The purpose of the work was to determine the changes in the gene pool (at the DNA level) of the pine stand, under the influence of various kinds of forest-tending cuts. The area in which the trials are carried out falls within the Warsaw Regional Directorate of the State Forests and its Forest District of Ostrów Mazowiecka, approximately 95 km towards the north-east of Warsaw.
Genetic structure was specified using five nSSR sequences and six cpSSR loci, while the five thinning variants trialled were: sanitation cutting, low thinning of 30% intensity, schematic thinning, selective thinning and destructive lumbering. The control variant was left untreated. It was virtual rather than real-life thinning that was pursued, using the ForestSimulator BWINPro program. Changes in the structure of the stand after a further 10 years were also simulated.
The different thinning variants were shown to cause change in the gene pool and level of genetic diversity of trees in the study area. In terms of maintaining genetic variability in the stand, the least-favourable method proved to be thinning from below–which resulted in the removal of 22% of nDNA rare alleles and 43% of cpDNA rare alleles. Destructive selection cutting was in turn most beneficial in terms of the preservation of genetic structure, with the reduction in rare alleles being more limited than in any other analysed variant. An increase in genetic diversity was also to be noted. It was with the selective thinning variant that the final number of trees, stand structure and level of genetic variation resembled the situation in the control most closely. This suggests that selective thinning provides for a rather accurate replication of processes occurring in nature.