Pedological Investigations of Pleistocene Glacial Drift Surfaces in the Central Yukon

Distinct soil morphologies associated with three different ages of Quaternary glacial deposits are characterized and subsequently named. Properties which provide a basis for distinguishing these in the field include solum depth, B horizon colour, clay skin development, coarse fragment weathering and periglacial features. A strong relationship is evident between the clay content at depth and the age of soil. Low values of Na pyrophosphate-extractable Fe and Al confirm the absence of any active podzol-forming processes even within the reddest (5YR, 2.5YR) soil horizons. Wounded Moose paleosols are the preserved soils observed on pre-Reid Glaciation (.2-1.2 Ma) deposits which show strong paleoargillic horizon development with red colours, high clay content, and common periglacial modification. Diversion Creek paleosols are the preserved soils found on Reid (80-120 ka) glacial deposits which show moderate paleoargillic horizon development and resemble the contemporary Gray Luvisols of the mid and southern boreal forest regions of Canada. Stewart soils are the weakly developed Brunisols formed on stable landform surfaces of McConnell (14-30 ka) glacial deposits. The Wounded Moose and Diversion Creek paleosols, while found commonly in local areas, occupy only a small proportion of the regional landscape.On a dégagé les caractéristiques des sols (auxquels on a attribué des noms) dont les morphologies distinctes correspondent à trois épisodes de dépôts glaciaires du Quaternaire. Les propriétés pédologiques qui permettent de faire les distinctions sur le terrain sont la profondeur du solum, Ia couleur de l'horizon B, le développement des pellicules argileuses, l'altération des éléments grossiers et les caractéristiques périglaciaires. On constate qu'il existe une forte relation entre la teneur en argile en profondeur et l'âge du sol. Les bas taux de Fe et Al extractibles au pyrophosphate par le sodium démontrent l'absence de processus de formation de podzol, même dans les horizons les plus rouges (5YR, 2,5YR). Les paléosols de Wounded Moose sont les sols conservés que l'on peut observer sur les dépôts de la pré-glaciation de Reed (0,2-1,2 Ma) et qui montrent un fort développement de l'horizon enrichi d'argile à cause des couleurs rouges, de la haute teneur en argile et des modifications périglaciaires courantes. Les paléosols de Diversion Creek sont les sols conservés que l'on peut observer sur les dépôts de la glaciation de Reed (8000-12 000 ans) qui montrent un développement moyen de l'horizon enrichi d'argile et qui ressemblent aux luvisols actuels de Gray que l'on trouve dans le sud et le centre des forêts boréales du Canada. Les sols de Stewart sont des brunisols peu développés formés sur les reliefs stables mis en place par les dépôts de la glaciation de McConnell (14 000-30 000 ans). Les paléosols de Wounded Moose et de Diversion Creek, bien que courants à l'échelle locale, n'occupent qu'une faible partie du territoire.Unterschiedliche Bodenmorphologien werden auf drei verschiedene Episoden glazialer Ablagerungen im Quaternâr bezogen, cha-rakterisiert und anschlieBend benannt. Die Eigenschaften, welche eine Basis zur Unterscheidung dieser bei der Feldforschung liefern, sind die Tiefe des Solum, die Farbe des B-Horizonts, die Entwicklung der Lehm-Oberflàche, die Verwitterung grober Fragmente und die periglazialen Charakteristika. Es besteht offensichtlich eine enge Beziehung zwischen dem Lehm-Gehalt in der Tiefe und dem Alter des Erdreichs. Niedrige Werte von mittels Na Pyrophosphat herauslôsbarem Fe und Al bestàtigen das Fehlen jeglicher aktiver Podsol bildender Prozesse, selbst innerhalb der rôtesten Erd-Horizonte (5 YR, 2.5 YR). Die Paleosols von Wounded Moose sind die auf den Ablagerungen der Vor-Reid-Vereisung (.2-1.2 Ma) erhaltenen Bôden, welche eine starke Entwicklung des paleolehmigen Horizonts aufweisen, mit roten Farben, hohem Lehmgehalt und der ùblichen periglazialen Verànderung. Diversion Creek Paleobôden sind die auf glazialen Ablagerungen von Reid (80-120 ka) vorgefundenen erhaltenen Bôden, welche eine gemàBigte, paleolehmige Horizont-Entwicklung aufweisen und den gegenwàrtigen Luvisols von Gray âhneln, die man in der Mitte und im Sùden der nôrdlichen Waldgebiete von Kanada findet. Die Bôden von Stewart sind schwach entwickelte Brunisols, die sich auf den festen Oberflâchen-reliefs der glazialen Ablagerungen von McConnell (14-30 ka) gebildet haben. Die Paleobôden von Wounded Moose und Diversion Creek nehmen nur einen kleinen Teil der regionalen Landschaft ein, obwohl sie auf ôrtlichem Niveau allgemein zu finden sind

Observational constraints on the distribution, seasonality, and environmental predictors of North American boreal methane emissions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106685/1/GBC_20128_REVISED_suppinfo.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106685/2/gbc20128.pd

Massive Peatland Carbon Banks Vulnerable to Rising Temperatures

Peatlands contain one-third of the world’s soil carbon (C). If destabilized, decomposition of this vast C bank could accelerate climate warming; however, the likelihood of this outcome remains unknown. Here, we examine peatland C stability through five years of whole-ecosystem warming and two years of elevated atmospheric carbon dioxide concentrations (eCO2). Warming exponentially increased methane (CH4) emissions and enhanced CH4 production rates throughout the entire soil profile; although surface CH4 production rates remain much greater than those at depth. Additionally, older deeper C sources played a larger role in decomposition following prolonged warming. Most troubling, decreases in CO2:CH4 ratios in gas production, porewater concentrations, and emissions, indicate that the peatland is becoming more methanogenic with warming. We observed limited evidence of eCO2 effects. Our results suggest that ecosystem responses are largely driven by surface peat, but that the vast C bank at depth in peatlands is responsive to prolonged warming

