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| Titel |
Effects of ploughing on land-atmosphere exchange of greenhouse gases in a managed temperate grassland in central Scotland |
| VerfasserIn |
Carole Helfter, Julia Drewer, Margaret Anderson, Bob Scholtes, Bob Rees, Ute Skiba |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106351
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| Publikation (Nr.) |
 EGU/EGU2015-6017.pdf |
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| Zusammenfassung |
| Grasslands are important ecosystems covering > 20% and > 30% of EU and Scotland’s land
area respectively. Management practices such as grazing, fertilisation and ploughing can have
significant short- and long-term effects on greenhouse gas exchange. Here we report on two
separate ploughing events two years apart in adjacent grasslands under common
management.
The Easter Bush grassland, located 10 km south of Edinburgh (55Ë 52’N, 3Ë 2’W),
comprises two fields separated by a fence and is used for grazing by sheep and cattle. The
vegetation is predominantly Lolium perenne (> 90%) growing on poorly drained clay loam.
The fields receive several applications of mineral fertiliser a year in spring and summer. Net
ecosystem exchange (NEE) of carbon dioxide (CO2) has been monitored continuously by
eddy-covariance (EC) since 2002 which has demonstrated that the site is a consistent yet
variable sink of atmospheric CO2. The EC system comprises a LI-COR 7000 closed-path
analyser and a Gill Instruments Windmaster Pro ultrasonic anemometer mounted atop a 2.5
m mast located along the fence line separating the fields. In addition, fluxes of
nitrous oxide (N2O), methane (CH4)and CO2were measured with static chambers
installed along transects in each field. Gas samples collected from the chambers were
analysed by gas chromatography and fluxes calculated for each 60-minute sampling
period.
The ploughing events in 2012 and 2014 exhibited multiple similarities in terms of NEE.
The light response (i.e. relationship between CO2 flux, and photosynthetically active
radiation, PAR) of the NF and SF during the month preceding each ploughing event was of
comparable magnitude in both years. Following ploughing, CO2 uptake ceased in the
ploughed field for approximately one month and full recovery of the photosynthetic potential
was observed after ca. 2 months. During the month following the 2014 ploughing
event, the ploughed NF released on average 333 ± 17 mg CO2-C m-2 h-1. In
contrast, the SF net uptake during the same period was -79 ± 19 mg CO2-C m-2 h-1.
Ploughing caused a net release of carbon of 183 g CO2-C m-2 during the month
following ploughing, thus turning the grassland into a potent CO2 source. Chamber
measurements of CH4 and N2O exhibited high spatial variability in 2012 and no statistical
difference could be established between fields and treatments. CH4 fluxes were high in
both fields after ploughing which was presumably linked to air temperature. N2O
fluxes in the ploughed SF reached on average 100 μg N2O-N m-2 h-1 29 days after
ploughing which corresponded to ca. 20 times the background level recorded at the
site. Fluxes of N2O were however considerably larger in 2014, peaking at 2570
μg N2O-N m-2 h-1 29 days after ploughing. Contrarily to 2012, substantial and
statistically significant CH4 emissions were recorded in 2014 in the ploughed field.
Whilst spatial variability was high in both years it can nevertheless be concluded
that ploughing had substantial adverse short term effects on emissions and that
environmental conditions greatly impacted the magnitude of CH4 and N2O fluxes. |
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