Paleosols of the Interglacial Climates in Canada

Although paleosols are useful indicators of paleoclimates. it is first necessary to establish the relationships between the northern limits of the various contemporary soils and the pertinent climatic parameters. It is then necessary to determine the age of the various paleosols and, if possible, their northern limits. Comparison of the distribution and northern limits of the contemporary soils with the distribution and northern limits of the analogous paleosols then permits the reconstruction of the paleoenvironments. For the purposes of comparison the mean annual temperature of the Old Crow area during the Pliocene epoch was also determined (about 4°C) even though this was not an interglacial period. It was found that during the pre-lllinoian interglacial periods the central Yukon had a mean annual temperature of about 7°C while during the Sangamonian interglacial period it had a mean annual temperature of about - 3°C. During the Holocene epoch, the current interglacial period, the climate has been similar to or only slightly cooler than that existing during the Sangamonian interglacial period. The fluctuating position of the arctic tree line (and associated forest soils) during the Holocene epoch, however, indicates that the climate has also been fluctuating during this time. The paleoclimatic reconstruction presented in this paper also relies heavily on both diagnostic soil features and the soil development during the various interglacial periods.Pour que les paléosols soient des indicateurs utiles de paléoclimats, on doit d'abord établir les relations entre les limites nordiques des divers sols contemporains et les paramètres climatiques appropriés. On doit ensuite déterminer l'âge des divers paléosols et, si possible, leur limite nordique. La comparaison entre la répartition et la limite nordique des sols contemporains et celles des paléosols analoques permet alors d'effectuer une reconstitution des paléoenvironnements. Pour fins de comparaison ici, la température moyenne annuelle dans la région de Old Crow au cours du Pliocène a également été déterminée (environ 4°C), même s'il ne s'agissait pas d'une période interglaciaire. On a estimé que, durant les périodes interglaciaires pré-illinoiennes. Ie centre du Yukon avait une température moyenne annuelle d'environ 7°C. alors que durant l'interglaciaire du Sangamonien. Ia température était d'environ -3°C. Pendant l'Holocène, c'est-à-dire la période interglaciaire actuelle, le climat a été semblable ou très légèrement plus froid que pendant l'interglaciaire du Sangamonien. La fluctuation de la limite des arbres (et des sols forestiers associés) au cours de l'Holocène montre que le climat a également connu des changements. La reconstitution paléoclimatique présentée repose en outre sur des caractéristiques pédologiques diagnostiques et sur le développement du profil au cours des différentes périodes interglaciaires.Obwohl Palàobôden nutzliche Indikatoren der Palâoklimas sind, ist es nôtig. zuerst die Beziehungen zwischen den nôrdlichen Grenzen der verschiedenen gegenwartigen Bôden und den betreffenden klimatischen Parametern herzustellen. Dann muss das Alter der verschiedenen Palàobôden bestimmt werden und wenn môglich ihre nôrdlichen Grenzen. Der Vergleich der Verteilung und nôrdlichen Grenzen der gegenwartigen Bôden mit denjenigen der analogen Palàobôden erlaubt dann, die Palâoumwelten zu rekonstruieren. Zum Zweck des Vergleichs wurde auch die durchschnittliche Jahrestemperatur in der Gegend von Old Crow wàhrend des Pliozân bestimmt (ungefâhr 4 C), auch wenn dies keine interglaziale Période war. Man fand heraus. dass wàhrend der prà-illinoischen interglazialen Perioden im Zentrum von Yukon eine durchschnittliche Jahrestemperatur von ungefâhr 7°C herrschte, wohingegen es wàhrend des sangamonischen Interglazial eine Jahresdurchschnittstemperatur von ungefâhr - 30C gab. Wàhrend des Holozan, der gegenwartigen interglazialen Epoche, war das Klima àhnlich oder nur leicht kùhler als das, was wàhrend des sangamonischen Interglazial herrschte. Die Fluktuation der arktischen Baumgrenze (und der mit ihr in Verbindung gebrachten Waldbôden) wàhrend des Holozan weist indessen darauf hin. dass das Klima wàhrend dieser Zeit auch fluktuierte. Die in diesem Aufsatz vorgestellte palâoklimatische Rekonstruktion ruht auch in bedeutender Masse sowohl auf diagnostischen Boden-Merkmalen wie auf der Boden-Entwicklung wàhrend der verschiedenen interglazialen Perioden

Vulnerability of high latitude soil organic carbon in North America to disturbance

This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools into (1) near-surface soils where SOC is affected by seasonal freeze-thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not affected by short-term changes. We address key factors (permafrost, vegetation, hydrology, paleoenvironmental history) and processes (C input, storage, decomposition, and output) responsible for the formation of the large high-latitude SOC pool in North America and highlight how climate-related disturbances could alter this pool\u27s character and size. Press disturbances of relatively slow but persistent nature such as top-down thawing of permafrost, and changes in hydrology, microbiological communities, pedological processes, and vegetation types, as well as pulse disturbances of relatively rapid and local nature such as wildfires and thermokarst, could substantially impact SOC stocks. Ongoing climate warming in the North American high-latitude region could result in crossing environmental thresholds, thereby accelerating press disturbances and increasingly triggering pulse disturbances and eventually affecting the C source/sink net character of northern high-latitude soils. Finally, we assess postdisturbance feedbacks, models, and predictions for the northern high-latitude SOC pool, and discuss data and research gaps to be addressed by future research

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