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In Poland, the majority of silver fir stands is characterised by a single−layer stand structure. The current silvicultural activities aim at obtaining multilayer stands, which requires a clearer definition of the structure, and more precisely, a better knowledge of the pattern of diameters at breast height (DBH) distribution. The aim of the research was to develop a pattern of DBH distribution of trees in a multilayer silver fir stand in the Świętokrzyskie Mountains (central Poland) using the BDq method, through the mathematical determination of function parameters, including the productive capacity of the habitat. The application of this pattern will allow the selection of the management methods aimed to obtain and then maintain model stands with a different layer structure. The research was based on the empirical material collected in 56 stands that were characterized by both a single− and a multi−layered structure. They grew in coniferous forest habitats, mostly in the upland mixed coniferous forest, upland mixed deciduous forest and upland deciduous forest or mountain forest. One big (up to 1 ha) or 3−5 smaller (0.04 ha) sample plots were established in each stand in which diameters at breast height of all trees and heights of usually 25 trees, selected from the entire range of diameters, were measured. These were used to determine the height growth curve equation coefficients and then the height of each tree. For each stand the basal area was calculated and a graph for DBH distribution was prepared. Site index was established using the original empirical equation. In order to develop a model for multilayer fir stands, individual parameters of the equation 5, such as the basal area (B), the target diameter at breast height (D) and the coefficient q were to be determined using the BDq method. Taking into consideration only stands with one−tailed DBH, individual parameters of the function were found to be associated with site index. Empirical equations were developed for the determination of B and D, and, based on the DBH distribution graphs, coefficient q associated with site index was also calculated (tab.). The developed DBH distribution pattern is a mathematical description of the target fir stand. When the value of stand parameters approaches those of the model stand, it should be managed using the shelterwood cutting system, which results from the spatial variation in the stand height structure, and consequently from the need for different silvicultural treatments in different stand fragments.
This paper addresses problems associated with the silvicultural planning in the Norway spruce mire forests (Sphagno girgensohnii−Piceetum Polak. 1962) that are characterized by an uneven−aged structure and a high degree of irregularity at small scale. Based on detailed inventory using 30 permanent circular sample plots in two control units located in the Augustów Forest (NE Poland), the BDq method was employed for determining future silvicultural activities of the current forest management cycle. The equilibrium models are based on diameter distributions and have the following parameters, depending on site conditions: B=28 m2/ha; q−factor=1.32 and D=51 cm in the case of poorer forest site type (S.−P. typicum) and 55 cm more fertile one (S.−P. thelypteridetosum).
The paper deals with problems concerning silvicultural planning in silver fir stands in Zagnańsk Forest District (central Poland) that are characterized by complex structure. Based on a detailed inventory using 98 permanent circular sample plots in four control units the BDq method was employed for determining the future silvicultural activities of the current forest management cycle. The equilibrium model is based on diameter distributions and has the following parameters: B=35 m2/ha; D=63 cm and q−factor=1.28.
The paper presents preliminary results and experiences concerning promoting diverse structures in forest stands dominated by light demanding tree species, i.e. those that prevail under conditions of Polish lowlands. Data was collected in the ‘Control Unit Browsk 28C', established in 2002 in the managed part of the Biało− wieża Forest (eastern Poland) and surveyed again in 2011.
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