1. Siniša Andrašev, Instiute of Lowland Forestry and Environment, Serbia
2. Martin Bobinac, University of Belgrade-Faculty of Forestry, , Serbia
The paper presents the characteristics of the area potentially available on the basis of the Voronoi polygon before and after the thinning at the age of 11 years in the plantation of poplar clone I-214 established at a planting distance of 5 × 5 m, i.e., 400 trees per hectare. Researches were carried out on a permanent experimental plot in a random block design with two thinning treatments (the number of trees was reduced to 300 and 200 per hectare) and the control plot, in three repetitions. The area potentially available is defined by "Voronoi" polygon that covers the area nearest to each tree. In this way the defined polygons have their own characteristics (Hutchings and Discombe, 1986): (1) number of immediate neighbours, which is equivalent to the number of sides of polygon; (2) mean neighbour distance; (3) polygon perimeter length, (4) displacement - the distance of a point (tree) from the centre of gravity of the polygon it occupies; (5) area of the polygon.
It was found that before the thinning, the number of immediate neighbour trees was 4.26-4.51, as a result of the different survival of the seedlings, and it increased to 4.86-5.42 neighbouring trees. The average distance to the neighbouring trees was 5.26-5.65 m before thinning, and after thinning it increase to 5.9-7.4 m. The average size of the polygon area was 27.0-30.6 m2 before the thinning, and after the thinning it increased to 32.7-42.3 m2. Numerical indicators of the structure of the researched characteristics of the polygons have a pronounced positive asymmetry before the thinning, and the asymmetry is lessened after the performed thinning.
The results of the study indicate that the researched characteristics of the area potentially available, defined by Voronoi polygons, can be used as an objective representation of a competitive relationship between trees in poplar plantations.
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Датум:
08.09.2017.
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