This study determined the correlation between the bulk density, humification degree and laboratory volume weight of the surface peat of virgin and drained peatlands. The material consists of 316 peat samples 250 cc in volume.
The correlation between bulk density and the laboratory volume weight was found to be close. Eliminating the ash and moisture content of air-dry samples did not improve the correlation. There were distinct level differences among peat types; difference between bulk density and laboratory volume weight was the greatest for Sphagnum and the smallest for woody peats. The Carex peats were intermediate. The water content at sampling may partly determine these differences. When the data were treated as a whole, the difference between bulk density and laboratory volume weight seemed to increase, as the water content increased.
The correlation was also close between bulk density and the degree of humification. For all data, multivariable correlation analysis revealed that bulk density was determined for the largest part by the degree of humification, least by the water content at sampling, laboratory volume weight being intermediate. Thus, already the determination of the degree of humification provides a clear picture of the bulk density for each peat type. It can be also determined by fair accuracy on the basis of the laboratory volume weight. The bulk density is required for e.g. water regime studies, to convert the water content of peat measured in weight units into volume percentages.
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