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Juniperus communis L.
Common Juniper, Bastard’s bane, Dwarf Juniper, Meryw, Aiteann, Iubhar Creige
CUPRESSACEAE SYN.: none
Status: Serious decline over the last 25 years UK BAP Priority species since 1999 805 10 km squares 1987-1999 Lead partner: Plantlife International Schedule 8 Wildlife and Countryside Act
UK Biodiversity Action Plan (BAP) These are the current BAP Targets following the 2001 review: T1 - Maintain the current range of Juniper. T2 - Maintain the overall population size of Juniper. T3 - Achieve natural regeneration of Juniper populations at sites under direct conservation management. T4 - Maintain, or re-establish, populations at sites not under direct conservation management. T5 - Restore representative tree-line Juniper populations. Progress on targets can be viewed by clicking on: http://www.ukbap.org.uk. The full Action Plan for Juniperus communis can be viewed by clicking on: http://www.ukbap.org.uk. PLEASE NOTE: In this dossier, the main emphasis is on Juniperus communis ssp. communis, although there are sections that include information about the other sub-species, their taxonomy and distribution. Generally, a reference to Juniper or Juniperus communis means the whole species, and references to sub-species are made explicit.
Contents 3 Ecology & Life Cycle......................................................................................23 4 Habitat Requirements ...................................................................................32
4.1 Communities & Vegetation .......................................................................32 4.2 Summary of Habitat Requirements ............................................................35
5 Management Implications ..............................................................................35 6 Threats / Factors Leading To Loss or Decline or Limiting Recovery .......................38 7 Current Conservation Measures ......................................................................40
7.1 In situ Measures .....................................................................................40 7.2 Ex situ Measures.....................................................................................41 7.3 Research Data ........................................................................................41 7.4 Monitoring Juniper & the Common Monitoring Standard ................................42
8 References ..................................................................................................42 9 Acknowledgements .......................................................................................45 10 Contacts...................................................................................................45 11 Links........................................................................................................46
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3 Ecology & Life Cycle This section is written with particular reference to Juniperus communis ssp. communis. Juniperus communis ssp. communis reproduces mainly by sexual means in drier areas and at lower altitudes. However, in the Lake District and Scotland, where the ground is boggy and individuals are of more prostrate varieties, it can be exceedingly difficult to distinguish individuals (Smith, 1980) and it is likely that there are large clones. Experiments in Canada on rooting cuttings of J. communis ssp. depressa have also shown that ability to root is greater in northern populations and in females (Houlé & Babeux, 1994). Vegetative reproduction is commoner in old declining stands (Falinksi, 1980). Layering does sometimes occur even on the drier chalk grasslands in the south of England. Larger, aging bushes collapse, the branches touch the ground, and occasionally re-root, as shown by a much more vigorous and greener branch. However, in these dry situations the re-growth does not always persist after the centre of the bush has died. Juniper is wind-pollinated. The male flowers open in spring and there are pollen sacs attached to each of the cone scales (see Figure 12). Clouds of pollen can sometimes be seen in windy conditions. Pollen sticks to the receptive droplets on the female flowers (see Figure 13) and as the pollen tube elongates the berries begin to develop. In the first year the berries (strictly speaking cones or galbuli) are green but they progressively ripen and turn purple after fertilization at the beginning of the second year – mostly around August to November (see Figure 14).
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Figure 12 – Male cones of Juniperus communis in spring with cone scales and pollensacs. Left – pollen sacs full; right – pollen sacs discharged. (Photographs by Lena Ward).
Figure 15 – Sections of 1st year (green) and 2nd year (purple) Juniper berries in autumn. (Photograph by Lena Ward).
Figure 14 – 1st year Juniper berries (green) and 2nd year berries (purple) in autumn. (Photograph by Lena Ward).
Figure 13 – Receptive droplets on female cone flowers of Juniper in spring. (Photograph by Lena Ward).
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The berries of Juniperus communis contain from one to five seeds, usually three (see Figure 15). However, many seeds that appear intact on the outside may not be so inside, e.g. at Porton Down only 3.7% of 417 seeds sampled from 40-year old bushes in October 1998 were normal. This abortion appears to relate to predation, failure of pollination and the nutritional status of the bush. It also varies geographically, empty seeds being much commoner in the south of the range (García et al, 2000). Older bushes have fewer good seed than younger bushes (Dearnley & Duckett, 1999; Ward, 1981; Diotte & Yves, 1989). In the UK seeds are killed by several species of insects / mites e.g. Juniper Seed Chalcid (Megastigmus kuntzei), Juniper Shield Bug (Elasmostethus tristriatus), Juniper Berry Miner (Argyresthia praecocella). The Juniper Berry Mite (Trisetacus quadrisetus) inflicts the most serious damage, and has been recorded affecting 82% of berries. The seed bank type of Juniperus communis is classified as transient (Thompson et al, 1997) meaning that the seeds persist in the soil for less than one year. This fits reasonably well with incidental information, as very occasionally young Juniper does reappear on recently extinct sites. Most records of Juniper appearing spontaneously are apparently from bird dispersal. Seed germination of Juniperus is complex and not convenient for artificial manipulation for sowing (Pack, 1921). The seeds from berries ripening in the autumn require a long period of after-ripening, and as few as 1% germinate without an after-ripening period. The embryo shows root and shoot dormancy (Sebastian, 1958) and the seeds require two winters before they germinate in spring (in April - May in southern England). Germination has been reported to vary greatly according to the specific treatment and seed source (Johnsen & Alexander, 1974). This variability is considered to be an ecological adaptation that increases the chances for a species to establish in unpredictable habitats and