Spatiotemporal variability in methane emission from an Arctic fen over a growing season : dynamics and driving factors
(2014) In Student thesis INES NGEM01 20132Dept of Physical Geography and Ecosystem Science
- Abstract (Danish)
- Resume. Metanudledning fra Nordlige vådområder udgør en betydelig del af den naturlige udledning af metan, en potent drivhusgas. Både fysiske og biologiske faktorer influerer produktion, oxidation og transport af metan og dermed netto udledningen. Udledningen af metan fra Nordlige vådområder viser stor rumlig og tidslig variation. Eftersom mange faktorer indvirker på udledningen af metan er viden om disses karakteristika og indbyrdes forhold nødvendig for at forstå hvordan miljømæssige ændringer vil påvirke den naturlige metanudledning. I dette studie vil den rumlige variation i metanudledningen bliver undersøgt mellem 10 plot (0.6 x 0.6 m), som er placeret på en ’fugtig til våd’ gradient nær randen af et høj-Arktisk kær. Udledningen blev... (More)
- Resume. Metanudledning fra Nordlige vådområder udgør en betydelig del af den naturlige udledning af metan, en potent drivhusgas. Både fysiske og biologiske faktorer influerer produktion, oxidation og transport af metan og dermed netto udledningen. Udledningen af metan fra Nordlige vådområder viser stor rumlig og tidslig variation. Eftersom mange faktorer indvirker på udledningen af metan er viden om disses karakteristika og indbyrdes forhold nødvendig for at forstå hvordan miljømæssige ændringer vil påvirke den naturlige metanudledning. I dette studie vil den rumlige variation i metanudledningen bliver undersøgt mellem 10 plot (0.6 x 0.6 m), som er placeret på en ’fugtig til våd’ gradient nær randen af et høj-Arktisk kær. Udledningen blev målt i vækstsæsonen 2013 og varierede både rumligt (med op til en faktor 10 mellem de to fjerneste plot) og sæsonmæssigt. Vækstsæsonen bestod af to ’peaks’ af sammenlignelig størrelse i metanudledning. Den gennemsnitlige sæsonmæssige udledning var relativ lav sammenlignet med tidligere år og andre studier fra circumpolare regioner og netto optaget af kuldioxid var lavt, med netto udledningen i store dele af sæsonen. Dette tilskrives hovedsagligt den meget lave mængde af vinternedbør, de tidlige snefrie forhold og en efterfølgende usædvanlig tør vækstsæson. Den sæsonmæssige udvikling i metanudledningen korrelerede særdeles godt med de fysiske parametre; jordtemperatur, vandstand og aktiv lag, på trods af at karakteren af deres indvirken på metanproduktionen er forskellig. I den våde del af gradienten var metanudledningen desuden negativt korreleret med netto udledningen af kuldioxid. Det faktum at alle disse korrelationer var stærke, fremhæver den store grad af autokorrelation mellem parametrene og deres lighed i forhold til den sæsonmæssige udvikling. Densiteten og sammensætningen af karplanter har tilsyneladende en dominerende rolle i forhold til størrelsesordenen af metanudledningen. Analyser af organiske syre og opløst organisk stof viste intet ensartet mønster med hensyn til placering på gradienten. Såkaldte ’ekstreme’ metanudledninger i den sidste halvdel af vækstsæsonen blev undersøgt separat, men ingen atmosfæriske parametre, såsom vindhastighed, ændring i lufttryk eller temperatur viste korrelationer med disse events. For de relativt tørre plot på gradienten udgjorde disse events op mod 25 % af udledningen og kan altså i randområderne af kær udgøre en betydelig del af den sæsonmæssige udledning. Ingen events blev målt fra de ’vådeste’ plot. Dette studie belyser vigtigheden af integrerede studier af de parametre der er styrende for metanudledningen, da både de fysiske og biologiske parametre ofte er afhængige og udviser de samme sæsonmæssige mønstre. (Less)
- Abstract
- Methane emissions from Northern wetlands constitute a substantial part of the total natural emission of methane, a strong greenhouse gas. Both environmental and biotic factors influence the production, oxidation and transport of methane and hence its net flux. The methane emission from Northern wetlands is highly variable both spatially and temporally. As many factors influence the methane flux, knowledge about the interrelation and character of these factors is needed in order to comprehend how environmental changes will affect natural methane emissions.
Here the small scale variability in methane emission is investigated using ten plots on a ‘moist to wet’ gradient, from the fringe towards the central part of a high-Arctic fen. The... (More) - Methane emissions from Northern wetlands constitute a substantial part of the total natural emission of methane, a strong greenhouse gas. Both environmental and biotic factors influence the production, oxidation and transport of methane and hence its net flux. The methane emission from Northern wetlands is highly variable both spatially and temporally. As many factors influence the methane flux, knowledge about the interrelation and character of these factors is needed in order to comprehend how environmental changes will affect natural methane emissions.
