Micrometeorological measurements of methane and nitrous oxide exchange above a boreal aspen forest

Simpson, Isobel J.; Edwards, Grant C.; Thurtell, G. W.; Hartog, G. Den; Neumann, H. H.; Staebler, R. M.

doi:10.1029/97jd03181

Cited by 72 publications

(60 citation statements)

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“…The 26 m H 2 gradients were often close to the precision of the GC-HePDD system, especially during turbulent daytime periods. As a result, raw measurements were averaged to reveal the environmental gradients and fluxes, as has been previously required for these types of measurements above the forest canopy (Simpson et al, 1997). For example, the 26 and 2 m gradients of H 2 and CO 2 averaged into 2 h bins for the month of July clearly showed the underlying environmental signal (Fig.…”

Section: Gradient Measurementsmentioning

confidence: 99%

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Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

et al. 2014

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Abstract. Our understanding of biosphere-atmosphere exchange has been considerably enhanced by eddy covariance measurements. However, there remain many trace gases, such as molecular hydrogen (H 2 ), that lack suitable analytical methods to measure their fluxes by eddy covariance. In such cases, flux-gradient methods can be used to calculate ecosystem-scale fluxes from vertical concentration gradients. The budget of atmospheric H 2 is poorly constrained by the limited available observations, and thus the ability to quantify and characterize the sources and sinks of H 2 by fluxgradient methods in various ecosystems is important. We developed an approach to make nonintrusive, automated measurements of ecosystem-scale H 2 fluxes both above and below the forest canopy at the Harvard Forest in Petersham, Massachusetts, for over a year. We used three flux-gradient methods to calculate the fluxes: two similarity methods that do not rely on a micrometeorological determination of the eddy diffusivity, K, based on (1) trace gases or (2) sensible heat, and one flux-gradient method that (3) parameterizes K. We quantitatively assessed the flux-gradient methods using CO 2 and H 2 O by comparison to their simultaneous independent flux measurements via eddy covariance and soil chambers. All three flux-gradient methods performed well in certain locations, seasons, and times of day, and the best methods were trace gas similarity for above the canopy and K parameterization below it. Sensible heat similarity required several independent measurements, and the results were more variable, in part because those data were only available in the winter, when heat fluxes and temperature gradients were small and difficult to measure. Biases were often observed between flux-gradient methods and the independent flux measurements, and there was at least a 26 % difference in nocturnal eddy-derived net ecosystem exchange (NEE) and chamber measurements. H 2 fluxes calculated in a summer period agreed within their uncertainty and pointed to soil uptake as the main driver of H 2 exchange at Harvard Forest, with H 2 deposition velocities ranging from 0.04 to 0.10 cm s −1 .

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Section: Gradient Measurementsmentioning

confidence: 99%

“…(22a) and (22b) in Foken (2006). The method has been applied close to the surface (Fritsche et al, 2008) and above the forest canopy (Simpson et al, 1997(Simpson et al, , 1998. In this study, the K parameterization method was applied below the canopy.…”

Section: K Parameterizationmentioning

confidence: 99%

Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

et al. 2014

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“…мере определяющая измеренную величину общего потока, например, 90% этого потока ("…footprint, i. e., the area contributing by percentage, e. g., 90% of the total flux"). Подробное рассмотрение теории футпринта и конкретные модели для него см., например, в [36][37][38][39][40][41], причем в работе [36] даны ссылки еще на 22 конкретные модели футпринта.…”

Section: область влияния (футпринт)unclassified

Determination of Gas Exchange on the Border Between Ecosystem and Atmosphere: Inverse Modeling

Glagolev¹

2012

Math.Biol.Bioinf.