those that result from catastrophic events (Broome, in press). A suggested procedure is two periods of cold stratification at 90 days for 3.5oC separated by 60-90 days at 20oc diurnally. This resulted in successful germination of 70-75% of the seeds over 20-30 days. Broome (in press) recommends that seeds are removed from the fruit and soaked in 1% citric acid solution for 4 days before being stored in well-aerated conditions at 4oC for 30 weeks to break their dormancy. If seed is left out of doors in compost and kept free of rodents, a few will germinate in the first year, most in the second year, and several more over the next two-three years. In germination experiments at Lochaber, seedlings continued to emerge for 5 years with a peak in germination at 2 years and 7 months (Broome, in press). Ripe berries are dispersed by birds in the autumn, and there is extensive literature on this subject, especially for Spain (Garcia, 2001; Garcia et al, 2001). Bird dispersers mainly belong to the Turdidae (Thrush family) and large flocks of fieldfares are particularly important in spreading Juniper to new sites. Some berries are attacked by insect pests, and are then less attractive to birds (García et al, 1999), so favouring the dispersal of undamaged cones. Some berries fall to the ground beneath the bushes. Others persist uneaten on the tree, often turning brown; such berries usually containing fewer fertile seeds. Berries on the ground and those accessible on the bushes are also eaten by rodents such as voles and wood mice (King & Wilson, 2001). Rosen (1988) reports that domestic sheep may also serve as a dispersal agent since Juniper is often associated with sheep droves. Young seedlings of Juniper are slow growing and are most often found in un-grazed situations in communities with much bare ground or little competition from other vigorous plants -usually due to low nutrient conditions (Vedel, 1961). There are usually vigorously fruiting, but not old, parent bushes within a few hundred metres of young seedlings. Regeneration with many age classes on one site is unusual in southern England unless there is continual erosion of the ground or intermittent periods of grazing (Ward, 1981). A good example of natural regeneration on eroding steep roadside banks showed how pioneer Juniper on these new sites had produced numerous seedlings
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locally (Banks, 2001). It will be interesting to see how well these seedlings survive. Mice and voles eat both young seedlings and seeds (Barrett, 1997). Most of the younger stands of Juniper in the south regenerated after rabbits were lost by myxomatosis in 1954-5 (e.g. Porton Down). Regeneration continued for a narrow time span of about 11 years and then apparently ceased because of competition from other plants. Rabbits returned in the mid 1970s and caused serious damage (see Figures 16 & 17). Young seedlings are vulnerable to summer drought (Garcia et al, 1999; Rosen, 1988 & 1995), and we may speculate that this climatic factor might have implications for Juniper with any future global warming. Conversely, where seedlings are grown in very moist conditions as in plant nurseries, they may succumb to Phytothphora, Phomopsis and other fungi. This may happen in some conditions in the wild. Young Juniper plants are very vulnerable to damage, especially when they are shorter than the height of a grazing rabbit. They have less protective bark and may be more easily killed outright by ring barking. Very young seedlings do sprout again from the base but not so vigorously as Crataegus (Hawthorn), and a few persist for years as grazed plants a few centimetres tall. If grazing is relaxed these shoot up. However, where there is frequent serious grazing damage, Juniper is progressively killed and regeneration will be very poor (Morris et al, 1993; Gilbert, 1980). The greater number of sheep grazing in the Lake District together with an absence of Juniper regeneration is thought to be a cause of the imbalance of age classes, with the grazed older stands having poorer reproductive capacity (Dearnley & Duckett, 1999). In northern areas, particularly in Scotland, both deer and sheep browsing damage Juniper. Sullivan (2003) showed that pioneer plants suffered heavy browsing early on, although prostrate plants are heavily browsed throughout their life cycle, probably because of their accessibility. Miller & Cummins (1998) found that the Juniper was browsed in winter when other foliage was scarce. However, snow-lie does protect prostrate Juniper from browsing (Sullivan, 2003). Broome (in press) suggested that shelters 0.60 m in height should be used to protect Juniper from grazing as these improve plant growth. Although they have an effect on growth form, shelters should be removed at about five years. After removal, there was no evidence of collapse. Juniper is shade intolerant at all stages of life, particularly at the young seedling stage. Although seedlings may initially be protected from grazing and browsing under older bushes, the older plants and seedlings may then die under the shade of successional yew trees (Watt, 1926) (see Figure 18). Juniper can survive under light shade, and in some cases the Junipers are drawn up and become very tall. For example, Humphrey (1996) showed successful establishment and growth in 20.5% daylight levels typical of 40 year old, thinned Scots pine woodland. In Scotland, Juniper may be an understorey in birch woodland e.g. Morrone Birkwood NNR. Sullivan (2003) showed that shading of woodland Juniper caused it to die (2% of surveyed woodland populations affected) and may be responsible elsewhere when deaths were unexplained, in 42% of surveyed woodland populations. Snow break in woodland populations was another important factor in branch death (Sullivan, 2003). Broome (in press) suggested that weed control was beneficial to the establishment and growth of Juniper. The mean annual increment of growth of Juniper growing on Porton Down, measured for one hundred bushes, 40 years old, was 7cm, but individual growth varied according to the year, health and sex of the bushes from 1cm to as much as 28cm. This particular stand reached maturity after about 9 years for males and a little later for females (Ward, 1981). Other observations suggest that this time can be shorter for plants growing on better soils, while being much later for Juniper in alpine/northern conditions. In Scotland, the growth rate for Juniperus communis ssp. communis is typically 3-5 cm per year (Broome, in press). The varieties of Juniper tend to grow at different rates, some are exceedingly slow growing, especially Juniperus communis ssp. nana, while some of the tallest Juniper
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2002
1977
1973
1969
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Figure 16 – History of a Juniper population at Porton Down (note the same Yewtree on the downland in the background): 1969 – Population regeneration afterrabbits died from myxomatosis in 1955; 1973 – growth continuing with foliage tothe ground; 1977 – after serious rabbit attack; 2002 – surviving bushes (note 1metre rule). (Photographs by Lena Ward).
