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ŠUMARSKI LIST 5-6/2019 str. 28     <-- 28 -->        PDF

different native oak species and discussed primarily from the silvicultural aspect: in pedunculate oak (Bobinac 1994; Bobinac 2011; Bobinac and Karadžić 1994; Pap et al. 2013); Turkey oak (Bobinac 1997; 2001; Bobinac and Vilotić 1998); Hungarian oak (Šušić 2017) and sessile oak (Krstić et al. 2018).
According to Harmer (1990; 1992), the shoot elongation in Q. robur and Q. petraea occurs in a rhytmic pattern of rapid shoot extension altering with periods of inactivity when the terminal bud is developing. In woody plants, multi-flush growth is better expressed in juvenile trees compared to adult trees (Borchert 1976). There is a strong relation between the annual shoot elongation of the plants and the number of height-growth flushes in the growing season (Phares 1971; Collet et al. 1997). Due to the young crops ability to adapt to environmental conditions, multi-flush growth enables it to maintain the aimed height faster, so the regeneration period can be shortened in the conditions of high control of the natural regeneration process in pedunculate oak forests (Bobinac, 1999; 2011). However, multiple flushing may cause the occurrence of different deleterious stem forms in young plants of many woody species (Cline and Harrington 2007). The higher susceptibility to the powdery mildew (Erysiphe alphitoides Griff. et Maubl.) of pedunculate oak leaves from later growth flushes in the growing season and the dieback of flushes is related to the multi-flush growth as well (Bobinac 2011; Pap et al. 2012).
The results of many studies suggest that the light conditions are an important factor that affects the height growth of different oak species in the first growing season and it was noted that the growth is differentiated under different light conditions (Bobinac 1997; 2011; Bobinac and Ballian 2010; Cardillo and Bernal 2006; Jarvis, 1964; Kolb et al. 1990; Ovington and MacRae 1960; Phares, 1971; Ponton et al. 2002; Roth et al. 2011; van Hees, 1997; Ziegenhagen and Kausch 1995).
There is little information about the growth characteristics of Hungarian oak in the initial stage of development in Serbia, particularly regarding the multi-flush growth as a characteristic trait of genus Quercus L. Having this in mind, the aim of this paper was to investigate the growth characteristics of one-year-old Hungarian oak seedlings in full light conditions and contribute to a better understanding of the ecology of the species.
Research object – Objekat istraživanja
In the nursery of Faculty of Forestry in Belgrade (coordinates: 440 78’25,23’’N, 200 42’55,19’’ E), a field experiment was set in the autumn of 2015 at 125 m a.s.l. on the area of 10 x 1.5 m. The acorn sowing was carried out in approximately 5 x 15 cm spacing. The acorn was collected a few days before sowing in a stand of Hungarian and Turkey oak close to Kraljevo (coordinates: 430 68’45.16’’N, 200 54’62.99’’ E).
According to Nonić (2016), the soil in the nursery is characterized by low to moderate alkaline pH value (7.64–8.43), sufficient provision of N, P and K and favorable mechanical composition. The research area is characterized by the zonal forest vegetation at the southern boundary of Pannonia, Quercetum cerridis-virgilianae (Jov. et. Vuk. 77) that is in direct contact with the zonal forest vegetation of Hungarian and Turkey oak (Tomić 1991).
In 2016, the mean annual and the mean air temperature of the growing season was 1.3°C higher compared to the 1981–2010 average (12.5°C). As for precipitation, the annual amount as well as the amount of precipitation in the growing season of 2016 were higher by 74.1 mm (10.7%) and 30.1 mm (7.7%) respectively compared to the 1981–2010 average (690.9 mm). The data were collected from the website of Republic Hidrometerological Service of Serbia***.
Sampling and the analysis of the plant material –Uzorkovanje i analiza biljnog materijala
At the end of the growing season 2016, 400 normally developed plants were randomly sampled from the area of the field experiment and used for morphometric analysis. Plants were measured by non-destructive analysis. The measured morphological parameters were the total height of seedlings (Ht) and the height of growth flushes (H1–n) using the ruler with the accuracy of 0.5 cm and the root collar diameter (Drc) measured just above the cotyledon scars using the Vernier caliper with the accuracy of 0.1 mm. For the identification of the cotyledon scars, the soil was previously prepared. The growth flushes (shoot phases) determination was based on the number of scars of juvenile buds on the annual axis, in the way described by Bobinac (1994; 2001), i.e. the occurrence of proleptic shoots was determined in the way described by Gruber (1992) (Figure 1).
The total number of leaves (LN) was determined for every phase of growth (growth flush). Three leaves were collected per growth flush and herbarized separately. The leaves were scanned and their leaf area was measured in ImageJ software (Schneider et al. 2012). The leaf area was used for the calculation of the average leaf area in the growth flush. The determination of the total leaf area of every growth flush was done in the following way: the mean value of the measured leaf area, based on three collected leaves was multiplied with the total number of leaves of the flush. The determination of the total leaf area for the whole seedling (TLA) was done by adding the values of leaf areas of all the growth flushes belonging to the specific seedling.