『Abstract
　The soil emission rates (fluxes) of nitrous oxide (N2O) and nitrogen oxides (NO + NO2 = NOx) through a seasonal snowpack were determined by a flux gradient method from near-continuous 2-year measurements using an automated system for sampling interstitial air at various heights within the snowpack from a subalpine site at Niwot Ridge, Colorado. The winter seasonal-averaged N2O fluxes of 0.047-0.069 nmol m^-2 s^-1 were 〜15 times higher than observed NOx fluxes of 0.0030-0.0067 nmol m^-2 s^-1. During spring N2O emissions first peaked and then dropped sharply as the soil water content increased from the release of snowpack meltwater, while other gases, including NOx and CO2 did not show this behavior. To compare and contrast the winter fluxes with snow-free conditions, N2O fluxes were also measured at the same site in the summers of 2006 and 2007 using a closed soil chamber method. Summer N2O fluxes followed a decreasing trend during the dry-out period after snowmelt, interrupted by higher values related to precipitation events. These peaks were up to 2-3 times higher than the background summer levels. The integrated N2O-N loss over the summer period was calculated to be 1.1-2.4 kg N ha^-1, compared to 〜0.24-0.34 kg N ha^-1 for the winter season. These wintertime N2O fluxes from subniveal soil are generally higher than the few preciously published data. These results are of the same order of magnitude as data from more productive ecosystems such as fertilized grasslands and high-N-cycling forests, most likely because of a combination of the relatively well-developed soils and the fact that subnivean biogeochemical processes are promoted by the deep, insulating snowpack. Hence, microbially mediated oxidized nitrogen emissions occurring during the winter can be a significant part of the N-cycle in seasonally snow-covered subalpine ecosystems.

Keywords: Denitrification; Nitrification; Nitrogen oxides; Nitrous oxide; Snowpack; Soil biogeochemistry』

Introduction
Materials and methods
　Description of the study site
　Snowpack gradient sampling method
　　N2O data
　　NOx data
　N2O measurement method
　NO/NO2 measurement method
　Environmental parameters
　Winter flux measurements and calculations
　Summer flux measurements and calculations
　Soil analyses
　Statistical analyses
　Advection correction
Results and discussion
　Soil nitrogen pools
　Winter results
　Summer results
　Seasonal (NOx) and annual (N2O) budgets
　Comparison with other ecosystems
　Controls on N gas fluxes: summer period
　Controls on N gas fluxes: winter and snowmelt period
Conclusions
Acknowledgments
References