The aim of this research was to study the effect of the stand composition on the density of pine and spruce wood growing on former arable lands. Sample areas are located in mixed mature pine- and spruce-prevailing stands in Leningrad region, Russia. For the reliable determination of the basic density of spruce and pine wood, selection of model trees was carried out and cores were taken. Based on the data obtained from stems of 36 model trees from 3 sample plots, conversion equations were calculated to determine the basic density of wood. The measurements of the spruce and pine wood density were processed using variational statistics. The results have shown that the pine forms a more homogeneous wood than the spruce. On former arable lands, spruce has a denser wood than pine under the same growth conditions. The stand composition has a significant effect on the density of spruce rather than pine.

The purpose of the study was to compare forest and postagrogenic soils by parameters such as carbon content in organic matter and total nitrogen to predict the fertility state of lands that are at the stage of restoration of woody vegetation. Areas with similar soil formation conditions were selected on the postagrogenic and forested lands having mature forest stands related with such types of forest: Myrtillosum forest, Oxalidosum and Herbosa-Composita forest, and also areas under the soil complexes of postagrogenic fallow lands. A number of physico-chemical indicators for the soil were assessed according to the methods generally accepted in soil science: the particle size distribution, the bulk density and the thickness of the pedogenic horizons were determined. An analysis of the carbon stocks in organic matter (Corg) and nitrogen (Ntotal) in the genetic horizons of the soils of myrtillosum, Oxalidosum and Herbosa-Composita forest types shows an increase in the content of organic matter and total nitrogen from Myrtillosum to Herbosa-Composita forest type. A comparative analysis of the physical and agrochemical state of postagrogenic and forest soils showed that, despite the previous anthropogenic impact, the agroland horizon retains a high content of organic matter and total nitrogen. The properties of postagrogenic soils in the studied areas are not deteriorated, and the transformation towards the natural forest soils of the region is not observed, despite the long period of fallowing.