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Figure 18 – Juniper in the process of being shaded out by successionalchange to Yew woodland at Stockbridge Down, Hampshire, 1985.(Photograph by the late J.A. Grant, with kind permission of Lena Ward).
Figure 17 – Basal damage to Juniper by rabbits at Porton Down, Wiltshire. (Photograph by the late J.A. Grant, with kind permission of Lena Ward).
so far recorded in the UK reached about 6 m at Holystone Burn in Northumberland. The maximum height for a Juniper in Norway was 18 m. The Borders Forest Trust Survey (1997) found that the maximum spread can be considerable - an individual bush covered 35 m2.
Figure 19 – Dead and dying Juniper in an old population at Blakes Firs, Porton Down, Wiltshire, 1991. (Photograph by Lena Ward).
Figure 20 – The oldest recorded Juniper in the U.K. growing in Teesdale in1987, with 255 annual rings. (Photograph by the late J.A. Grant, with kindpermission of Lena Ward).
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The life span of Juniper in open unshaded conditions is about 100-120 years on the southern chalk, and stands with many dead and dying bushes can be found where the population was roughly even-aged (see Figure 19). In the south a bush with 130 annual rings has been recorded at Porton Down and one with 145 annual rings has been found on the Cotswold limestone. The oldest Juniper so far recorded by Ward had 255 rings (and therefore a minimum age of 255 years) and was from Teesdale (see Figure 20). No doubt other older specimens will be found. There is a suggestion that faster-growing bushes have shorter life spans than slower-growing ones (Ward, 1981). Many Juniper plants, however, do not live to their maximum life span as they are shaded out by encroaching scrub and secondary woodland. This can happen relatively quickly – in as little as 30-50 years in vigorous mixed scrub stands with Hawthorn, Ash, Whitebeam, etc. Stands amongst Yew live longer as Yew is so slow growing but are inevitably killed by the dense shade. Nearly all the old Juniper (in southern England) have serious cankers and rots in the roots and butts. Although there have been no studies to date of the life span of Juniper in Scotland, in more extreme situations it probably lives longer than Juniper in the south of England (MacDonald, pers. com.). However, it is very difficult to age bushes of J. communis ssp. nana because of the form of the stems, the way wood is laid down and the occurrence of layering. Juniperus communis ssp. communis is a dioecious plant with the sexes occurring on different bushes. The sex ratio within populations on the chalk, especially those that are grazed or damaged by rabbits, is usually biased in favour of males. Ward (1981) recorded a ratio of 1 M: 1.26 F (+ 0.49 unknown sex) in young Juniper at Porton Down in 1971, but after rabbit attacks during the late 1970s the sex ratio became 1 M: 0.58 F (+ 0.17 U). For the same years on this site a very old Juniper stand had ratios 1 M: 0.62 F (0.38U) in 1971 and 1 M: 0.59 F (0.26 U) in 1979. Joensalo (2000) also found that females of Juniperus communis ssp. nana were differentially grazed. However, this bias to females does not always hold true. Falinski (1980) observed that females predominated in very old stands, while Marion & Houlé (1996) did not find any consistently obvious differences in sex ratios and growth. In Scotland, although Sullivan (2003) attempted to determine sex, this was not possible for 79% of plants surveyed because of the relatively short period of time in which the male cones were present. Males are therefore under-represented in his analysis. However, the measured proportion of female plants was only 15%. There is relatively little information about metapopulation dynamics of Juniper. However, it is thought to be very important in the conservation of Juniper as it seems to be a mobile species, which rarely regenerates in the same place as the parent plants, but exploits new favourable situations within the general area of bird dispersal movements. This is less obvious in a relatively long-lived plant like Juniper, as the persistence of the adult plants long after conditions have become unsuitable for regeneration means that conservationists have not always appreciated the rather different likely requirements. Taken in a broad sense, the general and progressive reduction in Juniper populations that we now observe means than the seed resources for new colonization are declining and new habitats cannot be exploited. These new habitats are nowadays rather rare and therefore we can predict the serious and future retrenchment of Juniper back to its heartlands and to extinction (Ward, 1981). Gene flow has been little studied, but the variability within populations is striking - a good feature for conservation. Greeve et al (1998) found that gene flow in the Netherlands populations were high, at 9.27 migrants per generation. Population size was not significantly correlated with the proportion of polymorphic loci, mean effective number of alleles or the mean observed heterozygosity. Their estimated parameters of gene diversity and gene flow showed that the Juniperus communis populations studied shared a common gene pool, regardless of the fact that most of them are isolated and disjunct today.
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Juniper, as the only native member of the Cupressaceae family, has a specialized plant feeding specific fauna of insects and mites in the UK, (Ward, 1977). There are 42 species including those from introduced ornamental Junipers. A few more species have been recorded since then, mostly introductions. These insects are distributed according to their individual climatic requirements. Some species are of Mediterranean origin and occur on downland Juniper, while others are of arctic alpine origin. Thus the fauna of Juniper in the Lake District and northern England is less interesting than that of either the south or the Scottish mountains. The different species are specialized to feed on all parts of the Juniper. Those feeding on berries and seeds may cause damage, but equally some species are in need of conservation themselves as the Juniper microhabitat declines. Juniper wood decays very slowly and has few wood-feeding insects; it appears to have chemical defences against both wood-rotting fungi and termites in southern Europe. In Scotland, Sullivan (2003) showed that the largest Juniper populations had most diseases and insect herbivory. This is also likely to apply to fungal pathogens. There are also specialized fungi, including in particular species of rust fungi, Gymnosporangium, which cause perennial galls on Juniper and sporulate in spring, with characteristic yellow finger-like projections (see Figure 21). These spores infect young growth of species of Rosaceae in summer spreading back to Juniper later in the season. The fungus usually only kills branches and does not often kill an entire bush. Gymnosporangium was not observed in prostrate Juniper in Scotland, although it was recorded in woodland and open ground Juniper (Sullivan, 2003). There are many other fungal species including some serious pathogenic species such as Juniper Blight Phomopsis juniperova. Juniper Blight occurred in 31% of all populations surveyed in Scotland (Sullivan, 2003), with an average of 23% of plants affected, making it the most commonly found cause of fungal disease. Juniper is also a good host for species of lichens but little is known about these.
