Rocky Mountain juniper (Juniperus scopulorum Sarg.), an evergreen dioecious gymnosperm, is a widespread species in the western United States (Arizona, Colorado, Idaho, Montana, North Dakota, Nebraska, New Mexico, Nevada, Oklahoma, Oregon, South Dakota, Texas, Utah, Washington, and Wyoming) and is found in Canada and in Mexico (Adams, 2004; Scher, 2002; USDA, 2011). Despite the wide ecological adaption, Rocky Mountain juniper is not a primary source for lumber because of relatively slow growth. However, Rocky Mountain juniper wood is highly valued for its durability, rich color, pleasant aroma, antioxidant activity, and is extensively used for interior paneling, furniture, various novelties, and fence posts. The species has been used extensively in the ethnobotany of native people of North America to treat a number of medical conditions. Native people of North America have been using the leaves as medicine and the wood for preparation of bows, lances, flutes, and other important items (Hart, 1976; Kroeber, 1908). Rocky Mountain juniper is also an important species in the arid and semiarid regions of North America for a number of wildlife species such as deer, elk, small mammals, and birds, which use it for cover and a food source (Rumble and Gobeille, 2013; Scher, 2002). These animals play a major role in seed dispersal.
Rocky Mountain juniper leaves contain a significant amount of strongly aromatic essential oil, which has been subject to some previous studies (Adams and Hagerman, 1977; Adams and Powell, 1976; Cantrell et al., 2013; Zheljazkov et al., 2012a, 2012b). Previous investigations have found that sexual differences (Adams and Powell, 1976), seasonal changes (Powell and Adams, 1973), diurnal variations (Adams, 1979), and duration of distillation time (Zheljazkov et al., 2012a, 2012b) can affect Rocky Mountain juniper essential oil composition. However, there are no reports on variations of Rocky Mountain juniper essential oil year-round, from within a single tree, and on whether there are any seasonal differences between the composition of essential oil obtained from male and female trees grown side by side. Therefore, the objective of this study was to evaluate year-round variations in essential oil composition of Rocky Mountain juniper within one male and one female trees.
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