## 1 Introduction  
_Pinus cembra_ L., Pinaceae, Swiss stone pine, or arrola pine, is an alpine evergreen coniferous tree distributed in Europe in the Alps and the Carpathian Mountains. It grows in pure or mixed stands at high altitudes, 1500-2200 m, where it is well adapted to the alpine climate. Growing slowly, it can reach a height up to 25 m and an age of 1000 years [1]. However, due to natural competition and human activities such as alpine farming and timber extraction, the distribution of _P. cembra_ has been seriously compromised, which has led to a displacement to marginal habitats [2; 3; 4]. Regionally, _P. cembra_ has obtained economic significance. Commonly, the wood is used as building timber, for furniture production, and for artwork. Additionally, _P. cembra_ is grown in parks and gardens as an ornamental tree. Similar to other _Pinus_ species, _P. cembra_ is rich in aromatic volatile compounds and resins. These compounds are of interest for non-timber uses of the tree, and in some regions efforts are undertaken to promote this sector [5]. Essential oils represent the plant volatile fraction obtained by hydrodistillation or steam distillation; in the case of stone pine they are usually obtained from whole twigs with needles. In steam distillation, which is the widely used technique, a hot steam passing through the plant material extracts the volatile plant compounds. After condensation, the essential oils can be separated from the water phase [6]. Therefore, hydrolates or hydrosols are byproducts of the distillation, and contain low amounts of aromatic compounds soluble in water. Another increasingly applied technique uses supercritical CO\({}_{2}\) as an extractant to isolate the volatile fraction from plants. By adding modifiers, the selectivity of the extraction can be regulated [7]. However, these techniques are more sophisticated and need more intricate equipment than the classical distillation process, and are therefore costly. _P. cembra_ essential oils have various applications in medicine and aromatherapy, in local liquor production, and in the fragrance industry. Similarly, due to their aromatic properties, hydrolates are of interest for cosmetics. Stone pine products are sold to promote well-being. The aromatic compounds of the wood are said to have positive effects on indoor climate although this claim is not supported by scientific evidence. Several authors reported on the _P. cembra_ essential oil composition. \(\alpha\)-Pinene, limonene, \(\beta\)-phellandrene, and \(\beta\)-pinene in varying proportions were the main compounds [8; 9; 10; 11]. The plant material investigated for these reports came mainly from Eastern Europe or from botanical gardens. Volatiles emitted by _P. cembra_ cones of different geographic origins in the French Alps include \(\alpha\)-pinene (67-70%), \(\beta\)-pinene (18-20%), and limonene/\(\beta\)-phellandrene (8-11%) [12]. Only a recent study dealt with plants from a location in the Austrian Alps [13]. This study reports, in twig tips with needles, 44-48% \(\alpha\)-pinene, 13-17% \(\beta\)-phellandrene, 7-9% \(\beta\)-pinene, 4-6% limonene, and 5-7% germacrene D. As the evergreen tree produces large amounts of branches and greenery, this plant's raw material appears to be suitable for biosourcing interesting fractions or molecules. Products from other _Pinus_ species are of medical interest or, as in the case of turpentine oils, have industrial applications [14]. As the biological activities may change with the composition of the essential oil, a more detailed knowledge of the oil composition becomes necessary. As the variability of the volatiles in this species is not yet well documented and there are no reports on volatiles in _P. cembra_ hydrolates, the focus of the present research was:  
1. To investigate the variability in essential oil composition from three different collection sites;
2. To take sample from individual trees to get an insight in the chemical variation within populations;
3.