Juniperus cedrus | Threatened Conifers of the World (en-GB)

Cupressaceae

Juniperus cedrus Webb & Berthol

Endemic to the Canary Islands and Madeira, where it often occurs at high altitude clinging on to exposed rock outcrops. Threats include grazing and fire.

Description

Habit

Mostly occurs as dioecious shrub, often at high altitudes, rarely seen as a tree to 20m tall. Branches spreading or ascending, crown broad and irregular, young trees more pyramidal. Bark orange-brown, exfoliating in long stringy strips.

Foliage

Often sparse with characteristically spreading, pendulous branchlets. Leaves borne in alternating whorls of usually 3.8–20mm long, 1.2mm wide, rigid and boat-shaped, straight with entire margins and pungent at apex, stomata in two conspicuously white bands occurring either side of the midrib on the upper surface.

Cones

Female cones 8–12mm, globose, borne in the axil of the leaves and orange-brown when mature in their second year. Male cones borne in the axils of the leaves, solitary or 1–2 per leaf whorl, 3–6mm long, 2–5mm wide, orange-brown.

Distribution

Restricted to the Canary Islands (Gran Canaria, Gomera, La Palma and Tenerife) and Madeira (from Pico Arieiro to Pico Ruivo). The population is estimated to be c.600 sexually mature individuals. In the Canary islands it is estimated that there are c.572 individuals and in Madeira there is a single sub–population with c.40 individuals (Sequeira 2010, unpublished data).

Habitat and Ecology

Canary Islands

This species has become adapted to a range of different habitats. In Tenerife and La Palma, J. cedrus occurs at the timberline (2200m), which characteristically has low precipitation and great diurnal temperature variation. Here the dominant vegetation includes the shrubs Spartocytisus supranubius and Adenocarpus viscosus. In contrast, on La Gomera, which is lower in altitude, (1150m.) the habitat is of laurel forest which has high levels of humidity as a result of the north-east trade winds. In Gran Canaria it only occurs on Montaña del Cedro, where it grows at altitudes of between 800–900m, here the temperatures are relatively warmer. At some of the locations (La Gomera and one location on Tenerife) there is evidence of regeneration but generally recruitment appears to be relatively poor. One factor that may be related to this, is the decline in ravens (Corvus corax) that are thought to have played a significant role in seed dispersal (Nogales, 1999; Remeu et al., 2009). Recent research has revealed that winter visiting Ring Ouzels (Turdus torquatus) also play a key role in seed dispersal (Remeu et al., 2009). Additional research has indicated that the Canary Islands subpopulations produce seed with relatively lower viability, possibly due to lower pollination rates resulting from fragmentation of stands (Remeu et al., 2009).

Madeira

The subpopulation on Madeira occurs on exposed rock faces above the laurel forest tree-line above 1,400m in altitude. Here it belongs to the Polysticho falcinelli-Ericetum arboreae (Capelo et al. 2004). The main components include: Erica maderinicola, Ilex perado, Laurus novocanariensis, Polystichum falcinellum, Vaccinium padifolium & Sorbus maderensis. In Madeira there have not been any studies to establish whether or not there is any regeneration, however since the removal of goats in recent years the vegetation recovery rates are very encouraging.

Human Uses

Historically in the Canary Islands the wood was exploited for its valuable, aromatic timber, and used by local people in carpentry for a various items of furniture, construction and for making boxes because of the wood's capacity to deter insect pests (Vieira 2002). Today, due to its rarity and protected status, J. cedrus is not utilized. In Madeira the wood was also widely used and even as early as in the 15th century there were already concerns about the excessive cutting of this species. Restrictions on harvesting this species were ineffective; according to Silva and Menezes (1946) there were still some small woods of J. cedrus by the end of the 19th century, but the tree had almost vanished by the first decades of the 20th century. Today the wood is no longer used, unless it is taken from cultivated sources.

The plant is extensively cultivated as an ornamental and used by the forestry service particularly along the Laurissilva Levadas (man–made irrigation channels and pathways).

Conservation Status

Global assessment

EN – Endangered, B2ab(ii,iii,v);C2a(i)

Global rationale

The total area of occupancy is calculated to be 29km². Presence and absence records are derived from recent, extensive surveys carried out between 2004 and 2009 (Elliot 2009, Rumeu unpublished data 2010, Sequeira pers.comm 2010). The total population is estimated to be less than 600 mature trees and no subpopulation contains more than 250 mature individuals. Subpopulations are regarded as severely fragmented; each is more than 60km from the next and no single subpopulation contains more than 50% of the total population. Regeneration in some subpopulations is poor or absent, possibly due to reduced seed set the decline of avian dispersers (Nogales 1999, Rumeu et al., 2009) and the effects of grazing. In some locations fires have led to the loss of mature individuals. Together, these factors contribute to a continuing decline in the quality of habitat and number of mature individuals. On the basis of these data, Juniperus cedrus meets the criteria for Endangered.

Global threats

Fire is the principal threat but grazing by goats, Barneby sheep and Muflón is very detrimental to regeneration. Other threats in Madeira include encroachment of Cytissus scoparius into the native habitat of J. cedrus. Global warming could affect the amount of seasonal rainfall and moisture from coastal fog.

