Assessment of TOC-SOM and SOM-TOC Conversion in Forest Soil

We analyzed relations between the content of total organic carbon (TOC) and the content of soil organic matter (SOM) in 47 soil profiles dug out in dry coniferous forests, fresh coniferous forests, and mixed deciduous-coniferous forests. Soils in the analyzed sites are derived from sands. In each soil horizon, bulk density (BD), pH, soil texture, and TOC and SOM were determined. Correlation between the content of TOC and SOM was significant in all layers (p<0.05), with correlation coefficients varying from 0.98 in the O horizon to 0.45 in the C horizon. The regression coefficient of linear equations for the SOM-to-TOC conversion decreased with soil depth. In the horizons occurring to a depth of ca. 20 cm (O, A, E), the regression coefficient for TOC as a predictor of SOM is 1.985, and for SOM as a predictor of TOC is 0.498, when R equals 0.989. In the B horizons, which form a layer to the depth of 30-50 cm, these coefficients amounted to 1.912 and 0.459, respectively. In the deeper layers, the relationship between TOC and SOM seems to be less evident. It was established that TOC determined is consistent with TOC calculated on the basis of the SOM-to-TOC conversion.