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ŠUMARSKI LIST 7-8/2022 str. 41     <-- 41 -->        PDF

Silver fir populations are a type of forest ecosystem that are autochotonous and originate from the glaciation period. The pattern of genetic differentiation fully corresponds to the morphological variation in the silver fir. Southern populations are much more variable (in some of the morphological traits like the number of stomates, needle thickness and width, etc.) compared to morphologically uniform northern populations (Paule et al. 2002).
The spatial variation of the silver fir morphological needle traits was observed in this study. Namely, the humidity index made the greatest impact on the obtained differences in the values of the morphological neeedle traits between populations. The values of the CMD water deficit index indicate the existence of drier environment in relation to other localities and depend on the degree of evaporation and precipitation on seasonal basis. Pirin and Osogovo populations had the lowest amount of precipitation compared to the others (about 600 mm/m2), whereas Pohorje as a population with lowest altitude (720 m a.s.l) had the amount of precipitation about 1251 mm/m2.
The morphological needle traits that are partly influenced by edaphic and climatic conditions were a useful tool in assessing the intrapopulation and interpopulation differentiation of Scots pine (Irvine et al. 1998, Niinemets et al. 2001, Pensa et al. 2004, Poljak et al. 2020, Ergül Bozkurtet al. 2021). They have also proven their importance in the characterization of the Pinus silvestris population and in the description of the geographical differentiation of this species (Urbaniak et al. 2003).
With increasing altitude environmental factors become more stressful, as a decrease of temperature and atmospheric pressure and an increase of precipitation and wind strength directly affect the growth and development of plants. The adaptive potential to environmental stress conditions is species-specific. The pattern of leaf morphology traits is determined by temperature and available water resources compared to spatial gradients (Zhu et al. 2022). Comparing the Fagus sylvatica morphological leaf traits and Picea abies morphological needle traits in a long period of time (two decades), it was found that the summer and autumn air temperatures in the previous year and reduced atmospheric pressure affected the Europeen beech leaf morphology, wherase spring air temperatures of the current year affected the Norway spruce needle morphology (Zhu et al. 2022). For example, the size of wild cherry leaves (as a broadleaves species) was influenced by the amount of precipitation in May and the De Martonne aridity index (Miljković et al. 2019). The number of days with temperatures below 0° C, the amount of precipitation and the altitude affected growth and phenology of Pseudotsuga menziesii (De La Torre et al. 2021). The interpopulation variability of P. tabuliformis morpho-anatomical needle traits also showed a positive correlation between the needle size and the amount of annual precipitation (Zhang et al. 2017), in contrast to P. yunnanensis needle size that showed a negative correlation with the amount of annual precipitation and temperature but a positive correlation with the latitude (Huang et al. 2016). In Pinus roxburghii, the needle length was shorter at higher altitudes (Tiwari et al. 2013). In our work, the the silver fir needle length was not correlated with altitude. Climate change increases aridity, and due to rising temperatures the rate of evapotranspiration increases, so that higher temperatures and less precipitation lead to climate stress caused by humidity. CMD as a quantification of stress caused by water deficit, which defines the dynamics of vegetation in ecosystems, is a parameter that is expected to increase in the future. In the Balkan Peninsula region, the projection is that these values will be three times higher than those recorded in the analyzed locations (Girvetz and Zganjar 2014). They will be close to the values recorded in the populations Pirin and Osogovo (CMD values 364 vs. 298; respectively), which have been confirmed to have influenced the silver fir morphological needle traits. The aridity index is in the semi-arid category (Nunes et al. 2016) in the areas where the populations Pirin and Osogovo are located (IDM values 32.13 vs. 35.99; respectively). Tara population is the central area of the silver fir distribution and belongs to the category of sub-humid area (IDM = 58.15). However, the microenvironmental conditions in the area indicate that the change in climatic factors occurred according to the projection of Girvetz and Zganjar (2014), i.e. to drier climate conditions.
The analyzed populations varied in the mean values of the silver fir morphological needle traits. None of the silver fir morphological needle traits was statistically significantly correlated with altitude, wherase the climatic factors were significantly correlated . Namely, the number of days with temperature < 0oC and > 18oC showed positive correlation, and the number of days with temperature > 5oC and > of 18oC showed negative with altitude. The Hargreaves climatic moisture deficit was the highest in the Pirin and Osogovo populations, as a consequence of the lowest values of mean annual precipitation in relation to the rest, although the impact on the silver fir morphological needle traits was not clear (the needle lenght was shorter in Pirin population compared to Osogovo, 2.47 cm vs. 2.75 cm; respectively). Research of the larger southern area of the silver fir distribution gives a better picture on the variability of the morphological needle traits in relation to the climatic characteristics that are both spatially and temporally divergent. The obtained pattern of variability in local