Winter and summer nitrous oxide and nitrogen oxides fluxes from a seasonally snow-covered subalpine meadow at Niwot Ridge, Colorado

Filippa, Gianluca; Freppaz, Michèle; Williams, Mark W.; Helmig, Detlev; Liptzin, Daniel; Seok, B.; Hall, B. D.; Chowanski, Kurt

doi:10.1007/s10533-009-9304-1

Cited by 46 publications

(44 citation statements)

References 57 publications

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“…Furthermore, correlations were high for data from adjacent gradients (please see Fig. 4 in Filippa et al (2009), which graphically displays the corresponding analysis for calculated N 2 O fluxes from the 90-60 cm vs. the 60-30 cm gradient data), and became weaker the further the gradients were separated vertically. Also, better agreement was generally seen in data from the middle of the snowpack, whereas results from sampling near the bottom and involving measurements from the ambient inlet often showed weaker correlations.…”

Section: Co 2 Fluxesmentioning

confidence: 91%

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An automated system for continuous measurements of trace gas fluxes through snow: an evaluation of the gas diffusion method at a subalpine forest site, Niwot Ridge, Colorado

et al. 2009

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An experimental system for sampling trace gas fluxes through seasonal snowpack was deployed at a subalpine site near treeline at Niwot Ridge, Colorado. The sampling manifold was in place throughout the entire snow-covered season for continuous air sampling with minimal disturbance to the snowpack. A series of gases (carbon dioxide, water vapor, nitrous oxide, nitric oxide, ozone, volatile organic compounds) was determined in interstitial air withdrawn at eight heights in and above the snowpack at *hourly intervals. In this paper, carbon dioxide data from 2007 were used for evaluation of this technique. Ancillary data recorded inlcuded snow physical properties, i.e., temperature, pressure, and density. Various vertical concentration gradients were determined from the multiple height measurements, which allowed calculation of vertical gas fluxes through the snowpack using Fick's 1st law of diffusion. Comparison of flux results obtained from different height inlet combinations show that under most conditions fluxes derived from individual gradient intervals agree with the overall median of all data within a factor of 1.5. Winds were found to significantly influence gas concentration and gradients in the snowpack. Under the highest observed wind conditions, concentration gradients and calculated fluxes dropped to as low as 13% of non-wind conditions. Measured differential pressure amplitude exhibited a linear relationship with wind speed. This suggests that wind speed is a sound proxy for assessing advection transport in the snow. Neglecting the wind-pumping effect resulted in considerable underestimation of gas fluxes. An analysis of dependency of fluxes on wind speeds during a 3-week period in mid-winter determined that over this period actual gas fluxes were most likely 57% higher than Biogeochemistry (2009) 95:95-113 DOI 10.1007 fluxes calculated by the diffusion method, which omits the wind pumping dependency.

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Section: Co 2 Fluxesmentioning

confidence: 91%

“…Errors associated with the DM technique will be discussed with particular emphasis on the influence of wind-pumping. Results and discussion of measured gas fluxes and its ecological significance can be found in papers by Filippa et al (2009, …”

Section: Introductionmentioning

confidence: 99%

An automated system for continuous measurements of trace gas fluxes through snow: an evaluation of the gas diffusion method at a subalpine forest site, Niwot Ridge, Colorado

et al. 2009

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“…NO 2 ) flux. Seok et al (2009), Liptzin et al (2009), and Filippa et al (2008 evaluate how Fick's Law diffusion theory can be applied to derive trace gas fluxes of (NO ? NO 2 ), CO 2 , and N 2 O from the snowpack concentration gradients of these gases.…”

Section: Fluxes Of (No ? No 2 )mentioning

confidence: 99%

“…NO 2 ) fluxes from natural snowcovered landscapes, which previously have been neglected in assessing oxidized nitrogen cycling and/ or as an oxidized nitrogen source for atmospheric chemistry. Filippa et al (2008) provide a more in depth analysis of the soil nitrification and denitrification processes at NWT and the relative contribution of winter and summertime fluxes to the annual oxidized nitrogen exchange at this site.…”

Section: Fluxes Of (No ? No 2 )mentioning

confidence: 99%

Fluxes and chemistry of nitrogen oxides in the Niwot Ridge, Colorado, snowpack

et al. 2009

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The effect of snow cover on surfaceatmosphere exchanges of nitrogen oxides (nitrogen oxide (NO) ? nitrogen dioxide (NO 2 ); note, here 'NO 2 ' is used as surrogate for a series of oxidized nitrogen gases that were detected by the used monitor in this analysis mode) was investigated at the high elevation, subalpine (3,340 m asl) Soddie site, at Niwot Ridge, Colorado. Vertical (NO ? NO 2 ) concentration gradient measurements in interstitial air in the deep (up to *2.5 m) snowpack were conducted with an automated sampling and analysis system that allowed for continuous observations throughout the snow-covered season. These measurements revealed sustained, highly elevated (NO ? NO 2 ) mixing ratios inside the snow. Nitrogen oxide concentrations were highest at the bottom of the snowpack, reaching levels of up to 15 ppbv during mid-winter. Decreasing mixing ratios with increasing distance from the soilsnow interface were indicative of an upwards flux of NO from the soil through the snowpack, and out of the snow into the atmosphere, and imply that biogeochemical processes in the subnival soil are the predominant NO source. Nitrogen dioxide reached maximum levels of *3 ppbv in the upper layers of the snowpack, i.e., *20-40 cm below the surface. This behavior suggests that a significant fraction of NO is converted to NO 2 during its diffusive transport through the snowpack. Ozone showed the opposite behavior, with rapidly declining levels below the snow surface. The mirroring of vertical profiles of ozone and the NO 2 /(NO ? NO 2 ) ratio suggest that titration of ozone by NO in the snowpack contributes to the ozone reaction in the snow and to the ozone surface deposition flux. However, this surface efflux of (NO ? NO 2 ) can only account for a minor fraction of ozone deposition flux over snow that has been reported at other mid-latitude sites. Neither (NO ? NO 2 ) nor ozone levels in the interstitial air showed a clear dependence on incident solar irradiance, much in contrast to observations in polar snow. Comparisons with findings from polar snow studies reveal a much different (NO ? NO 2 ) and ozone snow chemistry in this alpine environment. Snowpack concentration gradients and diffusion theory were applied to estimate an average, wintertime (NO ? NO 2 ) flux of 0.005-0.008 nmol m -2 s -1 , which is of similar magnitude as reported (NO ? NO 2 ) fluxes

