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Visit the Maps Scheme maps:- |
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Taxonomy At the species level, Common Juniper, Juniperus communis L., is uncontroversial (Stace 1997). But it is a very variable species, and numerous forms have been described. These have a genetic basis, but whether they should be considered subspecies or merely varieties is debatable (Thomas, El-Bargathi & Polwart 2007). If you get two very different forms growing in one area, it may seem obvious which is which, but in other places there are intermediate forms that make it impossible to maintain such a clear distinction. At present, in Britain, three subspecies are accepted, but it is acceptable to simply record the species. The three subspecies are:-
Common Juniper is widely but unevenly distributed throughout the British Isles, mostly in grazed grasslands. Ssp. communis occurs throughout the range of the species, whereas ssp. nana is restricted to the west and the north. The ssp. hemisphaerica is recorded only in Pembrokeshire and Cornwall. It is one of the most common and widespread tree species in the northern hemisphere, occurring throughout much of Europe, North America and Asia, and even into North Africa. Ecology Juniper occupies many niches in vegetation communities: it can be the dominant canopy shrub in scrub, or it can be a small, ground-hugging plant in heaths or short grassland. Thomas, El-Bargathi & Polwart (op. cit.) describe it as occurring in calcareous, dry grasslands in the south of England and on wet, calcareous to acid soils in Scotland and the north. They list the following NVC communities for it: CG7, CG13, H7, H12, H14, H15, H20, W11, W13, W17, W18, W19 & W21.
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Status Juniper is listed as a priority species on the UK Biodiversity Action Plan (Anon. 1998) and is considered to be declining rapidly in Britain (Preston, Pearman & Dines, 2002). This is partly attributable to changes in land management (mainly loss of low-intensity grazed grasslands), but also apparently to poor reproductive capacity and competition with other plants, which is largely climate-related (Thomas, El-Bargathi & Polwart 2007). Due to its conservation status, Juniper is now often planted in the wild, particularly in southern England, and it was recorded as alien in 42 hectads in the New Atlas (Preston, Pearman & Dines, 2002). It may well have been planted in many of its 705 native hectads, as well. Future work It would be interesting to study the responses of Juniper to climate change and agricultural practices but, unfortunately, it is such a charismatic species that any natural changes are likely to be masked by conservation action - at least in England & Wales, where populations tend to be small. For the Maps Scheme, we do not distinguish between wild and planted populations, but anything that is planted in a garden or other obviously horticultural site should not be recorded at all. If it is planted in the wild, it should only be recorded if it persists for at least a few years. County recorders should try to maintain information on the extent of the introductions that occur. |
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Other information Juniper is unusual in having only immature foliage. Mature leaves in the Cupressaceae are scale-like and appressed to the stem. In most species the immature needle-like leaves soon fall off, but in juniper they persist indefinitely. References Anon. 1998. UK Biodiversity Group Tranche 2 Action Plans Vol. 1 – vertebrates and vascular plants. Publicity & Grants Team, English Nature, Peterborough. Preston, C.D., Pearman, D.A. & Dines, T.D. 2002. New Atlas of the British & Irish Flora. Oxford University Press, Oxford. Stace, C.A. 1997. New Flora of the British Isles, 2nd ed. Cambridge University Press, Cambridge. Thomas, P.A., El-Bargathi, M., & Polwart. 2007. Biological Flora of the British Isles: Juniperus communis L., Journal of Ecology 95, 1404-1440.
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Send us your comments and Feedback Sharon Pilkington (4/1/2008): In terms of NVC communities associated with Juniperus scrub on the chalk downlands of Wiltshire, it is almost invariably CG2 or CG3. I've also seen ssp. nana prostrate on limestone pavement in the Aran Islands, off Galway, and in the Burren, Co.Clare.
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