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Natural populations of Rubus hirtus Waldst. & Kit. were studied at three locations along the Gabrovnica river on Stara Planina mountain, to assess the inter-population differences in ecophysiological and ecomorphological parameters. The content of total chlorophyll in leaves, estimated by the SPAD method, as well as leaf width and leaf width/length ratio had the highest values in population A, which inhabits a forest community dominated by hornbeam and sessile oak and grows in vegetative shade. Populations B (which is also located within the forest complex) and C (which is located in a relatively open habitat) had lower values for the examined parameters. Inter-population differences in the examined parameters can be partially interpreted as an adaptation to habitat light conditions (significant differences between individuals from populations A and C). However, the values of parameters in population B cannot be explained by light conditions, indicating the need to consider complex environmental conditions at that site, primarily heavy metal contamination of soil and groundwater.

In studies of population variability, particular attention has to be paid to the selection of a representative sample. The aim of this study was to assess the size of the new representative sample on the basis of the variability of chemical content of the initial sample on the example of a whitebark pine population. Statistical analysis included the content of 19 characteristics (terpene hydrocarbons and their derivates) of the initial sample of 10 elements (trees). It was determined that the new sample should contain 20 trees so that the mean value calculated from it represents a basic set with a probability higher than 95 %. Determination of the lower limit of the representative sample size that guarantees a satisfactory reliability of generalization proved to be very important in order to achieve cost efficiency of the research. [Projekat Ministarstva nauke Republike Srbije, br. OI-173011, br. TR-37002 i br. III-43007]