Organic carbon stocks in swedish podzol soils in relation to soil hydrology and other site characteristics

Abstract

Site characteristics influence soil organic carbon (SOC) stocks. In Podzols under Swedish forest land, SOC stocks were related to latitude, altitude, soil hydrological class categorized by mean groundwater level, mean annual precipitation, temperature sum during the growing season, total annual nitrogen (N) deposition and site capacity. SOC stocks were determined for the O-horizon and for total soil (O-horizon + mineral soil to a depth of 50 cm). Data from the Swedish National Forest Soil Inventory 1993-2001 were used (1477 field plots). The O-horizon was sampled with a core sampler and carbon (C) stocks were determined. For the mineral soil layers the SOC stock was calculated based on the SOC concentrations, bulk density and content of rock fragments. The results showed that the overall mean SOC stock was 2.8 and 8.2 kg C m-2 for O-horizon and total soil, respectively. Soil hydrological class strongly affected SOC stocks, which increased from on average 6.7 kg C m-2 at dry sites to 9.7 kg C m-2 at slightly moist sites. Corresponding values for the O-horizon were 2.0 to 4.4 kg C m-2. The correlation coefficients for the linear relationship between SOC stock and site characteristics were highest for N deposition, which explained up to 25% of variation, and latitude, which explained up to 20% of variation. Altitude had the lowest degree of explanation.