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

The species composition of a planting has great influence on the physi cal properties of the soil. The soil in an oak forest is denser than i n a spruce forest and contains more water-resistant aggregates primari ly of large fractions. Water-resistant aggregates in an oak forest hav e denser packing. The upper plasticity limit (UPL) and shrinkage in wa ter-resistant aggregates are higher than in the soil and its unaggrega ted part, which makes them isolated formations during swelling and shr inking. During swelling, the aggregates of small fractions occupy a si gnificantly greater volume than large aggregates with their identical content as percentages by weight. This is also responsible for the fac t that, with a small total content of water-resistant aggregates in th e spruce forest, but with the predominance of small-fraction aggregate s, the soil turned out to be more friable than in the oak forest.