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Аннотация. Предложена методика получения данных, необходимых для определения удельного потока газа из почвы методом обратной задачи. По этой методике проведены измерения потока метана в олиготрофном болоте подзоны средней тайги. Определённые посредством предлагаемого метода значения удельного потока (1.5-3 мгС-СН 4 ·м -2 ·ч -1 ) оказались вполне сопоставимы с результатами измерений методом статических камер, проведённых на этом же объекте. Определена область влияния («футпринт»): её величина варьирует от первых сотен метров (в условиях неустойчивой стратификации атмосферы) до нескольких тысяч метров (в условиях сильно устойчивой стратификации). Даже с учётом погрешности метода и погрешностей, вносимых изменением футпринта в течение суточных наблюдений, предлагаемый способ позволил между двумя сериями измерений выявить различия удельного потока, которые, вероятно, возникли из-за природной динамики таких факторов эмиссии метана, как уровень болотных вод и температура поверхностного слоя почвы. Ключевые слова: микрометеорологические методы, метод обратной задачи, поток газа из почвы, метан. ВВЕДЕНИЕГазообмен на границе экосистема/атмосфера играет в экологии чрезвычайно важную роль. Например, Карелин и Замолодчиков [1] указывают, что с биологическим круговоротом углерода почти полностью отождествляются такие термины и понятия, как валовая первичная продуктивность, чистая первичная продуктивность, валовое дыхание, чистая экосистемная продуктивность -все они основаны на измерении потоков СО 2 . В связи с глобальным потеплением климата Земли ведется детальное изучение источников эмиссии газов, приводящих к парниковому эффекту [2]. В дальнейшем мы ограничиваемся только примером определения удельного потока метана с поверхности болота. Однако следует подчеркнуть, что рассматриваемый в данной работе метод применим для измерения эмиссии (или поглощения) любой атмосферной примеси и практически для любого типа как природных (например, луг или болото), так и антропогенных (например, полигон захоронения твёрдых бытовых отходов) экосистем.

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“…Because this method does not required a gas analyzer with a rapid response, unlike the EC method, it has begun to attract considerable attention for use in studies of trace gas fluxes (Simpson et al 1997;Nemitz et al 2001). An REA system was previously developed by our group (Hamotani et al 1996(Hamotani et al , 2001, and its precision and accuracy have been validated (Ueyama et al 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Previously, this method was applied in ecosystems that represented well-known methane sources, such as rice paddies (Miyata et al 2000;Takimoto et al 2010), natural wetlands (Friborg and Christensen 1997;Simpson et al 1997;Werner et al 2003;Rinne et al 2007), and tundra Wille et al 2008). However, relatively few studies have been conducted in forest ecosystems (Ueyama et al 2006;Smeets et al 2009), probably because the measurements of small methane uptakes is much more difficult than the measurement of fluxes from large sources.…”

Section: Introductionmentioning

confidence: 99%

Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method

Ueyama

Hamotani

Nishimura

et al. 2012

Theor Appl Climatol

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We measured the methane flux of a forest canopy throughout a year using a relaxed eddy accumulation (REA) method. This sampling system was carefully validated against heat and CO 2 fluxes measured by the eddy covariance method. Although the sampling system was robust, there were large uncertainties in the measured methane fluxes because of the limited precision of the methane gas analyzer. Based on the spectral characteristics of signals from the methane analyzer and the diurnal variations in the standard deviation of the vertical wind velocity, we found the daytime and nighttime precision of halfhourly methane flux measurements to be approximately 1.2 and 0.7 μg CH 4 m −2 s −1 , respectively. Additional uncertainties caused by the dilution effect were estimated to affect the accuracy by as much as 0.21 μg CH 4 m −2 s −1 on a half-hourly basis. Diurnal and seasonal variations were observed in the measured fluxes. The biological emission from plant leaves was not observed in our studies, and thus could be negligible at the canopy-scale exchange. The annual methane sink was 835±175 mg CH 4 m −2 year −1 (8.35 kg CH 4 ha −1 year −1 ), which was comparable to the flux range of 379-2,478 mg CH 4 m −2 year −1 previously measured in other Japanese forest soils. This study indicated that the REA method could be a promising technique to measure canopy scale methane fluxes over forests, but further improvement of precision of the analyzer will be required.

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Micrometeorological measurements of methane and nitrous oxide exchange above a boreal aspen forest

Cited by 72 publications

References 50 publications

Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

Determination of Gas Exchange on the Border Between Ecosystem and Atmosphere: Inverse Modeling

Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method

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