 |
| Titel |
The effect of anaerobicity and temperature on N2 and N2O dynamics in forestry drained boreal peat soils |
| VerfasserIn |
Mari Pihlatie, Isto Hongisto, Michael Dannenmann, Willibald Georg, Rainer Gasche, Klaus Butterbach-Bahl |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080060
|
|
|
|
|
|
| Zusammenfassung |
| Molecular nitrogen (N2) is the dominant end-product of microbial denitrification
in soils; however, due to difficulties in measuring N2 exchange, the emissions of
N2 from terrestrial ecosystems are largely unknown. In boreal peatland soils, the
combination of high soil carbon and nitrogen contents, fluctuating water-table and high
decomposition activity of the peat make these soils potentially large emitters of N
gases via microbial denitrification processes. This motivated us to quantify the N2
and nitrous oxide (N2O) losses from boreal drained peat soils varying in fertility
status.
Soil samples were collected from two drained peatland forests: a nutrient-rich (Lettosuo)
and a nutrient-poor (Kalevansuo) site, both located in the boreal zone of Southern
Finland. N2 and N2O emissions from intact soil cores were measured using the helium
gas flow soil core method. Two incubation experiments were conducted focusing
on the effects of anaerobicity and temperature on N2 and N2O dynamics of the
top-soil (experiment 1), and the effect of anaerobicity on N2 and N2O dynamics in the
peat profile (experiment 2). Soil samples in experiment 1 were incubated under 1)
cold (2Ë C) aerobic (20% O2, 80% He), 2) cold (2Ë C) anaerobic (0% O2, 100%
He), and 3) warm (15Ë C) anaerobic conditions, while those in experiment 2 were
incubated under 1) warm aerobic and 2) warm anaerobic conditions. Dynamics
of N2 and N2O fluxes for each incubation condition were followed until fluxes
stabilized.
In general, the N2 and N2O fluxes in the nutrient-rich Lettosuo peat were higher and more
variable than those at the nutrient-poor Kalevansuo peat. In the nutrient-rich Lettosuo, both
the N2 and N2O emissions increased dramatically after the change from aerobic to anaerobic
conditions, and again after the temperature rise from 2 to 15Ë C. This latter peak in
emissions was followed by a switch from N2O production to N2O consumption
and a simultaneous sharp decrease in N2 emissions. Although, the N2 and N2O
fluxes in the nutrient-poor Kalevansuo peat were small and close to the detection
limit, the change from the aerobic to anaerobic conditions induced significant N2O
uptake, which was even more pronounced under warm anaerobic conditions. At the
nutrient-rich Lettosuo, all the three soil layers (10-15 cm, 15-20 cm, 40-45 cm) were
equally active in N2 and N2O production or consumption. Overall, N2 emissions
from both sites always exceeded N2O emissions, and when the fluxes were positive
and above their detection limits, the ratio of N2:N2O ranged between 1 and 180. |
|
|
|
|
|
|