Carbon Balance in the Major Soil Zones of Saskatchewan
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Soil organic matter and carbonates are the two major e pools in the pedosphere, which are interconnected to the biosphere and atmosphere. The objectives of this study were to determine the present storage and accumulation rates of pedogenic carbonate and organic e using stable isotope geochemistry in a series of zonal (Brown through Gray) soils representing a gradient of time and environment in the Prairie Ecozone of Saskatchewan. The mass of organic e was 9.1 kg e m" for Brown, 11.7 kg e m-2 for Dark Brown, and 14.9 kg e m-2 for Black soils, decreasing to 9.6 kg e m-2 for Gray soils. A Rego Black Chemozem soil (carbonated phase) contained 21.0 kg C m'. The Ol3e values of organic e was -22.99100 for Dry Brown soils, -24.39100 for Brown soils, -24.89100 for Dark Brown soils, -25.39100 for Black soils, and -26.89100 for Gray soils. The storage of pedogenic carbonate increases from 133.9 kg m" in Brown soils to 164.5 kg m" in Gray soils, with corresponding rates of pedogenic carbonate accumulation of 8.3 to 14.3 g m-2 yr'. Values for the ol3e of pedogenic carbonates decrease from semiarid to humid soils, representing a decrease in the proportion of Ca plants in the vegetation. The depth of carbonate-free solum, the total pedogenic carbonate storage, and the rate of pedogenic carbonate accumulation all increase with increasing annual precipitation. In a landscape of Dark Brown and Black Chernozem soils on hummocky moraine, stores of e in soil organic matter and pedogenic carbonate were higher in soils on north-facing slopes than those on south-facing slopes. Soil organic C stores were larger in concave area in comparison to level areas with profiles> 1 m depth. Pedogenic carbonate stores to 1 m depth varied considerably over the landscape studied. Pedogenic carbonates were highest in rego soils on convex or planar slopes adjacent to leached depressions and in shoulder soils. Mean values of C accumulation in the form of pedogenic carbonate and soil organic C for the whole landscape were 14.1 and 15.0 kg C m", respectively. The results show that in addition to C sequestration in the form of organic C, substantial amounts of C are stored as pedogenic carbonate. Soils of grasslands and forests of the boreal regions have considerable potential to store C in organic forms in the short to medium term, and a long term potential as pedogenic carbonate.