Carbon Distribution in a Hummocky Landscape from Saskatchewan, Canada

Abstract

Changes in the topography influence organic and inorganic C contents and δ13C values of soil C across a landscape. The objectives of this research were to: (i) study the effect of landscape on the formation and distribution of pedogenic carbonate and organic matter distribution in a hummocky landscape, and (ii) estimate the amount of organic C and pedogenic carbonate accumulation in local scale in comparison with regional scale using the stable isotope geochemistry techniques and standard characterization analyses. A hummocky landscape, typical of 38% of Saskatchewan's land, with glacial till parent material under virgin grassland, was studied. Organic C content of A horizons range between 20 to 98 g kg−1 Both extremes occurred in level positions of the south‐facing and north‐facing slopes. The lowest δ13C value of organic C (−29.6‰) was measured in a depression and the highest (more positive) was obtained on a shoulder (−21.7‰). The δ13C values of carbonate ranged from −0.9‰ (carbonated parent material) at the 114‐cm depth in level complex to −7.9‰ at depth of 100 cm in footslope complex and depression. The amount and percentage of pedogenic carbonate was higher in north‐facing slopes than in southward slopes. The highest proportion and amount of pedogenic carbonate up to 1‐m depth was found in Calcicryolls in footslope complex position in the north‐facing slope, and likely represents a gain in carbonate through lateral flows. The lowest proportion and amount (34.4% and 33.9 kg m−2) was found in the shoulder complex segment of west‐facing slope and in footslope complex position in east‐west direction. On average, the rate of accumulation is about 1.25 g C m−2 yr−1 of inorganic C (pedogenic carbonate) and 1.25 g C m−2 yr−1 as organic C. These are close to the calculated rate of 1.4 g C m−2 yr−1 for Dark Brown, and 1.3 g C m−2 yr−1 for Black soils (Mollisols) in Saskatchewan.

Permafrost soils and carbon cycling

“…Furthermore, as described above, patterned ground features can exhibit various combinations of these suborder soils, resulting in large local and landscape heterogeneity. A number of studies have looked at the SOC content of patterned ground features, for example frost boils (Dyke and Zoltai, 1980;Walker et al, 2004;Kaiser et al, 2005;Michaelson et al, 2012), circles (Kimble et al, 1993;Hallet and Prestrud, 1986), stripes (Walmsley and Lavkulich, 1975;Horwath et al, 2008), icewedge polygons Zubrzycki et al, 2013), and earth hummocks (Kimble et al, 1993;Landi et al, 2004). In addition to these pedon-scale studies, explicit efforts to account for and incorporate local-scale spatial heterogeneity into sampling designs and upscaling approaches are being explored for the estimation of SOC stocks on landscape or regional scales (Horwath et al, 2008;Hugelius and Kuhry, 2009;Zubrzycki et al, 2013).…”

Separation of grassland litter and ecosite influences on seasonal soil moisture and plant growth dynamics

“…Soil moisture is also strongly influenced across the landscape by topography, which may change spatial patterns of water runoff and deposition (Horton 1933;Meeuwig 1970;Bork et al 2001;Salve and Allen-Diaz 2001), as well as evaporation through surface exposure to solar radiation (Chapin et al 2002). Finally, landscape position influences soil texture and organic matter, further modifying water-holding capacity and infiltration, and changing hydrologic properties of the local ecosite (Landi et al 2004). Nonetheless, few if any of these factors can be readily manipulated to increase soil moisture through land management practices.…”

Capturing spatial variability of soil and litter properties in a forest stand by landform segmentation procedures

“…The principle that underpins landform segmentation is that many hydrological, and hence soil processes, are related to topographic attributes such as elevation, slope, aspect, and plan and profile curvature (Wysocki et al, 2000;Gallant and Wilson, 1996). Many studies have shown (Landi et al, 2004;Singh and Kar, 2001;King et al, 1999) that even subtle differences in topography can have a large effect on the spatial distribution of soil properties. Although these soil-geomorphic associations have conceptually been recognized for decades (Young and Hammer, 2000), landform segmentation enables rapid quantification and spatial analysis of the relationships, which can then be utilized for partitioning variability and ultimately predicting soil or other ecosystem properties.…”