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In spite of the growing importance of the protective and social functions of forests, their productive function, including production of raw wood with a diversified assortment structure, is still prominent. Changes in the assortment structure depend to a large extent on tree species, habitat conditions and intensity of tending treatments. However, for the temporal organization of forest management, it is essential to recognize the dynamics of these changes in relation to stand age. The paper contains an analysis of quantitative and qualitative changes in the assortment structure of the Ist site index pine stands in the Wilcze Bagno Forest Compartment (Pisz Forest District), depending on the length of the primary production of standing timber. Data from 10 forest stands similar in terms of habitat, stand density and management treatments were taken for analysis. These stands form a homologous series ranging in age between 40 and 130 years.
The paper presents determination of the rotation age in Scots pine stands of 1st site index class on the example of Pisz Forest District (northern Poland). The development of quantitative and qualitative changes in the structure of 10 stands, forming a homologous series ranged between 40 and 130 years was the basis for determining their rotation age. Stand maturity for cutting was determined taking into account three variants of production targets considered alternatively. Traditional criteria and financial indicators were adopted to determine the rotation age. The traditional criteria included the absolute yield of a given variant, the average yield of an assortment per hectare and per year and the percentage share of each assortment group in relation to the growing stock of stands. The financial criteria included the assortment value of the considered variants of production targets, the average change in the value of these assortments, the percentage share of each assortment group in relation to the total growing stock and the average price of one cubic meter of the selected assortments groups.
Spontaneous regeneration in the hurricane−disturbed stand in the Pisz Forest District (N Poland) was registered in the years 2007−2008 and 2011−2012. Breast height diameter and crown size were measured on 10×10 m plots. The analysis also included the soil respiration rate, the decomposition rate of organic matter, soil pH, leaf area index (LAI), content of Mg, Ca, C, N and P in soil, and vegetation coverage of the forest floor. The natural regeneration was dominated by birch, followed by pine, which recolonized the disturbed stand in smaller extend, possibly because of the thick cover of organic material hindering germination and making it difficult for pine sprouts to reach the mineral soil. Spontaneous regeneration of the stand was most severely inhibited by Deschampsia flexuosa, whose growth over the entire surface was linked to the capture of excess released nitrogen resulting from the decomposition of organic matter. Mosses and lingonberry did not delay the spontaneous appearance of seedlings. The development of the natural regeneration suggests the possibility that an uneven−aged stand will emerge.
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