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Znaczenie allelopatii dla hodowli lasu

86%
This paper addresses the question of whether or not and to which extent two common tree species mixtures (Norway spruce – European beech; sessile and pedunculate oak – European beech) vary in volume growth from their monocultures. To this end, the results from selected long−term experimental plots located in Germany, Poland and Switzerland, with many of them under survey since the 1890's, were employed. We found than on average both type of mixtures exceeded volume growth in pure stands by almost 30%. The analysis at the species level showed than only a Norway spruce response to mixture was neutral on average, while other tree species were benefitted by mixture. An empirical derived model for mixed stand of oak and European beech disclosed that the interaction can range from facilitation and overyielding on poor sites, through the neutral response under mesotrophic conditions, up to underyielding on fertile sites triggered by competition.
Airborne laser scanning (ALS) technology allows collecting data describing top forest layer in a very accurate way. This provides a possibility to generate crown height models (CHM) with resolution in which single tree crowns can be detected. In presented study highly automatic algorithm for single tree detection is presented. FALCON II ALS acquired data in Forest Experimental Station in Rogów (central Poland). Data used for algorithm accuracy evaluation were acquired by measuring sample plots on VSD photogrammetric station. CHM with the resolution of 0.5 m has been used in the presented research. Algorithm, in automatic or semi− −automatic way, defines single crowns. Each of the end segments was additionally processed for correctly defined size and area of the crown projection. Received accuracy of correctly detected trees was 69% for all samples (71% for pine stands and 61% mixed stands) in automatic method and 74% (78% and 65% respectively) in semi−automatic method.
Naturally regenerated silver birch is one of the most abundant competitor for planted seedlings in central Poland. The effect of the interaction between planted oak seedlings and naturally regenerated birch was studied in 14−17−years−old sessile oak stand. The experiment was established at stand age of 14−years. At that time, there were around 4000 oaks and 10000 birches per hectare. A sample of dominant individuals of oak were selected and one of three treatments were applied to each individual. The treatments included: (i) removal of all naturally regenerated trees in a radius of 1 m (W1), (ii) removal of all naturally regenerated trees in a radius of 2 m (W2) and (iii) untreated control (K). Breast height diameter and height of selected oaks were measured during three years following the experiment establishment. The release of competition resulted in greater diameter and height growth. The diameter growth was increasing with an increment of free space from oak and was the greatest in the W2 treatment. The increment of height growth was similar regardless of the treatment radius. In practical forestry, silver birch can be recommended as admixture in pure oak stands with low survival rate as replacement for dead oaks. However, a minimum distance of 2 m between oak and birch should be kept.
Growth and mortality of oak (Quercus robur L.) in young mixed stands with various admixture of hornbeam (Carpinus betulus L.) in the period of 9−13 years after planting were examined. The trial stand is located in central Poland (51.827023° N, 19.922315° E). It was established in 2004 on a moderately fertile site. Four experimental variants with different participation of oak (O) and hornbeam (H) were established: W1 – an oak monoculture (control variant, 100% O), W2 – a mixed stand consisting of two rows of oak and one row of hornbeam (67% O, 33% H), W3 – a mixed stand consisting of one row of oak and one row of hornbeam (50% O, 50% H), W4 – a mixed stand characterized by a single tree mixture, with three oaks and one hornbeam alternately occurring in each row (75% O, 25% H). During the first two years of the study period the height increments of oak trees were significantly larger in the study variants with hornbeam (the biggest in W3 variant), while during the next two years, the largest values of height increments occurred in the control variant (W1). Through the second part of the study period, the most pronounced, negative effect of hornbeam on the dbh increment of oak trees took place in the W3 variant. During the first nine years after planting the survival rate of oak trees in the variants with hornbeam were similar (82−94%) as in the control variant (85%). However, during the next four years, three times more oaks died in W3 variant (16,5%) than in other variants (5−7%). In general, the results obtained suggest that in order to create mixed oak stands with hornbeam as a nursery species, the share of hornbeam should not exceed 20−25% of all planted trees. The above value appears to be acceptable from the point of view of the negative competitive effects of hornbeam on oak trees during the initial stages of stand development.
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