Juniperus Communis L

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 22 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). 23 Figure 12 – Male cones of Juniperus communis in spring with cone scales and pollen sacs. Left – pollen sacs full; right – pollen sacs discharged. (Photographs by Lena Ward). Figure 14 – 1st year Juniper berries Figure 13 – Receptive droplets on (green) and 2nd year berries (purple) in female cone flowers of Juniper in autumn. (Photograph by Lena Ward). spring. (Photograph by Lena Ward). Figure 15 – Sections of 1st year (green) and 2nd year (purple) Juniper berries in autumn. (Photograph by Lena Ward). 24 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 25 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

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