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| Titel |
Biotic, abiotic and management controls on methanol fluxes above a temperate mountain grassland |
| VerfasserIn |
Lukas Hörtnagl, Ines Bamberger, Martin Graus, Taina Ruuskanen, Ralf Schnitzhofer, Markus Müller, Armin Hansel, Georg Wohlfahrt |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035435
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| Zusammenfassung |
| It was previously hypothesised that (i) stomatal conductance and plant growth play a key role
in the emission of methanol (Hüve et al. 2007, Niinemets et al. 2004), (ii) methanol fluxes
increase with air temperature (Niinemets and Reichstein 2003), and (iii) during cutting (leaf
wounding) events and during drying high amounts of methanol are emitted into the
atmosphere (Davison et al. 2008).
Methanol fluxes were measured above a managed, temperate mountain grassland in
Stubai Valley (Tyrol, Austria) during two growing seasons (2008 and 2009). Half-hourly flux
values were calculated by means of the disjunct eddy covariance method using 3-dimensional
wind-data of a sonic anemometer and mixing ratios of methanol measured with a
proton-transfer-reaction-mass-spectrometer (PTR-MS). The surface conductance to water
vapour was derived from measured evapotranspiration by inverting the Penman-Monteith
combination equation (Wohlfahrt et al., 2009) for dry canopy conditions and used as a proxy
for canopyscale stomatal conductance.
Methanol fluxes exhibited a clear diurnal cycle with closetozero fluxes during nighttime
and emissions, up to 10 nmol m-2 s-1, which followed the diurnal course of radiation and air
temperature during daytime. Higher emissions of up to 30 nmol m-2 s-1were observed
during cut events and spreading of organic manure. Methanol fluxes showed positive
correlations with air temperature, stomatal conductance, and photosynthetically active
radiation (PAR), confirming previous studies (e.g. Niinemets and Reichstein 2003). All three
previously mentioned factors combined together were able to explain 40% of the
observed flux variability. The influence of rapid changes in stomatal conductance
on methanol fluxes, pointed out in earlier studies at the leaf-level (e.g. Niinemets
and Reichstein 2003), could not be confirmed on ecosystem scale, possibly due to
within-canopy gradients in stomatal conductance and the fact that fluxes were determined as
half-hourly averages. As methanol is produced in expanding cell walls, the change in the
measured green area index (ÎGAI) was used as a proxy for plant growth. However
ÎGAI was poorly correlated with methanol fluxes, possible explanations will be
discussed.
References:
Davison, B., Brunner, A., Amman, C., Spirig, C., Jocher, M., Neftel, A. Cut-induced
VOC emissions from agricultural grasslands. Plant Biol. 10, 76–85, 2008.
Harley, P., Greenberg, J., Niinemets, Ü., and Guenther, A..: Environmental controls over
methanol emission from leaves. Biogeosciences, 4, 1083–1099, 2007.
Hüve, K., Christ, M., Kleist, E., Uerlings, R., Niinemets, Ü., Walter, A. and Wildt, J.:
Simultaneous growth and emission measurements demonstrate an interactive control of
methanol release by leaf expansion and stomata. doi:10.1093/jxb/erm038, Journal of
Experimental Botany, 2007.
Niinemets, Ü. and Reichstein, M.: Controls on the emission of plant volatiles through
stomata: A sensitivity analysis. J. Geophys. Res., 108, 4211, doi:10.1029/2002JD002626,
2003.
Niinemets, Ü., Loreto, F. and Reichstein, M.: Physiological and physicochemical
controls on foliar volatile organic compound emissions. Trends in Plant Science,9,
2004.
Wohlfahrt G., Haslwanter A., Hörtnagl L., Jasoni R.L., Fenstermaker L.F., Arnone J.A.
III, Hammerle A. (2009) On the consequences of the energy imbalance for calculating
surface conductance to water vapour. Agricultural and Forest Meteorology 149, 15561559. |
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