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ŠUMARSKI LIST 3-4/2019 str. 68     <-- 68 -->        PDF

the Kentucky coffeetree natural range is wide, it is nowhere abundant and it can be found at the edges of woods and along streams (Werthner et al., 1935). It is typically distributed as widely separated single trees or small groups that are presumably clonal and is the result of root suckering (McClain and Jackson, 1980). On natural sites of Kentucky coffeetree, there are no special means of dispersal of the fruit, so the natural distribution of the fruit is scanty. Even a strong wind cannot carry the pods far and it is not known that the rodents are storing them for food (Werthner et al., 1935). It is hypothesized that the Kentucky coffeetree is an ecological anachronism, sinking to extinction in the wild because nothing animate appears to be its primary or secondary dispersal agent in natural and semi-natural habitats in North America (Zaya and Howe, 2009). The leaves and the fruit are poisonous (Pammel, 1911), so the species is generally resistant to herbivory (Janzen, 1976). Thanks to the Native American ethno-botanical practices, the current range of the species is, to a certain extent, shaped by human influence which is suggested by the strong correlation between current stands of Kentucky coffeetree and former Native American settlements (VanNatta, 2009). The problem of poor natural regeneration of this dioecious species is even more difficult having in mind that there are populations with sexual structure that consists only of single-sex individuals (Environment Canada, 2014).
In the territory of Serbia, the species G. dioicus has been present for over 150 years, and it was most commonly cultivated in the form of decorative single trees or small groups of trees in the parks and estates of former noblemen in Vojvodina and one site was registered in Topčider in the territory of Belgrade (Petrović, 1951; Bobinac et al., 2017). The largest, heterogeneous group of trees is at Fruška Gora on the site of pedunculate oak and hornbeam. The data about the growth elements of this group of trees (culture) are presented at the age of 17 years (Petrović, 1951) and at the age of 75 years (Bobinac and Stojadinović, 2007; Bobinac et al., 2008). According to these authors, Kentucki coffeetree has potentially high productive possibilities and can be considered as a fast growing tree species which makes it economically interesting on this site. The justification of cultivation of the species is confirmed by anatomical research which pointed out that G. dioicus has good wood properties, and is especially recommended for recultivation of degraded sites (Vilotić et al., 2011; Jokanović et al., 2015). The research and observations in the cultures in Serbia have pointed out the limited ability of subspontaneous expansion of G. dioicus as well as some biological traits that could be useful in the control of subspontaneous expansion in the cultures (Bobinac et al., 2017; Bobinac et al., 2018).
The aim of this paper is to point out the growth elements of trees and the stand of G. dioicus at Fruška Gora (Serbia) and consider their values depending on different growing space in the culture.
Research object – Objekt istraživanja
The culture of G. dioicus is situated in the western part of National park ’’Fruška Gora’’ (in the territory of forest administration Erdevik, φ=45°07’N, λ=19°21’E), in a wide stream valley 120 m above sea level. The culture was raised on a pedunculate oak-hornbeam site (Carpino betuli-Quercetum roboris /Anić 59/ Rauš 1971.) (Tomić, 2013).
Regarding the geographical position, this area is under the influence of humid continental climate. Based on the data from the weather station Sremska Mitrovica (φ=45°06’N, λ=19°33’ E, elevation=82 m above sea level), the mean annual air temperature is 11.3 °C. The absolute maximal temperature of 43.6 °C was measured in July and the absolute minimal temperature of –29.5 °C was measured in January. The mean annual rainfall is 614.2 mm with 60% falling during the growing season (data from the Republic Hydrometeorological Service of Serbia for the closest weather station for the period 1981–2010).
The culture is established in the spring of 1932 with seedlings 2.5 m tall, with 3 × 3 m spacing (1111 trees per hectare) in a triangular pattern. The seedlings were produced in Ilok (Croatia) in the nursery of the landowner Odeskalski who owned the culture at the time. At the end of 1948 (17 years after the establishment) 70 trees were measured (833 trees per hectare) with a quadratic mean diameter (dg) of 12.4 cm, Lorey’s mean height (hL) 10.5 m, basal area 10.11 m2·ha-1 and estimated volume of 68.30 m3·ha-1 (Petrović, 1951).
The establishment of G. dioicus culture at Fruška Gora is the result of individual collectoral activity, directed to the expansion of the floristic diversity of the area with the main purpose of using it as hunting grounds for big game.
Because of its botanical peculiarity for the territory of Serbia, the culture was put under special protection in the National park in 1978 in the category Natural monument (1981). Later, the change in attitude towards allochthonous species that took place in the National park caused the cancelation of the protection (2004) and the culture was left to spontaneous development as it was the case before protection.
The researched G. dioicus culture is in the surrounding of other tree species of similar age and is partially formed in the irregular geometric shape. The crowns of the trees on the edge of the stand were under the influence of approximately double the growing space compared to the space between the rows in the stand (3 m).
In order to define the total area covered by the stand, and the growing space of the trees in it, every tree was set in the local coordinate system of the stand. In this local coordinate system, the border of the experimental plot was defined by