Assortment structure of harvested wood in age subclasses in selected cutting systems in Scots pine stands

Scots pine is the dominant forest tree species in Poland covering 58.0% of the forest area and constituting 61.1% of timber resources. Theoretically, all types of cuttings can be used in pine stands, but the purpose of the paper is to analyse the share of the main groups of assortments obtained from such stands with the use of: clear, group and gradual cuttings. It should be remembered that all types and forms of cutting are ideological, and the choice of a particular system should be determined by the silviculture goal. We used the data from the years 2012-2014 to conduct the research. The analysis covered Scots pine stands from all forest districts of the State Forests National Forest Holding, in which this species had a share of 80 to 100%. We analysed clear (I), group (III) and gradual (IV) cutting systems. Over 3.1 million hectares of mono-species pine stands was analysed. Numerical data was obtained from the database of the State Forests Information System. The studies took into account the assortments that actually occurred in a given subclass of age, divided into the type of cuttings, aggregated into three categories: small, medium and large-sized timber. In Poland, in mono-species Scots pine stands, mainly I and III cutting systems (about 97% of analysed stands) were used, the remaining types of treatments were sporadic. The largest share of harvest was characterized by the pulpwood assortment in harvesting I and III and the sawmill wood in the IV cutting system. With age, a decrease in the proportion of small-sized assortments and a gradual increase in the share of large-sized assortments was observed, while in the case of medium-sized assortments, the culmination of the share occurs at the age of 35-45 years, in all the analysed cutting systems. The course of the fraction of sub-classes in the case of large and medium-sized assortments in I and III cutting systems was similar.