Figure 21 – Gymnosporangium sp., arust fungus, at the perennial gallingstage with spores on yellow fruitingbodies, on Juniper in April, MardaleBanks, Cumbria. (Photograph by LenaWard).
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4 Habitat Requirements Juniper occurs in a wide variety of plant communities as it can grow on both acid and alkaline soils throughout the British Isles from sea level to the highest montane areas (Rodwell, 1991a, b & 1992). Juniper can be a pioneer element of all types of open ground communities except for those in wet areas, and is especially characteristic of free-draining soils. It is limited by shading, and cannot persist in dense woodland. The typical habitat of Juniperus communis ssp. communis in southern England is on chalk grassland, in open chalk habitats in quarries and in successional stages to woodland from these habitats. In the north of England there are also large stands on limestone pavements and scars. Juniper also occurs abundantly in some acidophilous heath communities. The most important in England is that of Borrowdale volcanic slates, followed by Bannisdale slates / Coniston flags, and whin sill (dolerite) and millstone grit - important in the Teesdale area. Often Juniper occurs in areas that were mined in the past. There are also smaller stands on the sides of eroded streams, e.g. in Northumberland. In the highlands of Scotland Juniper is common in open pine woodlands as in the Caledonian Forest, and also in birch woodlands. In some areas there are almost pure Juniper stands with very few tree species. There are also the uncommon but important Juniper sites on dunes in northeast Scotland recognized by the EEC Habitats Directive. Juniperus communis ssp. nana is scattered in exposed habitats through northwest Scotland and the Outer Isles.
Figure 22 – Juniperus communis ssp. communis in Pine woodland (NVC W19) inthe Caledonian Forest, Loch Eilen, 1993. (Photograph by Lena Ward).
4.1 COMMUNITIES & VEGETATION National Vegetation Communities (NVC) communities in which Juniper is a dominant woody species are the most important for conservation (Ward, 1994). These occur in woodlands, grasslands and heaths. The three major communities with Juniper as the
dominant species are described first, and then other communities mentioned in Rodwell (1991a, b & 1992) are listed briefly. A full detailed list of all 66 communities and sub-communities from the original data in all samples used in the construction of the NVC is provided by Wilson & King (2001). IMPORTANT JUNIPER COMMUNITIES W19 Juniperus communis ssp. communis - Oxalis acetosella woodland Juniperus communis ssp. communis is the most abundant woody species in this community though some stands have an open over-canopy of Betula pubescens (Downy Birch). The Juniper may be patchy, but the bushes are not widely scattered. The bushes may have very diverse forms, and can be affected by browsing by stock or deer. Vaccinium myrtillus and Calluna vulgaris and ferns may be prominent. The grasses present are Agrostis capillaris, A. canina and Anthoxanthum odoratum, while Oxalis acetosella, Galium saxatile and Potentilla erecta are common. This is a community of higher altitudes in the colder parts of northwest Britain on a wide variety of soils (Rodwell, 1991a). All the soils are free draining, but are not extremely dry because of the heavier rainfall in these areas. The community is represented in northern England, although its greatest area of abundance is in the Scottish Highlands. Whether it is a climax montane scrub is uncertain because of past destruction of the tree canopy in which pine and birch would have been abundant. Where trees are not present at lower levels then seral processes do not occur and the community is like a climax community. W21 Crataegus monogyna-Hedera helix scrub This is a very mixed and extensive community including most of the seral thorn scrub and hedges in the British Isles. It is especially characteristic of the chalk and limestones of southern England (Rodwell, 1991a), though there are examples around Morecambe Bay. Juniper is more often found in the Viburnum lantana sub-community, on the shallower, drier soils on steeper more exposed slopes than the scrubs where Crataegus is dominant. The diverse chalkland woody species such as Viburnum lantana, Cornus sanguinea, Ligustrum vulgare and Rhamnus catharticus are common. The scrub is more obviously seral than in the north, although succession may still be slow on very impoverished dry soils or sites where few trees invaded early on (Duffey et al, 1974). In quite a number of examples, grazing by rabbits or stock has prevented seral progression, and the Juniper then may be the major scrub species in CG7 (see below). Eventually bushes may die in the open of old age and disease. H15 Calluna vulgaris-Juniperus communis ssp. nana heath. Prostrate Juniper occurs in a variety of dwarf sub-shrub heaths in Britain, but is more or less consistently dominant in the sub-shrub mat of the Calluna-Juniperus heath. Here it is accompanied by a distinctive element of oceanic hepatics, and Calluna vulgaris and Erica cinerea are especially frequent. This community is found at moderate altitude in the cool ocean climate on the western coast of the northwest Highlands and Islands (Rodwell, 1991). It is best developed on cool, shady slopes blown clear of snow, and is replaced at the junction of the sub-alpine and lower alpine zones by Juniperus-Oxalis scrub. There are stands, which are floristically and physiognomically intermediate between these two communities, with Juniper difficult to assign between communis and nana. This is a transitional community on the junction of the low alpine and sub-alpine zones. It can be seen as the north west Highland equivalent of the Juniperus-Oxalis scrub of the east central Highlands, though there it is ssp. communis that colonizes up to the limit of the forest zone.
