Lacelle et al. 2010

Lacelle D, Radtke K, Clark ID, Fisher D, Lauriol B, Utting N, Whyte LG. 2011. Geomicrobiology and occluded O2-CO2-Ar gas analyses provide evidence of microbial respiration in ancient terrestrial ground ice. Earth and Planetary Science Letters 306: 46-54.

These authors compared the gas composition of ice from massive ground ice bodies (e.g. 30 000-year-old buried snowbanks) to atmospheric gas concentrations and gas contents from glacial ice. They also cultivated some microorganisms collected from within the ice, and used some non-culture-dependent methods to examine the diversity of those organisms.

Loss of O2, as determined by comparison of the ratio of O2 to Ar in samples, as well as changes to the 13C-CO2 contents indicate heterotrophic microbial activity in the ice, most likely by organisms living in high-salt brine channels in cracks in the ice, using dissolved organic carbon as both energy and C source.

This paper provides an overview of methods for extracting and measuring the gases trapped in microscopic bubbles in permafrost and ground ice, as well as interesting findings about microbial activities.

Lacelle et al. 2008

Lacelle D, Juneau V, Pellerin A, Lauriol B, Clark ID. 2008. Weathering regime and geochemical conditions in a polar desert environment, Haughton impact structure region, Devon Island, Canada. Canadian Journal of Earth Science 45: 1139-1157.

These authors examined the soils and waters near the Haughton crater on Devon Island, to determine the importance of chemical and mechanical weathering in this polar desert environment. They examined dissolved material in streams, lakes, snow, and groundwaters, and the size distribution, shape, and chemical composition of particles from soils in several different local landforms and parent materials.

Despite low temperatures, low precipitation, and very low vegetation presence, significant chemical weathering was found. Signs of chemical weathering, rather than mechanical, include rounded surfaces and pits in sand particles and the concentrations of Ca2+, Mg2+, and HCO3- in waters. Signs of mechanical weathering were also found, including sharp fracture lines in particles.

A gradient of increasing chemical weathering and decreasing mechanical weathering was found from the surface to the permafrost table. Thermal buffering reduces the frequency of frost-driven forces and thermal expansion from daily at the surface to annually at the permafrost table. The permafrost acts as a barrier to water movement, creating relatively wet condtions at depth that allow aqueous chemistry including the dissolution of dolomite to proceed.

Xu et al. 2009

Xu C, Guo L, Ping C-L, White DM. 2009. Chemical and isotopic characterization of size-fractionated organic matter from cryoturbated tundra soils, northern Alaska. Journal of Geophysical research 114, G03002.

These authors examined the isotopic composition and organic matter distribution in soil horizons and particle size fractions from two soils in Alaska, a moist acidic tundra and a moist non-acidic tundra. The organic matter quality and quantity in the deeper part of the active layer and down into the permafrost, material estimated to be between 3000 and 7000 years old indicated high susceptibility to microbial activity, that is, decomposition to CO2 and subsequent release to the atmosphere.

I read this paper as part of my background reading to understand the potential uses of a Picarro field-portable carbon isotope analyser; this paper includes a description of the δ13C values of organic matter throughout the soil / permafrost profiles of these Alaskan soils. These values, and the associated discussion of signatures of microbial activity, suggest it is quite possible to distinguish the source of CO2, permafrost-SOM, deep-SOM, shallow/autotrophic, based on the 13C content of effluxing CO2 and / or CO2 at various depths within a soil profile. Table 5 is particularly valuable in this regard.

Lin et al., 2009

Lin X, Wang S, Ma X, Xu G, Luo C, Li Y, Jiang G, Xie Z. 2009. Fluxes of CO₂, CH₄, and N₂O in an alpine meadow affected by yak excreta on the Qinghai-Tibetan plateau during summer grazing periods. Soil Biology and Biochemistry 41: 718-725.

I read this paper in an attempt to gain a better understanding of the methods used to compare greenhouse gas fluxes between ecosystems or treatments, and between gases, particularly the use of CO₂-equivalents when estimating total global warming potential contributions by ecosystems that may be simultaneously sources and sinks for the greenhouse gases CO₂, CH₄, and N₂O. In addition, this is one of a small number of studies I have been able to find that draw conclusions about global warming potentials based only on growing season measurements, rather than whole-year or growing season plus “cold season” (often what the tourist industry might call the shoulder seasons, spring and fall, though sometimes including winter as well).
These authors studied the effects of yak (Bos grunniens) excreta, dung and urine, on soil emissions of the three greenhouse gases. Excreta were hypothesized to increase GHG emissions because both are rich in nitrogen, especially inorganic forms of nitrogen such as urea, ammonia, and nitrate, contain sufficient water to stimulate microbial activity in dry soils, and, in the case of dung, are rich sources of labile organic carbon compounds and large microbial populations already present in the material. Furthermore, because production of CH₄ by grazing mammals is strongly linked to their digestive systems, fresh dung may contain considerable dissolved CH₄ that will be emitted quickly upon excretion.
The main results of this study were that while fresh dung did significantly shift a patch of meadow from a weak sink for CH₄ to a source, this difference was not sufficient to render the larger meadow area a net source because the spatial distribution of dung patches, as well as the duration of the CH₄ emission from dung, were relatively small. Urine application did not significantly increase CH₄ emission, which is surprising considering the high N concentration and rapid, large addition of water represented by urination by a yak; both factors are expected to increase methanogenesis.
Emissions of CO₂ were increased by dung, but not by urine when considering a longer, cumulative set of emissions. Interestingly, urine produced a significant pulse of CO₂ nearly immediately upon application to the soil, though whether this CO₂ is the result of hydrolysis of urea ((NH₂)₂CO + H₂O --- 2NH₃ + CO₂) or increased microbial respiration is not clear.
Emissions of N₂O were increased by both dung and urine application relative to untreated controls. However, the magnitude of the increase was less than predicted by IPCC (2001) guidelines for calculating the effects of grazing mammals on grasslands; those guidelines were based primarily on temperate low-altitude grasslands, not the high-altitude alpine meadows studied here. In general, patches of yak excreta accounted for an increase in N₂O emissions of up to about 10% compared to ungrazed and untreated control meadow, while total CO₂-equivalents emissions increased by about 1%, largely due to the small total areal extent of excreta patches.