INFLUENCE OF PLANTINGS WITH OAK AND SPRUCE ON THE PHYSICAL-PROPERTIES OF SOD-PODZOLIC SOILS

The species composition of a planting has great influence on the physical properties of the soil. The soil in an oak forest is denser than in a spruce forest and contains more water-resistant aggregates primarily of large fractions. Water-resistant aggregates in an oak forest have denser packing. The upper plasticity limit (UPL) and shrinkage in water-resistant aggregates are higher than in the soil and its unaggregated part, which makes them isolated formations during swelling and shrinking. During swelling, the aggregates of small fractions occupy a significantly greater volume than large aggregates with their identical content as percentages by weight. This is also responsible for the fact that, with a small total content of water-resistant aggregates in the spruce forest, but with the predominance of small-fraction aggregates, the soil turned out to be more friable than in the oak forest.