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ŠUMARSKI LIST 3-4/2019 str. 74     <-- 74 -->        PDF

Discussion and conclusions
Rasprava i zaključci
The species Gymnocladus dioicus (L.) K. Koch has been present in the territory of Serbia for over 150 years and it is one of the earliest introduced species (Bobinac et al., 2017). Usually, the tree was used decoratively, in the form of single trees or in small groups in parks and estates of the former nobleman in Vojvodina. The species regenerates well from seed and root suckers, but it doesn’t show invasiveness (Bobinac et al., 2017). That is the reason why the species is mostly present only in locations where it was introduced until the first half of the 20th century having in mind that in the later period, only single trees and small groups were planted. In the current reviews of exotic species in Serbia (Perović and Cvjetićanin, 2005) G. dioicus is not identified as the species that is important for a broader use in silviculture.
The largest and the best preserved heterogeneous group (culture) of trees of G. dioicus in Serbia is at Fruška Gora on the site of pedunculate oak and hornbeam. In the researched culture at Fruška Gora, the growth elements of the trees of G. dioicus (in the first place, the dominant height of 35 m and Lorey’s mean height of 33 m) at the age of 85 years from the establishment are pointing out the productive potential of the pedunculate oak site for the silviculutural cultivation of G. dioicus. According to Halaj et al. (1987) and Jović et al. (1989-90), pedunculate oak reaches above mentioned heights on best sites. In the researched stand, the highest recorded height of G. dioicus tree at the age of 85 years was 37 m.
The growth elements are pointing out the high productivity of the culture in the observed ages. At the age of 85 years from the establishment, 502 trees per hectare were registered with quadratic mean diameter (dg) of 39.6 cm, dominant diameter (D100) 51.5 cm, Lorey’s mean height (hL) 33.0 m, dominant height (H100) 35.0 m, basal area 61.74 m2·ha-1 and volume 918.23 m3·ha-1. The current volume increment was 18.80 m3·ha-1 in the age period 76-80 years and 18.27 m3·ha-1 in the age period 81-85 years (Table 1).
The variability of height distribution of the trees in the stand is significantly smaller compared to the variability of the diameter distribution and that is the characteristic of stands consist of trees with the same age (Andrašev, 2008). The conducted analysis showed that the structural characteristics and the growth elements of the stand are defined by the growing space of the trees so the two different collectives of trees were separated in the stand.
The collective of inner trees (A) is falling behind in diameter and height growth, compared to the collective of edge trees (B), that is shown by the achieved mean and dominant diameters and heights (Table 5), as well as the significant differences between the current diameter, height, basal area and volume increments (Table 8). In the collective A, in the observed 10-year period, the processes of a strong differentiation between the trees occurred. That is presented by higher values of coefficients of variation of diameter and height distribution compared to the collective B (Tables 6 and 7). That resulted in the reduction of the number of trees, due to mortality, wind breakage and windthrow compared to the initial state at the age of 75 years.
The above shown relations in the structure and the value of increment of different collectives of trees in the stand are pointing out the strong reaction of edge trees, i.e. the trees that grew in more favourable conditions at the same age. This implies the need for application of tending measures in order to maintain the optimal levels of increment. The trees in the stand are characterized by straight stem, well cleaned from branches. The slenderness index, as an indicator of the stem form (Pretzsch, 2009), is 93 in the collective A and 21% higher compared to the collective of edge trees (B) where it amounts 77. Besides the high productivity of dendromass, the mentioned indicators are pointing out that this species can be directed to the production of technical assortments of good quality. The species has quality wood, but is prone to rough branching (Petrović, 1951) so it would be important to investigate the optimal value of the growing space for the trees in the process of establishing cultures and