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OTHER WOODLAND, GRASSLAND & HEATHLAND COMMUNITIES WITH JUNIPER W11 Quercus petraea-Betula pubescens-Oxalis acetosella woodland Juniperus communis ssp. communis occurs in the more open areas of this community, its increasing abundance often marking transitions to stands of the Juniperus-Oxalis woodland in the north. W17 Quercus petraea-Betula pubescens-Dicranum majus woodland In Eastern Scotland Juniperus communis ssp. communis may occur in this woodland community, which can form mosaics with the more calcifugous stands of the Juniperus-Oxalis woodland. W18 Pinus sylvestris-Hylocomium splendens woodland Juniper can be found as scattered bushes or in small patches in this community, and may become locally dominant in the absence of Pinus. These stands are best seen as mosaics with Juniperus-Oxalis woodland. They are a characteristic feature of higher altitude situations in eastern Scotland. CG7 Festuca ovina-Hieracium pilosella-Thymus praecox/ pulegioides grassland Juniper invades along with other woody plants in the very early succession of the open vegetation of the Cladonia sub-community, and may form an open scrub as at Porton Down (Wells et al, 1976). Juniper may also invade the more typical limestone grassland communities in the south on the chalk or oolite. Where there are larger numbers of bushes that grow on to become the dominant element with other shrubs, this grades into the Crataegus monogyna-Hedera helix scrub described earlier. Juniper can persist as scattered bushes in limestone grasslands, but under severe grazing pressures may eventually become senescent and die without replacement by regeneration. CG9 Sesleria albicans-Galium sterneri grassland Although Juniper is not included in this community in Rodwell (1992), it is considered an important colonist in some of these grasslands. The community occurs on free-draining but moist soils usually over drift-free Carboniferous limestone in the submontane and montane areas in the northern Pennines. The climate is cooler and wetter than that of the southern lowland calcicolous grasslands. CG13 Dryas octopetala-Carex flacca heath Juniperus communis approaching ssp. nana in its procumbent habit occurs in the Salix repens-Empetrum nigrum ssp. nigrum sub-community. This community is restricted to calcareous lithomorphic soils in the cool oceanic lowlands of northwest Scotland. H7 Calluna vulgaris-Scilla verna heath Juniper is very rare in this community in the area of the Lizard Peninsula in Cornwall, and is probably ssp. communis although small in size. Elsewhere this community occurs around the coast, and is the extreme maritime fringe of British sub-shrub vegetation. H12 Calluna vulgaris-Vaccinium myrtillus heath Scattered bushes of Juniperus communis ssp. communis can be found in some situations around the eastern Highlands in this community. This is the typical sub-shrub community of acid to circum-neutral, free-draining mineral soils in the cool and wet sub montane zone. Sometimes found in association with Juniperus-Oxalis scrub, the community is widely distributed in southeast Scotland, the Lake District, parts of Wales and the southwest peninsula, and the North York Moors. H14 Calluna vulgaris-Racomitrium lanuginosum heath (dwarf mountain heath) This community includes sparse records of Juniperus communis generally as ssp. nana. It is the typical shrub community of base poor soils at moderate to fairly high altitudes in the cool oceanic climate of the mountains of northwest Scotland. It sometimes gives way
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at lower altitudes to prostrate vegetation in which J. communis ssp. nana becomes very common and often co-dominant with the stunted heath. H16 Calluna vulgaris-Arctostaphylos uva-ursi heath Juniperus communis ssp. communis occurs very occasionally in this community in the east central highlands. H17 Calluna vulgaris-Arctostaphylos alpinus heath Juniperus communis ssp. nana occurs in some stands, but the generally small contribution of this plant to the vegetation here helps distinguish it from the Calluna-Juniperus heath. The community is confined to northern Scotland. H20 Vaccinium myrtillus-Racomitrium lanuginosum heath Juniperus communis ssp. nana occurs locally in this community type, which is strongly centred in northwest Scotland on humic base-poor soils on fairly exposed slopes at moderate to high altitudes. In the former, J. communis ssp. nana occurs in the Viola riviniana-Thymus praecox sub-community. H21 Calluna vulgaris-Vaccinium myrtillus-Sphagnum capillifolium heath Juniperus communis ssp. nana (and Arctostaphylos species) are occasional in this community of mixed sub-shrubs. In fact their absence helps separate the community from the Calluna-Juniperus heath. The community occurs widely but locally through the northwest Highlands and on the island of Skye.
4.2 SUMMARY OF HABITAT REQUIREMENTS The habitat requirements of Juniper in Britain are described below in Table 4. Table 4 - Habitat features important to Juniper communis ssp. communis in Britain.
TYPE DESCRIPTION
Physical and topographical
Steep eroding slopes. Bare ground. Seedlings may appear during and just after severe grazing, but only persist when grazing by domestic stock/rabbits is reduced or absent. Older plants can withstand grazing and browsing. Seedlings do not tolerate long dry periods in summer.
Vegetational and structural
Production of fertile seed is more reliable from young bushes. Open/bare ground communities for regeneration and persistence (does not normally regenerate in deep grassland). Full light to slight shade only, dies in later stages of succession, therefore not in woodland unless very open, or at and above the tree line. Large stands required to ensure the survival of associated insects.
Chemical Thin nutrient poor soils either acid or alkaline.
