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ŠUMARSKI LIST 7-8/2014 str. 19     <-- 19 -->        PDF

pedunculate oak forests are in the valleys of major rivers: Sava, Danube and Morava. It is characterized with very pronounced morphoanatomical, physiological and phenological variability (Batos, 2010). It has great economic importance in forestry, ecology, medicine, pharmacy and so on (Barbehenn et al., 2006; Rakić et al., 2007).
Pedunculate oak is an anemophilous and monoecius species. The flowers on the same tree are spatially separated. Male flowers (catkins) appear at the beginning of leafing in April or May, and are located in the grounds of this year’s or at the top of last year’s shoot. Female flowers occur somewhat later than male ones (7.5 days, according to Bacilieri et al., 1994), and are grouped at the top of this year’s shoot. In pedunculate oak the protandry is usual (Gomez-Casero et al., 2007), but there also may be found the protogyny (Franjić et al., 2011). Elongation phase of tassels occurs simultaneously with the differentiation of female flowers, while the receptivity of female flowers coincides with maturation time and dispersion of pollen. In the annual cycle of the pedunculate oak the flowering is usually in the spring, but there has been also registered a rare occurrence of summer flowering (Bobinac et al., 2000). On summer shoots pollen is very rarely formed, and it is significantly smaller in size than pollen from regular vernal flowering (Batos et al., 2012; Bobinac et al., 2012). The assumption is that the summer flowering can not be explained only by climate change, but as a primitive ancestral characteristic of Fagaceae family, where the oaks belong (Borzan, 2000).
Locations – Lokaliteti
The study was conducted in two populations of the pedunculate oak in two locations in the area of Belgrade (Serbia): "Ada Ciganlija" (AC) and "Bojčinska šuma" (BS). Populations are found in habitats that are suitable for the pedunculate oak, are of mixed structures, uneven-aged, coppice and seed origin, aged 60–120 years. Belgrade area is characterized with moderate-continental climate. The annual courses of temperature and precipitation are harmonized so that the months with the highest temperatures get the highest amount of rainfall which corresponds to the vegetation period.
Location "Ada Ciganlija" belongs to the city forest and is situated on the peninsula of the same name at the Sava riverside, in the habitat of ass. Fraxino angustifoliae – Quercetum roboris Jov. and Tom. 1979, on the soil type fluvisol calcaric. The construction of dams and other melioration works changed the habitat conditions (groundwater level), which caused a negative impact on the vegetation of the peninsula, especially on pedunculate oak. According to Lang’s climate classification features of the area (Unkašević et al., 2002), calculated value of the rain factor for this area for the current period (the last decade) is L = 55, which defines this area as ​​an area of steppes and savannas, and as a humid climate.
Location "Bojčinska šuma" is a suburban forest park which is a relic of the old swamp-lowland pedunculate oak forests that have been very widespread in this part of the river Sava coastal basin. It is the habitat of ass. Carpino – Quercetum roboris Rausch 1969. with soil type planosol dystric. The value of the rain factor in this area is L = 59, which defines it as a boundary between the steppe and savanna areas and low forests, and as a humid climate.
Climate data were obtained from the yearbook Report of the Republic Hydrometeorological Service of Serbia for the area of Belgrade.
Phenophase Fenofaza
Monitoring of the flowering phenophase was performed on a total of 58 (29 per site) trees of good growth and health, nearly of the same age. Observations were conducted once a week during spring (April, May) in three consecutive years (2004, 2005, 2006.). The first week of observation has been counted from the week in which has been noticed the earliest beginning of the flowering in the analyzed locations. Compared to the beginning of the phenophase there has been made a conditional grouping of trees on three phenological groups (Bacilieri et al. 1994): "early" trees that had a beginning of the phenophase in the first week of observation (the first week of April), "average" trees that had a beginning of the phenophase in the second week of observation (the second week of April), and "late" trees that had a beginning of the phenophase in the third week of observation or later (the third week of April or later).
Statistical analyses – Statistička obrada
For statistical analysis we used the number of days that represented the sum of days from the beginning of a calendar year until the date of registration of the observed process in the year of observation (Hemery et al., 2005). There have been used adequate procedures of the software package SAS 9.3 (SAS Institute, 2002) and the software package STATISTICA (Version 10). Beside the basic parameters of descriptive statistics to define the difference between the mean values of the flowering phenophase of populations within each of the observed years, we applied the Scheffe’s test. An estimation of the statistical significance of different levels of sources of phenotypic variation has been conducted using the analysis of variance (ANOVA). The locations have been treated as fixed factors (for clearly defined), while the tree has been treated as a random factor (because the election of trees within the location has been random).
Pedunculate oak begins to flower earliest on 7th April and no later than 2nd May in the analyzed locations, taking into account