Methane fluxes during the initiation of a large-scale water table manipulation experiment in the Alaskan Arctic tundra

Much of the 191.8 Pg C in the upper 1 m of Arctic soil of Arctic soil organic mater is, or is at risk of, being released to the atmosphere as CO2 and/or CH4. Global warming will further alter the rate of emission of these gases to the atmosphere. Here we quantify the effect of major environmental variables affected by global climate change on CH4 fluxes in the Alaskan Arctic. Soil temperature best predicts CH4 fluxes and explained 89% of the variability in CH4 emissions. Water table depth has a nonlinear impact on CH4 efflux. Increasing water table height above the surface retards CH4 efflux. Decreasing water table depth below the surface has a minor effect on CH4 release once an aerobic layer is formed at the surface. In contrast with several other studies, we found that CH4 emissions are not driven by net ecosystem exchange (NEE) and are not limited by labile carbon supply

Peatland Initiation, Carbon Accumulation, and 2 ka Depth in the James Bay Lowland and Adjacent Regions

Copyright © 2014 University of Colorado at Boulder, Institute of Arctic and Alpine ResearchPeatlands surrounding Hudson and James Bays form the second largest peatland complex in the world and contain major stores of soil carbon (C). This study utilized a transect of eight ombrotrophic peat cores from remote regions of central and northern Ontario to quantify the magnitude and rate of C accumulation since peatland initiation and for the past 2000 calendar years before present (2 ka). These new data were supplemented by 17 millennially resolved chronologies from a literature review covering the Boreal Shield, Hudson Plains, and Taiga Shield bordering Hudson and James Bays. Peatlands initiated in central and northern Ontario by 7.8 ka following deglaciation and isostatic emergence of northern areas to above sea level. Total C accumulated since inception averaged 109.7 ± (std. dev.) 36.2 kg C m–2. Approximately 40% of total soil C has accumulated since 2 ka at an average apparent rate of 20.2 ± 6.9 g C m–2 yr–1. The 2 ka depths correlate significantly and positively with modern gridded climate estimates for mean annual precipitation, mean annual air temperature, growing degree-days > 0 °C, and photosynthetically active radiation integrated over days > 0 °C. There are significantly shallower depths in permafrost peatlands. Vertical peat accumulation was likely constrained by temperature, growing season length, and photosynthetically active radiation over the last 2 ka in the Hudson Bay Lowlands and surrounding regions.US National Science Foundatio

Dissimilar responses of fungal and bacterial communities to soil transplantation simulating abrupt climate changes.

Both fungi and bacteria play essential roles in regulating soil carbon cycling. To predict future carbon stability, it is imperative to understand their responses to environmental changes, which is subject to large uncertainty. As current global warming is causing range shifts toward higher latitudes, we conducted three reciprocal soil transplantation experiments over large transects in 2005 to simulate abrupt climate changes. Six years after soil transplantation, fungal biomass of transplanted soils showed a general pattern of changes from donor sites to destination, which were more obvious in bare fallow soils than in maize cropped soils. Strikingly, fungal community compositions were clustered by sites, demonstrating that fungi of transplanted soils acclimatized to the destination environment. Several fungal taxa displayed sharp changes in relative abundance, including Podospora, Chaetomium, Mortierella and Phialemonium. In contrast, bacterial communities remained largely unchanged. Consistent with the important role of fungi in affecting soil carbon cycling, 8.1%-10.0% of fungal genes encoding carbon-decomposing enzymes were significantly (p < 0.01) increased as compared with those from bacteria (5.7%-8.4%). To explain these observations, we found that fungal occupancy across samples was mainly determined by annual average air temperature and rainfall, whereas bacterial occupancy was more closely related to soil conditions, which remained stable 6 years after soil transplantation. Together, these results demonstrate dissimilar response patterns and resource partitioning between fungi and bacteria, which may have considerable consequences for ecosystem-scale carbon cycling

An estimate of carbon emissions from 2004 wildfires across Alaskan Yukon River Basin

© 2007 Tan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Buried Peats: Past Peatland Distribution as an Indicator of Hydroclimate and Temperature

Peatlands, wetlands with > 30 cm of organic sediment, cover more than 3 x 106 km2 of the earth surface and have been accumulating carbon and sediments throughout the Holocene. The location of peatland formation and accumulation has been dynamic over time, as peat formation in areas like Alaska and the West Siberian Lowlands preceded peat formation in Fennoscandia and Eastern North America due to more favorable climate for peat formation. Using the geographic distribution of peatlands in the past can indicate general climatic conditions, including hydroclimate, given that the underlying geology is well understood. Peatlands form under a variety of climatic conditions and landscape positions but do not persist under arid conditions, instead requiring either humid conditions or cold temperatures. However, peatlands may have existed in the past in areas not currently suitable for peatland formation and persistence, but where peats can be found at depth within the sediment column. Here we map the locations of histic paleosols, relict peat, and buried peats since the Last Glacial Maximum using a compilation of sites from previous studies. We compare these records of past peatland distribution to present-day peatland distribution. We evaluate regional differences in timing of peatland development in these buried peatlands to the development of extant peatlands. Finally, we compare the timing of past peatland extent to the to modeled paleoclimate during the Quaternary. In addition to implications for paleoclimate, these past peatlands are not well accounted for in present-day soil carbon stocks but could be an important component of deep soil carbon pools