Biological Flora of the British Isles: Juniperus communis L.

Abstract

Summary1. This account reviews information on all aspects of the biology of Juniperus communis that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. 2. Juniperus communis (juniper) is an evergreen dioecious gymnosperm shrub with two main population centres in Britain, one on chalk downlands of southern England and the other in northern England and Scotland. British populations are divided into two main subspecies although there is overlap in genetic and morphological features. Subspecies communis varies from a spreading shrub to an erect tree characteristic of calcareous soils in southern England, various soils in the Scottish highlands, while ssp. nana is a small procumbent shrub, restricted to well-drained bogs and, more usually, rocky outcrops, generally as a minor component of upland heaths and montane scrub. Both subspecies are drought and frost tolerant, although sensitive to fire. A third subspecies, hemisphaerica , primarily found in mountains of southern Europe has two small populations on maritime cliffs in the UK. 3. Although not very palatable, J. communis is grazed by small and large mammals when food is short, particularly in winter. Its low palatability is derived from oils found in the needles, cones and wood, dominated by monoterpenes. These have been extensively used in folklore medicine and to flavour alcoholic drinks, and are being investigated for new medicinal uses. 4. Juniperus communis ssp. communis is a characteristic light-demanding invader of pasture but has declined due to agricultural expansion, erosion, overgrazing, fire and poor regeneration, such that it is now rare and threatened across lowland/southern Europe. Although susceptible to overgrazing, some grazing can be beneficial to create the open sward necessary for seedling establishment. Other limits to regeneration are: progressively ageing stands in which male plants predominate; increasing fragmentation of stands that reduces pollination efficacy; and high seed dormancy with consequent variable germinability.Key-words : climatic limitation, communities, conservation, ecophysiology, geographical and altitudinal distribution, germination, herbivory, mycorrhiza, parasites and diseases, reproductive biology, soilsJournal of Ecology (2007) 95 , 1404-1440 doi: 10.1111/j.1365-2745.2007.01308.x *Abbreviated references are used for many standard works: see Journal of Ecology (1975), 63 , 335 -344. Nomenclature of vascular plants follows Flora Europaea and, where different, Stace (1997). †Author to whom correspondence should be addressed: P. A. Thomas. E-mail: p.a.thomas@biol.keele.ac.uk. Pinopsida (Coniferae), Cupressaceae. The junipers are a taxonomically difficult group, composed of about 68-80 s...

Grassland Fires in Hungary – Experiences of Nature Conservationists on the Effects of Fire on Biodiversity

“…The reason for this is that Juniperus ignites easily, and its high content of volatile oils makes it highly susceptible to burning. In most cases fire extirpates shrubs locally (ANPD, BNPD, KNPD; Ónodi et al, 2008, Thomas et al, 2007). Fire is also an important natural determinant of the dynamic of ecosystems dominated by J. communis.…”

Quality of Juniper Essential Oil (Oleum Juniperi) in the South Slovakia and it’s Curative and Industrial Utilization

“…Today, juniper population is found in a wide range of open habitats, at varying altitudes and growing in a wide range of soil types (Cooper et al) It favors free-draining soils, rocky outcrops and rarely inhabits wet conditions (Thomas et al, 2007). The species has a low tolerance to shade (Grubb et al, 1996) and is gradually excluded from woodland.…”

Juniperus navicularis - a study of Portuguese population structure and fitness

“…Junipers produce a large proportion of apparentlyviablebutemptyseeds (Thomas& al., 2007), but proportions of viable seeds obtained in this study are lower than those found for J. communis in Iberian Peninsula (García & al., 2000) or for the endangered J. oxycedrus ssp.macrocarpa (Juan&al.,2003(Juan&al., , 2006andverylowwhencomparedtosimilar studies with other junipers (Rumeu & al., 2009) (García & al., 2000;Wesche&al.,2005;Otto&al.,2012).…”

“…Along with irregular seed production, most junipers have germination limitations duetoageofthejuniperbush,insectpredation and empty seeds (Thomas & al., 2007;Verheyen&al.,2009),andalsotodormancy directlyassociatedwiththeembryo,theseed coat impermeability or the presence of germinationinhibitors (Juan&al.,2006).These recruitmentlimitationsmightalsobeexacerbatedbyclimatealterations,sincemorefrequentwarmeranddriersummerscaninfluence seed production and viability due to water deficit stress (García & al., 1999;García & al., 2000;Muñoz-Reinoso, 2003). According to IUCN Red List of Species, from the 1052 gymnosperm known species, 399areconsideredthreatened(38%),anumber that more than doubled in the last 17 years (IUCN, 2014).…”