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The study describes allometric relationships between stand density and tree dimensions in birch stands on post−agricultural lands. The research material consisted of measurements carried out on 120 sample plots located in birch stands on post−agricultural lands of Central Poland. The investigated relationship was analyzed using ordinary least squares (OLS), dynamical formulation of allometric function (DFA), sto− chastic frontier production function (SFF) as well as quantile regression (QR) methods. Similar effects of modeling maximum density were obtained as a result of applying FFP and QR methods with 0.9 quan− tile. SFF was found to be the most adequate method for modeling maximum density.
Annillaria root rot, one of the most dangerous diseases in our forests, is caused in Poland mainly by Armillaria ostoyae, especially severe in young Scots pine stands, 'established after broadleaved stands or with participation of broadleaved species. in Forest District Zielonka young stands are severly affected by Armillaria root 'rot. Only one species, A. ostoyae, was found in the young (8-14 yrs) Scots pine stands, despite the presence of other Armillaria species in the district. The pathogen's frequent occurrence may be due, interalia, to favouring environmental, roots.
The aim of this study was to specify the above-ground biomass structure of black alder as well as to assess the influence of habitat conditions on biomass size and on allometric relation between biomass and breast height diameter. The empirical material consisted of 67 sample trees in age from 6 to 20 years selected from 17 stands growing on two types of forest habitat. The average share of stem wood in aboveground biomass of trees was 61.04%, branches 18.89%, bark and leaves 11.31% and 8.76% respectively. The fact that the examined stands constituted habitat type did not substantially influence either the biomass size or the relation between biomass and breast height diameter.
Paper discusses the influence of site quality on self−thinning process in silver birch stands growing on abandoned farmlands in Mazowieckie region (central Poland). Number of trees in a stand decreases with increasing age. The better the site (the higher site index value), the higher number of trees can be observed. However at the age of 10 difference between sites of various quality (site index) become insignificant. There is no need to include site index into the self−thinning models for young silver birch stands.
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