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“…In comparison, less focus has been paid to subalpine or alpine grasslands (Gilmanov et al, 2007;Soussana et al, 2007;Ammann et al, 2007), particularly during winter (Brooks et al, 1997;Gilmanov et al, 2004;Filippa et al, 2009;Liptzin et al, 2009;Merbold et al, 2012). For the full greenhouse gas balance of ecosystems, CH 4 and N 2 O have to be included, which may offset possible annual carbon sink capacities of terrestrial ecosystems (Nykanen et al, 1995;Zimov et al, 1996Zimov et al, , 1993Sommerfeld et al, 1996;Dise, 1992;Bubier et al, 2002;Chen et al, 2011a;Merbold et al, 2012;Oechel et al, 1997;Groffman et al, 2006;Schurmann et al, 2002;Yashiro et al, 2006;Filippa et al, 2009). Globally, rice paddies, wetlands and ruminant husbandry are the major CH 4 sources.…”

Section: Introductionmentioning

confidence: 99%

Winter greenhouse gas fluxes (CO2, CH4 and N2O) from a subalpine grassland

2013

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Abstract. Although greenhouse gas emissions during winter contribute significantly to annual balances, their quantification is still highly uncertain in snow-covered ecosystems. Here, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes were measured at a subalpine managed grassland in Switzerland using concentration gradients within the snowpack (CO2, CH4, N2O) and the eddy covariance method (CO2) during the winter 2010/2011. Our objectives were (1) to identify the temporal and spatial variation of greenhouse gases (GHGs) and their drivers, and (2) to estimate the GHG budget of the site during this specific season (1 December–31 March, 121 days). Mean winter fluxes (December–March) based on the gradient method were 0.77 ± 0.54 μmol m−2 s−1 for CO2 (1.19 ± 1.05 μmol m−2 s−1 measured by eddy covariance), −0.14 ± 0.09 nmol m−2 s−1 for CH4 and 0.23 ± 0.23 nmol m−2 s−1 for N2O, respectively. In comparison with the CO2 fluxes measured by eddy covariance, the gradient technique underestimated the effluxes by 50%. While CO2 and CH4 fluxes decreased with the progressing winter season, N2O fluxes did not follow a seasonal pattern. The major variables correlating with the fluxes of CO2 and CH4 were soil temperature and snow water equivalent, which is based on snow height and snow density. N2O fluxes were only explained poorly by any of the measured environmental variables. Spatial variability across the valley floor was smallest for CO2 and largest for N2O. During the winter season 2010/2011, greenhouse gas fluxes ranged between 550 ± 540 g CO2 m−2 estimated by the eddy covariance approach and 543 ± 247 g CO2 m−2, −0.4 ± 0.01 g CH4 m−2 and 0.11 ± 0.1 g N2O m−2 derived by the gradient technique. Total seasonal greenhouse gas emissions from the grassland were between 574 ± 276 and 581 ± 569 g CO2 eq. m−2, with N2O contributing 5% to the overall budget and CH4 reducing the budget by 0.1%. Cumulative budgets of CO2 were smaller than emissions reported for other subalpine meadows in the Swiss Alps and the Rocky Mountains. Further investigations on the GHG exchange of grasslands in winter are needed in order to (1) deepen our currently limited knowledge on the environmental drivers of each GHG, (2) to thoroughly constrain annual balances, and (3) to project possible changes in GHG flux magnitude with expected shorter and warmer winter periods.

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Winter and summer nitrous oxide and nitrogen oxides fluxes from a seasonally snow-covered subalpine meadow at Niwot Ridge, Colorado

Cited by 46 publications

References 57 publications

An automated system for continuous measurements of trace gas fluxes through snow: an evaluation of the gas diffusion method at a subalpine forest site, Niwot Ridge, Colorado

An automated system for continuous measurements of trace gas fluxes through snow: an evaluation of the gas diffusion method at a subalpine forest site, Niwot Ridge, Colorado

Fluxes and chemistry of nitrogen oxides in the Niwot Ridge, Colorado, snowpack

Winter greenhouse gas fluxes (CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O) from a subalpine grassland

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Winter and summer nitrous oxide and nitrogen oxides fluxes from a seasonally snow-covered subalpine meadow at Niwot Ridge, Colorado

Cited by 46 publications

References 57 publications

An automated system for continuous measurements of trace gas fluxes through snow: an evaluation of the gas diffusion method at a subalpine forest site, Niwot Ridge, Colorado

An automated system for continuous measurements of trace gas fluxes through snow: an evaluation of the gas diffusion method at a subalpine forest site, Niwot Ridge, Colorado

Fluxes and chemistry of nitrogen oxides in the Niwot Ridge, Colorado, snowpack

Winter greenhouse gas fluxes (CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O) from a subalpine grassland

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Winter greenhouse gas fluxes (CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O) from a subalpine grassland