Status – Canary Islands

EN Endangered, B2ab(ii,iii,v);C2a(i)

Rationale – Canary Islands

Area of occupancy is calculated to be 23km² with a total population of c.572 sexually mature individuals (Gran Canaria 12; La Palma 250; Tenerife 200; La Gomera100) (Elliot 2009). The population consists of 4 sub-populations each being relatively small and severely fragmented on 4 different islands the majority of which are more than 60km apart. There is clear evidence of decline in the extent and quality of the habitat due to fire and grazing.

Threats – Canary Islands

The most severe threat is fire with one of the worst recent incidences occurring in 2007 when a fire, which spread from a neighbouring Pinus canariensis forest, destroyed 30 old-growth trees in El Teide National Park on Tenerife. Regeneration is affected by grazing goats and the release of Barbery sheep (La Caldera de Taburiente National Park, La Palma). Muflón, were first released for hunting purposes in 1971 and are currently distributed in El Teide National Park and other surrounding protected areas (Rodríguez Luengo, 1993); these are now under control but the damaging effects from their grazing is still evident. Clearly a more recent potential threat is global warming which could affect the amount of seasonal rainfall and moisture from coastal fog.

Status – Madeira

CR Critically Endangered, B2ab(ii,iii,v);C2a(i);D

Threats – Madeira

Historically over-grazing, cutting and burning have been significant threats to the population. Although these threats are less today, the fast expansion of Cytisus scoparius following grazing is certainly a potential threat as it greatly increases the risk of fire.

Conservation Actions

Juniperus cedrus is a protected species in the Canary Islands and occurs in three National Parks; Parque Nacional del Teide, Tenerife; Parque Nacional de Garajonay, La Gomera; Parque Nacional de la Caldera de Taburiente, La Palma. The area affected by fire in Parque Nacional del Teide is being restored by using local provenance material (seed). In Gran Canaria, the subpopulation in Montaña del Cedro is included within the Reserva Natural Especial de Güigüi. This sub-population is considered as ‘in danger of extinction’ in the Regional Catalogue of Threatened Species (Ministerio de Medio Ambiente, 2009). On Madeira it is protected within the Parque Natural da Madeira (Natura, 2000) where all goats have been removed above 1400m under the authority of Direcção Regional de Florestas. This has had a positive effect on the general vegetation, but as J. cedrus is a slow growing tree, any benefits are unlikely to be seen for several years.

References and further reading

Adams R. P., Fontinha S. S., Rumeu B. & M. Nogales. (2010) Speciation of Juniperus cedrus and J. maderensis in the archipelagos of Canaries and Madeira based on terpenoids and nrDNA and petN-psbM sequences. Phytologia. 92: 44–55.
Borges, P. A. V., Abreu, C., Aguiar, A. M. F., Carvalho, P., Jardim, R., Melo, I., Oliveira, P., Sérgio, C., Serrano, A.R.M. & P. Vieira. (2008). A list of the terrestrial fungi, flora and fauna of Madeira and Selvagens archipelagos. Tipografia Peres, Amadora.
Capelo, J., de Sequeira, M., Jardim, R. & J. C. Costa. (2004). Guia da Excursão geobotânica dos V Encontros Alfa 2004 à ilha da Madeira. Quercetea 6: 5-45.
Elliot, M. (2009). The conservation status of Juniperus cedrus: An investigation. BSc (Honours Degree) thesis; Royal Botanic Garden Edinburgh and University of Glasgow.
Ministerio de Medio Ambiente. (2009). Catálogo Nacional de Especies Amenazadas: listado de taxones por categorías de amenaza. Ministerio de Medio Ambiente.
Moreno, J. C. (2008). Lista Roja 2008 de la Flora Vascular Española. Dirección General de Medio Natural y Política Forestal (Ministerio de Medio Ambiente, y Medio Rural y Marino, y Sociedad Española de Biología de la Conservación de Plantas), Madrid.
Nogales M., Hernández, E. C. & F. Valdés. (1999). Seed dispersal by common ravens Corvus corax among island habitats (Canarian Archipelago). Écoscience 6: 56-61.
Rodríguez Luengo, J. L. (1993). El muflón Ovis ammon musimon (Pallas, 1811) en Tenerife: aspectos de su biología y ecología. PhD Thesis. Universidad de La Laguna, La Laguna, Spain.
Rumeu B, Elias R, Padilla D, Melo C. & M. Nogales. (2011) Differential seed dispersal systems of endemic junipers in two oceanic Macaronesian archipelagos: the influence of biogeographic and biological characteristics. Plant Ecology. 212: 911–921.
Rumeu, B., Nogales, M., Elias, R. B., Padilla, D. Resendes, T., Rodríguez, A. Valdés, F. & E. Dias. (2009). Contrasting phenology and female cone characteristics of the two Macaronesian island endemic cedars (Juniperus cedrus and J. brevifolia). European Journal of Forest Research. 128(567–574).
Rumeu, B., Padilla, D. & M. Nogales. (2009). The key role of a Ring Ouzel (Tardus torquatus) wintering population in seed dispersal of the endangered endemic Juniperus cedrus in an insular environment. Acta Ornithologica 44(2): 199-204.
Rumeu Ruiz, B, de Sequeira, M, Elliot, M. & Gardner, M. (2011). Juniperus cedrus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 23 April 2013.
Silva, F. A. & C. A. Menezes. (1946). Elucidário Madeirense, Volume I. II. III., (Edição fac-símile de 1998, DRAC), Funchal.
Vieira, R. (1992). Flora da Madeira. O interesse das plantas endémicas macaronésicas. Serviço Nacional de Parques, Reservas e Conservação da Natureza, Lisbon, Portugal.