5 Management Implications The regeneration of Juniper is the most critical factor for management of lowland Juniperus communis ssp. communis. Of course, it will not matter if there is no regeneration at any one time, but only if this state continues throughout the reproductive life span of a stand of Juniper. At the present time, most of our younger
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Juniper populations in England date back to a regeneration phase that was caused by the loss of rabbits from myxomatosis in 1954-55 (preceded by very heavy grazing) creating ideal open ground conditions for young seedlings. However, considering the life span of Juniper is somewhere between 100-130 years in the south, and knowing that the majority of current Junipers are approaching 50 years in age with declining seed production, it is obvious that regeneration should be promoted vigorously now. The point is given even more force by the realization that Juniper in unmanaged mixed scrub stands in southern England will die much earlier because of shading. A detailed and tested prescription for management of natural regeneration is not yet available. There have been a number of not very successful experiments, but deductions from their results and from general knowledge suggest the following requirements for chalk downland Juniper:
A nearby population of healthy, fruiting Junipers.
Open bare ground or short slow-growing vegetation and nutrient poor soils produced by:
removal of nutrient rich topsoils and competing vegetation. continuous heavy grazing followed by no grazing. cutting and/or burning to remove vegetation and reduce nutrients. disturbance of soils to create open patches.
After seedlings appear then reduction/prevention of grazing by rabbits or
domestic stock for about 10 years. Light grazing is possible, but not fully recommended, in this case summer grazing is thought to be better than winter grazing (Fitter & Jennings, 1975).
Where Juniper is growing in good quality chalk grassland the requirement to reduce grazing and disturb the ground may conflict with best practice for the grassland management and control of other scrub species. In such cases it is therefore suggested that a nearby area, which might currently be arable, can be managed for Juniper regeneration. In northern England and Scotland, increasing levels of natural regeneration seem to rely on ground disturbance followed by initial protection from grazing where grazing levels, by sheep, deer or rabbits, are high. Fences, where used, need to be marked to avoid bird collisions and sited below the skyline, but the situation also needs to be monitored as the growth of rank vegetation will eventually create conditions that are unsuitable for Juniper. Otherwise, emerging seedlings may have to be guarded against voles and other herbivores, (Furness, in press). In some areas Juniper may be regenerating continuously rather than in a pulse related to a change in land use. In these instances grazing is the most important factor in survival. Problems are obvious where the bushes and seedlings are only surviving in very low numbers (Gilbert, 1980) or are on very steep rocky slopes or in boggy areas where grazing is prevented. This situation is common in northern England and in Scotland, and has lead to recommendations for a reduction in numbers of grazing animals (Miles & Kinnaird, 1979a & b). On some sites it may be impractical to promote natural regeneration, which should be the best aim of conservation as Juniper is set in its true ecological context. In cases where Juniper has small or unhealthy populations with no regeneration, then cuttings need to be taken from the extant Juniper on the site or new plants reared from their available seed. Ideally seedlings are preferred as they retain genetic diversity and techniques have improved recently to increase germination and survival rates (Furness,
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in press). However, where bushes are old and no longer producing sufficient viable seed, then cuttings will be necessary, if only to start to produce berries and seedlings. Cuttings can be obtained relatively easily using standard methods of horticultural mist propagation, and 10 cm long hardwood cuttings should be taken in February or March (Broome, 2003). The cuttings are grown on for only about 2-3 years and can then be planted out, care being taken to grow them in soils which reflect the intended new habitat and to spread the root ball properly. These cuttings should be taken from both male and female plants with a preponderance of the latter. Broome (2003) found that cuttings taken in February showed the highest survival rate (67%). To preserve genetic diversity at least 30 bushes should be used (Borders Forest Trust, 1997), although material should be gathered from single populations or clusters of populations within 1 km to preserve genetic integrity and any advantages this may have on environmental adaptations (Broome, 2003). There is also some suggestion that taking cuttings from lateral shoots affects the ultimate form of the bushes, which may sometimes be less erect than those grown from seed. Juniper bushes grown from cuttings seem to be just as successful in both growth and reproduction as naturally occurring Juniper, but in some cloned plants there is an effect on aging and individuals become senescent earlier. Where seed is collected and grown on, levels of viability should be checked before any sowing as otherwise too few seed may be sown. There are techniques for separating out the empty seed (Warren & Britain, 2001; Furness, in press), although a percentage of seed should be checked in the field prior to collection to ensure higher levels of viable seed. Cutting through the berry at its equator with a sharp blade will identify viable seeds by a creamy white opaque material inside the seed casing (Furness, in press). If 75% of tested berries have viable seed then collection is worthwhile. Established populations of Juniperus communis ssp. communis of over about 20 years may be set in grazed grassland and provided the grazing is not intensive and animals do not lean on the bushes and cause damage, then Juniper managed in this way is likely to survive to its full life span, becoming old and senescent in situ as on chalk grassland. Some rabbit damage to the base of the trunks can occur, but seems to be tolerated in these older bushes, although there may be repercussions from fungal diseases after many years. Deer may suppress the growth of young bushes. Conversely, if grazing is intensive and continuous over many years, then damage to Juniper can be serious as its loss is progressive and stands are fragmented into communities of scattered individuals (Scottish Borders Trust, 1997). In lowland Britain Juniper is likely to be part of a successional community leading to woodland, and although this natural process should be included as part of Juniper ecology on large scale nature reserves, it might be necessary on small sites to prolong the reproductive life of existing Juniper bushes present. One aspect of this is to prevent the initial invasion of other woody plants by the removal of their seed parents in the local vicinity. This has historically happened on very open chalk downlands where monocultures of Juniper resulted from the absence of other seed-parents in hedges and other scrub. To simulate this at Bulford in Wiltshire an arbitrary distance of 100 m to isolate the Junipers is proposed (Ash, 1996). In other stands the woody plants already present and competing with the Juniper can be removed. This should best be done during the earlier years of growth as once Junipers are elongated by competition for light then they become unstable when the other woody plants are removed. In any case there is no re-sprouting from the base. Spindly plants are vulnerable to serious damage by wind and snow (see Figure 23). The specific associated fauna and flora of Juniper should be taken into account in conservation management. Each area of the country should have conserved areas to include the local geographical representation of the specific species, with the southern chalk downland and the highlands of Scotland being particularly important. The size of the colony of Juniper required to maintain populations of dependent insects is important
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(Ward & Lakhani, 1977b). Only very large sites with more than 3000 bushes in southern England were predicted to maintain all 15 of the commonest insect species with the probable addition of a few of the rare species. Even in 1977 there were only four of these large Juniper areas remaining. Insect species were progressively lost as Juniper colony size decreased. Colonies of 500-1000 bushes might have 11-15 species, while those of 100-500 might have 8-14 and those with 50-100 bushes had 7-11 species. Higher numbers are related to long history of the presence of Juniper on the site. Those insects that depend on the microhabitat of berries - which will only be found on about half of the Juniper plants present - are particularly vulnerable. One fruit-feeding insect has now become extinct on the greatly depleted Juniper on the North Downs.
