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Athabasca County No. 12 AB

Primary productivity and decomposition in fens and marshes in the boreal region of Alberta

Author(s): Thormann, M. N.

Year: 1995

Net primary production (NPP), decomposition, changes in C, N and TP tissue concentrations and responses to N or P fertilization of aboveground vascular vegetation along a bog--fen--marsh peatland gradient in central Alberta, Canada, were measured during the 1993 and 1994 growing seasons. The peatlands were a bog, an open rich fen (ORF), a lacustrine sedge fen (LSF), a riverine sedge fen (RSF), a riverine marsh (RM) and a lacustrine marsh (LM). Total plant NPP of the bog and the fens were similar but significantly lower than that of the marshes. The plant production values obtained conform to a latitudinal gradient for North American wetlands, although the marshes of this study were substantially less productive than Canadian counterparts at similar latitudes. Moss and herb production varied significantly between years and among sites, whereas shrubs production only varied significantly among sites but not years. Litter quality and the surface water nutrient status of the sites partially explained the rates of decomposition of the dominant and standard plant litters and cellulose (filterpaper) over varying lengths of time. Decay of the plant litter was similar in fens and marshes, but cellulose decomposed significantly faster in the eutrophic marshes than in the oligotrophic fens. Nitrogen and phosphorus surface water parameters related best to litter decay in these peatlands. The carbon to nitrogen (C:N) ratio changes during plant litter decay depended on the litter type and quality and the surface water nutrient concentrations within sites. The nutrient status of the site, plant species, life history and stand density partly explained the C:N ratio changes throughout the growing season. Generally, C:N ratios decreased towards late August. Fertilization with N or P generally did not reveal which nutrient limits plant production in Alberta peatlands. In the bog, ericaceous and deciduous shrubs, mosses and herbs were variable in their responses to fertilization. Fen and marsh plant species generally did not respond significantly to N or P addition, possibly due to luxury consumption of the fertilizers or immediate microbial uptake.

The Athabasca fluting field, Alberta, Canada: Implications for the formation of large-scale fluting (erosional lineations)

Year: 2000

Current drumlin and fluting hypotheses, centred on processes of formation, erosion and deposition by subglacial deformation, accretion by lodgement, glacial erosion, and meltwater erosion and deposition, rarely receive comprehensive field testing. This paper documents the morphology, internal structure, and landscape associations of the Athabasca fluting field, Alberta, and discusses how well these characteristics are explained by postulated fluting forming processes. Fluting hypotheses are comprehensively tested by this approach and their rejection or acceptance are firmly based on field observation and knowledge of processes. Using multiple criteria, fluting is shown to be erosional and not to be a product of pervasive subglacial deformation or accretion by lodgement. Morphology, landscape associations, bed truncation, plus glaciofluvial lags and gravel on fluting ridges are inferred to support erosion by meltwater. Intact primary bedding, synsedimentary faults and injection structures very close to the landsurface, showing no sign of shear deformation, are used to reject erosion by subglacial deformation. Fluting is shown to be closely associated with tunnel channels and indicates that these channels were overtopped by broad floods that formed the fluting field and eroded anabranching tracts over the length of the Alberta Plains. Prior to fluting formation, sequences with melt-out and lodgement till, conduit sediment and boulder lags record net deposition over an extended time period. Diapirism prior to fluting formation marks a period of extreme pressure gradients which are related to bed separation. Following fluting formation, there was only minimal landscape modification, dominated by glaciofluvial and glaciolacustrine deposition, not glacial processes. This progression is presented as evidence for two very different glacial regimes separated by a short period with diapirism and extensive landscape modification by meltwater erosion. We note that the study area was glaciated only once, during the Late Wisconsinian, and it follows that glacial sedimentation and landscape modification were confirmed to this single glacial episode.