also found an identical, linear increase in soluble amino acid N (NAA) accumulation. As soluble amino acids function as N storage compounds among Sphagna, NAA is a suitable measure for Sphagnum N status, and indicates accumulation of excess N not used for growth. My results show that NAA can be used as a sensitive indicator to signal N pollution before the slow, and gradual, regime shift from Sphagnum to vascular plant dominance is visible. In an N-uptake experiment using Sphagnum specimens from the three peatlands varying in N deposition, I found a reduced N-uptake by both investigated Sphagnum species from a high N deposition site, in south-western Sweden. This potential of Sphagna to adjust to high N loads through N uptake regulation will, however, not prevent tissue N accumulation, and as a result a shift from Sphagnum to vascular plant dominance.

In general I found similar patterns of N induced changes both in Sphagnum tissue chemistry and vegetation structure in the experiment and along the gradient study. Thus, I conclude that long-term, small-scale field experiments seem to offer reliable estimates of both the direction and strength of key vegetation responses in Sphagnum dominated peatlands. This is likely related to the key role of Sphagna as ecosystem engineers.

In the experiment I found a marked time lag in vegetation response to N application treatments. The closed Sphagnum carpet did not collapse until after eight years of continuous treatments. Another result was that dwarf shrubs, e.g. cranberry Vaccinium oxycoccos, first increased, but later declined due to severe attacks by fungal diseases. One important conclusion is that long-term, manipulative field experiments are necessary for our ability to understand how ecosystems will respond to environmental change.

Place, publisher, year, edition, pages
Umeå: Ekologi, miljö och geovetenskap, 2008. 24 p.
Sphagnum, nitrogen, peatlands, soluble amino acids, gradient study, field experiment
National Category
Biological Sciences
urn:nbn:se:umu:diva-1655 (URN)978-91-7264-551-6 (ISBN)
Public defence
2008-06-05, Lilla Hörsalen, KBC, SE-90187, Umeå, 10:00 (English)
Available from: 2008-05-15 Created: 2008-05-15 Last updated: 2016-02-08Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Wiedermann, Magdalena MEricson, Lars
By organisation
Department of Ecology and Environmental Sciences
In the same journal

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 101 hits
ReferencesLink to record
Permanent link

Direct link