6 Threats / Factors Leading To Loss or Decline or Limiting Recovery Table 5 summarizes the threats to the survival of Juniper in Britain. Problems with failure of regeneration are the most serious threat. For Juniper colonies in the south, surveys by Ward (1973) and Plantlife International in 2001-2 can be compared (see Table 6). In this small sample shading and succession were the greatest threat, with old age the next. An increase in rabbit damage had occurred by 2002, but Juniper in afforested areas was no longer affected. Table 5 - Threats to the survival of Juniperus communis ssp. communis in Britain.
Type Threat
Regeneration Change of land use to intensive agriculture. Few areas abandoned to natural succession. Lack of suitable nutrient-poor new sites. Too many rabbits/domestic animals/deer. Lack of good population of seed parents. Climate change with drier weather in spring and summer.
Figure 23 – Weak Juniper that was freed fromengulfing but supporting scrub andsubsequently damaged by heavy snow,Peperbox Hill, Wiltshire, 1987. (Photograph byLena Ward).
Type Threat
Existing populations
Damage to young bushes by rabbits (browsing and ring barking). Damage to older bushes by heavy cattle browsing (though this might benefit regeneration by creating patches of bare ground). Damage by deer browsing. Burning. Afforestation. Development. Successional change (faster in southern England). Age, health and senility. Loss of specific insects caused by reduction in Juniper numbers.
Table 6 - Direct comparison of percentages of perceived threats to 98 colonies in 1973 and those still present in 2002 in Wiltshire, Bedfordshire, Sussex and Hertfordshire (from the database for the ongoing survey by Plantlife International).
NO. OF THREATENED SITES TYPE OF THREAT 1973 2002
Total colonies
98 (9*) 51(47†)
Shading and succession 25 35 Old age 16 10 Rabbit damage 2 16 Scrub clearance for other management
2 10
Plantations 4 0 Cattle damage 4 4 Housing and development 2 2
* new sites not present in 1973. † sites lost by 2002. The serious implications of over-grazing and progressive damage have already been mentioned in Section 5 and apply with more force to northern populations of Juniper where successional features are usually less relevant. Burning is a particular threat to Juniper on moorlands (McVean, 1961) and heathlands and occurs occasionally also on some limestone commons. The habitat resulting after burning may very occasionally be suitable for regeneration, as occurred at Tynron Juniper Wood NNR (Sykes, 1976), but repeated burning is disastrous. In a Scottish study, Common Juniper was killed by 800oC heat treatment when heath was burned. Plants made only "feeble re-growth" when burned at 600oC. However, following treatment at 400oC, new shoots were produced (Mallik & Gimingham, 1983). However, anecdotal evidence from northeast Scotland suggests that where muirburn is controlled so that Juniper bushes are not burnt then regeneration will occur in the bare patches. Adherence to the Muirburn Code allows the persistence of Juniper populations, and where conducted well will allow regeneration, although Sullivan (2003) has illustrated the exclusion of Juniper in repeatedly burnt areas in Scotland.
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7 Current Conservation Measures
7.1 N SITU MEASURES IJuniper occurs on many protected areas: National Nature Reserves (NNRs), Sites of Special Scientific Interest (SSSIs), Special Areas of Conservation (SACs), County Wildlife Trust Reserves, Local Nature Reserves, National Trust properties, etc. Some statistics are presented in Table 7. Table 7 - Incomplete data about the statutory protection of Juniperus communis ssp. communis in the U.K.
PROTECTION COUNTRY NO. OF SITES NOTES
NNR
England Scotland Wales Ireland
SSSI England Scotland Wales Ireland
94* 14**
SAC England Scotland Wales Ireland
13 11**
0 0
EU habitats 5130 and 2250
*35 SSSIs identified as Juniper scrub W19 and W21d (Mortimer et al, 2000) **Scottish data is based on notified features only and is a minimum number therefore for protected sites that contain Juniper. Special attention is paid to SACs designated under the Annex I EEC habitat directive 1992.
Juniperus communis formations on heaths or calcareous grasslands (EU code 5130). There are 15 sites which occur in the A and B categories (A = Outstanding examples in a European context. B = Excellent examples, significantly above the threshold for SSSI/ASSI notification but of somewhat lower value than grade A sites). 2 sites are in the C category (C = at least national importance (i.e. usually above the threshold for SSSI/ASSI notification on terrestrial sites) but not significantly above this, but not the primary reason for SACs being selected). 14 sites are in the D category (D = below SSSI quality occurring on SACs. These are non-qualifying features (“non-significant presence”) and are not the primary reason for SACs being selected.
