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| Titel |
Soil, plant, and transport influences on methane in a subalpine forest under high ultraviolet irradiance |
| VerfasserIn |
D. R. Bowling, J. B. Miller, M. E. Rhodes, S. P. Burns, R. K. Monson, D. Baer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 7 ; Nr. 6, no. 7 (2009-07-30), S.1311-1324 |
| Datensatznummer |
250003915
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| Publikation (Nr.) |
 copernicus.org/bg-6-1311-2009.pdf |
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| Zusammenfassung |
| Recent studies have demonstrated direct methane emission from plant foliage
under aerobic conditions, particularly under high ultraviolet (UV)
irradiance. We examined the potential importance of this phenomenon in a
high-elevation conifer forest using micrometeorological techniques. Vertical
profiles of methane and carbon dioxide in forest air were monitored every 2 h for 6 weeks
in summer 2007. Day to day variability in above-canopy
CH4 was high, with observed values in the range 1790 to 1910 nmol mol−1. High CH4 was correlated with high carbon monoxide and
related to wind direction, consistent with pollutant transport from an urban
area by a well-studied mountain-plain wind system. Soils were
moderately dry during the study. Vertical gradients of CH4 were small
but detectable day and night, both near the ground and within the vegetation
canopy. Gradients near the ground were consistent with the forest soil being
a net CH4 sink. Using scalar similarity with CO2, the magnitude of
the summer soil CH4 sink was estimated at ~1.7 mg CH4 m−2 h−1,
which is similar to other temperate forest upland soils.
The high-elevation forest was naturally exposed to high UV irradiance under
clear sky conditions, with observed peak UVB irradiance >2 W m−2.
Gradients and means of CO2 within the canopy under daytime conditions
showed net uptake of CO2 due to photosynthetic drawdown as expected. No
evidence was found for a significant foliar CH4 source in the
vegetation canopy, even under high UV conditions. While the possibility of a
weak foliar source cannot be excluded given the observed soil sink, overall
this subalpine forest was a net sink for atmospheric methane during the
growing season. |
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