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ŠUMARSKI LIST 7-8/2022 str. 36     <-- 36 -->        PDF

(Postolache et al. 2013). The pattern of variability at the interpopulation and intrapopulation level has been modified by changing environmental conditions (Turunen et al. 1999; Klančniket al. 2014). Studies confirm that abiotic factors (edaphic and climatic conditions) significantly affect the morphological and anatomical traits of pine needles (Schoettle and Rochelle 2000; Jankowski et al. 2017), intrapopulation differentiation of morphological traits of Scots pine needles (Pinus silvestris), and geographical differentiation of species (Niinemets et al. 2001; Urbaniak et al. 2003; Pensa et al. 2004).
Degradation of silver fir (A. alba Mill.) is the result of lower interpopulation and intrapopulation (genetic) variability, which leads to decrease in the adaptive capacity compared to other forest species (Musil and Hamernik 2007). The abilities of plant species in forest ecosystems toadapt to climate change, and their distribution along a large scale of heterogeneous environmental conditions are determined by the genetic resources of species (Falk and Hempelmann 2013; Naudiyal et al. 2021). Climate changes modify the growth of forest ecosystem species, so that decades-old trees present an archival imprint of environmental change (Bradshawet al. 2000; Pandey 2021). Abiotic factors (altitude, air temperature, atmospheric pressure, photoperiod, precipitation, wind speed, mean annual temperatures), as well as nutrients, affect the physiological, anatomical and morphological traits of leaves or needles (Kašpar et al. 2017; Miljković et al. 2019; De La Torre et al. 2021). The morphology and anatomical structure of needles reflect their adaptation to changing environmental conditions (Xing et al. 2014). The most of needle traits are stable at the species level, but phenotypic variations in morpho-anatomical needle traits are the result of physiological adaptive evolution (Radu et al. 2014; Huang et al. 2016; Zhang et al. 2017; Wang et al. 2020). The characteristics of leaves / needles as the basic photosynthetic apparatus and the phenological phase of plants possess interspecific, interpopulation and intrapopulation differences due to changing environmental conditions (Turunen et al. 1999; Klančnik et al. 2014), as well as to age classes, and the position of leaves / needles in the canopy (Robakowski et al. 2004, Lukeš et al. 2013, Olascoaga et al. 2014). The morphological silver fir needle traits were used to determine the variability of natural populations in Northern Macedonia (Popnikola 1974), interindividual differentiation of trees in the western Serbia (Ratknić et al. 2013) and Tisovik Reserve (Pawlaczyk et al. 2005), and the influence of light on the seedling development (Robakowski et al. 2004; Dörken and Lepetit 2018).
The silver fir (A. alba Mill., Pinaceae) has the tallest tree in the genus Abies in Europe. In favorable environmental conditions it can live to the age of 500-600 years. Some mature trees can reach a height of 60-65 m and a diameter at breast height of 150-200 (380) cm. Natural habitats of silver fir are mountainous areas of Eastern, Western, Southern and Central Europe, where it grows mainly with beech (Fagus silvatica L.) at lower and middle altitudes and with spruce (Picea abies L. Karst) at higher altitudes (Liepelt et. al. 2009). The silver fir habitats spread from 52° N in the north (Poland) to 40° N in the south (northern border of Greece) and from 5° E in the west (western Alps) to 27° E in the east (Romania, Bulgaria). It occurs mainly at altitudes of 500 to 800 meters, and when going from north to south, the altitude increases. Due to the large distribution, this species is not yet endangered, although in the last 200 years silver fir forests have been significantly reduced in most European countries (Wolf 2003).
The aim of this research was to determine interpopulation and intrapopulation variability of the silver fir (A. alba Mill.) morphological needle traits and the contribution of certain climatic factors to its variability.
Plant material and needle traits
Plant material for morphometric analysis was collected in 16 natural, geographically distant, silver fir populations in the Balkan Peninsula during August 2019. Populations were located at altitudes ranging from 720 to 1860 meters above sea level. The following geographical and climatic characteristics were used in the analyses: altitude, latitude, longitude, MAT (mean annual temperature (°C)), degree-days: < 0, > 5, < 18, > 18 (days), CMD (Hargreaves climatic moisture deficit (mm)) and IDM (De Martonne aridity index) (Table 1). Hargreaves climatic moisture deficit is the climatic parameter calculated as the sum of the monthly (m) difference between a reference evaporation (Eref) and precipitation (P) (ClimateWNA, Wang et al. 2012). In the case Eref ≤ P (m), then CMD = 0, and if Eref (m) > P (m), then CMD = Eref (m) - P (m). Location aridity was estimated using the de Marton aridity index IDM = MAP / (MAT + 10). Mean annual temperature and precipitation were estimated for the period from 1961 to 2018 according to the ClimateEU v4.63 software package, available at (Hamann et al. 2013).
Each population was represented by 20 trees (approximately 80-100 years old). Branches with needles were sampled from the northeast side of the canopy at a height of about 6 meters. Analyzes were performed on 320 trees. A sample of 10 two-year old needles was randomly taken from the each branch (3200 needles in total).
The needle lenght (NL) was measured with a vernier caliper with an accuracy of 0.01 mm. The needle width (NW) and needle thickness (NT) were measured on microscope slides using a light microscope (Carl Zeiss Jena, Laboval 2),