Coastal Dunes with Juniperus spp. (EU code 2250). Two sites in Scotland
are awarded the Grade A category (Dornoch Firth with Morrich Mhor and Invernaver). 10 localities for this habitat are known from northern Scotland.
In the comparison of conservation schemes and Juniper distribution, the situation is greatly improved from 1973 when Ward estimated the conservation status of Juniper in the south of England. Although summary data are not available, it is thought that all larger sites and most of the small sites now have some level of conservation management. CURRENT CONSERVATION SCHEMES There are a lot of initiatives for the conservation of Juniper and virtually all sites with large numbers of Junipers have conservation management plans. Smaller populations as
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on Wildlife Trust Reserves and SSSIs are by no means forgotten and there are many schemes everywhere for the safeguarding the extant populations and for additional planting for the future using cuttings or attempting to promote regeneration from seed. The following are among the most important current schemes for Juniperus communis ssp. communis:
The Salisbury Plain EU LIFE project is particularly important for Juniper in southern England and scrub clearance among Juniper at Porton Down (Grade A SAC and SSSI) is illustrated in their Newsletter (2003).
National Trust for Scotland Ben Lawers Montane Scrub project includes work with
Juniper.
Habitat Action Plan for Native Pinewoods in Scotland where Juniper is an important element.
Habitat Action Plan for Coastal Sand Dunes.
Links to Local Action Plans are listed in the Action Plan for Juniper for 7 areas in
England, 8 in Scotland and 2 in Wales.
7.2 EX SITU MEASURES SEED BANKING This is not considered important at the present time. MATERIAL HELD IN CULTIVATION Numerous specimens of Juniper, including Juniperus communis sub-species and cultivars, are held in Arboreta and Botanic gardens through the world. In the UK special mention may be made of Bedgebury Pinetum (Kent), Cambridge University Botanic Garden and the University of Oxford Botanic Garden.
7.3 RESEARCH DATA A group of researchers in Spain led by D. Garcia, University of Granada, is
actively researching the reproductive biology including dispersal by birds.
Work on DNA fingerprinting and the taxonomy of Junipers is making excellent progress under the leadership of R.P. Adams, Baylor University, Texas.
There is ongoing research into long-term population changes in demography,
health and age at death at Porton Down by L.K. Ward, CEH Dorset.
Forestry Commission work on Juniper seed germination and the production and use of cuttings by A. Broome was published in 2003.
Work for the Ministry of Defence under the Salisbury Plain LIFE project that began
in 2001 is mainly management for conservation of Juniper and other wildlife, but there will be research and monitoring elements to assess the results of management, and some work on sowing seeds of Juniper and on the fauna. (Project Manager - S. Davis, English Nature).
Plantlife International is currently re-surveying some southern counties to look at
changes since 1973 (M. King, P. Wilson & L.K. Ward).
7.4 MONITORING JUNIPER & THE COMMON MONITORING STANDARD Plantlife International is re-surveying the Juniper sites originally recorded by Ward in England following her basic methodology of using the Juniper colony for comparison and counting the number of bushes. The colony was defined as ‘an area of Juniper where no sharp topographical distinction in the age structure of the bushes can be detected, and where the other vegetation is uniform. The colony may be fragmented from a larger area, and it is under the same ownership and management’ (Ward, 1977b). It is particularly difficult to make accurate counts of large populations, and there are inaccuracies in the earlier work. Greater efforts are therefore being made to grid populations and spend more time assessing and mapping the populations. This needs to be done in winter when Juniper can be seen more clearly. Populations mixed with Gorse (Ulex spp.) are harder to assess. This methodology is probably not suitable for Juniperus communis ssp. nana, which cannot be easily seen in some montane communities. It must be recognized that it is impossible to be fully accurate, as individual Juniper bushes cannot be defined with certainty when growing close together, especially if there is vegetative reproduction. Improvements have been made in the new survey including more details about the populations, management conditions, habitat and damage (Wilson & King, 2001). The field information recorded is entered onto a new survey form, and the old and new data have been incorporated into a database running in ACCESS. So far the comparison of the colonies has worked quite well. The greatest difficulty is on large sites where the earlier survey has been more inaccurate. Scottish Natural Heritage funded the random stratified survey of Juniper across Scotland in 2002-2003 and the methodology used was designed by SNH with Forest Enterprise who also used it in a survey of Juniper on FE-owned land across Scotland. This methodology now informs Site Condition Monitoring for Juniper in Scotland.
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the requirement for the degree of B.Sc. in Ecological Science with honours in Wildlife and Fisheries Management. May 1998.
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9 Acknowledgements Miles King for discussions and information in the compilation of this dossier. English Nature for data and information. Henry Arnold supplied data and advice about mapping of Juniperus communis and its sub-species. Jill Sutcliffe for comments on the text.
10 Contacts Plantlife International The Wild-Plant Conservation Charity 14 Rollestone Street Salisbury Wiltshire SP1 1DX Tel: 01722 342730
Andrew Byfield – [email protected] Deborah Long – [email protected][For upland Juniper enquiries] Amanda Miller - [email protected]
Lena K Ward CEH [email protected] Contact Point Alice Broome Forest Research, Northern Research Station, Roslin, Midlothian EH25 9SY Tel: 0131 445 2176
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11 Links ARKive species web page for Juniperus communis: http://www.arkive.org.
Plantlife International’s Back from the Brink (species recovery) programme is supported by English Nature, Scottish Natural Heritage & the Countryside Council for Wales. Work on Juniperus communis is supported by:
Original draft by Lena Ward
Edited by Plantlife International First draft dated May 2003
Last revised 20 August 2004
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