Here the small scale variability in methane emission is investigated using ten plots on a ‘moist to wet’ gradient, from the fringe towards the central part of a high-Arctic fen. The fluxes were measured during the growing season of 2013 and varied greatly both spatially (with up to a factor ten between the relatively dry and wet plots) and seasonally. The growing season had two peaks of comparable size. The mean growing season emission of methane was relatively low compared to previous years and other circumpolar sites and the uptake of CO2 was small and turned into a loss for the most of the growing season. This was mainly ascribed the unprecedented low amount of snowfall, early snowmelt and subsequent dry growing season conditions.
The seasonal development in methane emission was found to correlate very well with the environmental parameters; soil temperature, water level and active layer, although the character of the causal relationships are different. In the wetter part of the gradient the methane flux was also significantly correlated with the net ecosystem exchange. These strong correlations accentuate the autocorrelation and seasonality in these driving factors. Density of vascular plants and species composition appear to play a pivotal role in relation to the magnitude of the methane fluxes. Qualitative analysis of organic acids and dissolved organic carbon did not show any uniform pattern with regards to the location on the moisture gradient.
So-called extreme emission events were investigated separately and no correlations with atmospheric variables like wind speed, air pressure, air temperature or changes within these were found. These events were found to constitute up to 25 % of the seasonal methane emission from the relatively dry plots (no extreme events were detected from the ‘wettest’ plots) and hence constitute a rather significant portion of annual emissions.
This study qualitatively highlights the importance of studying controls on methane emission in an integrative manner, as both environmental and biotic controls are interrelated and often display the same seasonal patterns. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/4280464
- author
- Skov, Kirstine LU
- supervisor
-
- Magnus Lund LU
- Lena Ström LU
- Mikhail Mastepanov LU
- organization
- course
- NGEM01 20132
- year
- 2014
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- seasonal variability, Arctic wetlands, physical geography, methane emission, biological factors., geography, ebullition, environmental factors, spatial variability
- publication/series
- Student thesis INES
- report number
- 296
- language
- English
- id
- 4280464
- date added to LUP
- 2014-02-02 22:04:30
- date last changed
- 2014-02-02 22:04:30
@misc{4280464,
abstract = {{Methane emissions from Northern wetlands constitute a substantial part of the total natural emission of methane, a strong greenhouse gas. Both environmental and biotic factors influence the production, oxidation and transport of methane and hence its net flux. The methane emission from Northern wetlands is highly variable both spatially and temporally. As many factors influence the methane flux, knowledge about the interrelation and character of these factors is needed in order to comprehend how environmental changes will affect natural methane emissions.
Here the small scale variability in methane emission is investigated using ten plots on a ‘moist to wet’ gradient, from the fringe towards the central part of a high-Arctic fen. The fluxes were measured during the growing season of 2013 and varied greatly both spatially (with up to a factor ten between the relatively dry and wet plots) and seasonally. The growing season had two peaks of comparable size. The mean growing season emission of methane was relatively low compared to previous years and other circumpolar sites and the uptake of CO2 was small and turned into a loss for the most of the growing season. This was mainly ascribed the unprecedented low amount of snowfall, early snowmelt and subsequent dry growing season conditions.
The seasonal development in methane emission was found to correlate very well with the environmental parameters; soil temperature, water level and active layer, although the character of the causal relationships are different. In the wetter part of the gradient the methane flux was also significantly correlated with the net ecosystem exchange. These strong correlations accentuate the autocorrelation and seasonality in these driving factors. Density of vascular plants and species composition appear to play a pivotal role in relation to the magnitude of the methane fluxes. Qualitative analysis of organic acids and dissolved organic carbon did not show any uniform pattern with regards to the location on the moisture gradient.
So-called extreme emission events were investigated separately and no correlations with atmospheric variables like wind speed, air pressure, air temperature or changes within these were found. These events were found to constitute up to 25 % of the seasonal methane emission from the relatively dry plots (no extreme events were detected from the ‘wettest’ plots) and hence constitute a rather significant portion of annual emissions.
This study qualitatively highlights the importance of studying controls on methane emission in an integrative manner, as both environmental and biotic controls are interrelated and often display the same seasonal patterns.}},
author = {{Skov, Kirstine}},
language = {{eng}},
note = {{Student Paper}},
series = {{Student thesis INES}},
title = {{Spatiotemporal variability in methane emission from an Arctic fen over a growing season : dynamics and driving factors}},
year = {{2014}},
}