 |
| Titel |
Impact of simulated atmospheric nitrogen deposition on nutrient cycling and carbon sink via mycorrhizal fungi in two nutrient-poor peatlands |
| VerfasserIn |
Tuula Larmola, Heikki Kiheri, Jill L. Bubier, Netty van Dijk, Nancy Dise, Hannu Fritze, Erik A. Hobbie, Sari Juutinen, Raija Laiho, Tim R. Moore, Taina Pennanen |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250139864
|
| Publikation (Nr.) |
 EGU/EGU2017-3179.pdf |
|
|
|
|
|
| Zusammenfassung |
| Peatlands store one third of the global soil carbon (C) pool. Long-term fertilization
experiments in nutrient-poor peatlands showed that simulated atmospheric nitrogen (N)
deposition does not enhance ecosystem C uptake but reduces C sink potential. Recent
studies have shown that a significant proportion of C input to soil in low-fertility
forests entered the soil through mycorrhizal fungi, rather than as plant litter. Is
atmospheric N deposition diminishing peatland C sink potential due to the suppression of
ericoid mycorrhizal fungi? We studied how nutrient addition influences plant biomass
allocation and the extent to which plants rely on mycorrhizal N uptake at two of the
longest-running nutrient addition experiments on peatlands, Whim Bog, United
Kingdom, and Mer Bleue Bog, Canada. We determined the peak growing season
aboveground biomass production and coverage of vascular plants using the point intercept
method. We also analyzed isotopic δ15N patterns and nutrient contents in leaves of
dominant ericoid mycorrhizal shrubs as well as the non-mycorrhizal sedge Eriophorum
vaginatum under different nutrient addition treatments. The treatments receive an
additional load of 1.6-6.4 N g m−2 y−1 either as ammonium (NH4) nitrate (NO3)
or NH4NO3 and with or without phosphorus (P) and potassium (K), alongside
unfertilized controls. After 11-16 years of nutrient addition, the vegetation structure
had changed remarkably. Ten of the eleven nutrient addition treatments showed
an increase of up to 60% in total vascular plant abundance. Only three (NH4Cl,
NH4ClPK, NaNO3PK) of the nutrient addition treatments showed a concurrent
decrease of down to 50% in the relative proportion of ericoid mycorrhizal shrubs to
total vascular plant abundance. The response to nutrient load may be explained by
the water table depth, the form of N added and whether N was added with PK.
Shrubs were strong competitors at the dry Mer Bleue bog while sedges gained in
abundance at the wetter Whim bog. Our results also suggest that the impacts of
reduced and oxidized N on above ground biomass of ericoid shrubs differ and that
plants have become increasingly P limited under high simulated atmospheric N
deposition. Combined with mycorrhizal abundance and foliar isotopic δ15N patterns, the
data will allow us to estimate the extent to which plants rely on mycorrhizal N
uptake and whether mycorrhizal responses are linked to diminished C sink potential.
This evidence is needed to establish critical loads for C sink potential in peatlands. |
|
|
|
|
|
|