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Juglans regia 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Juglandales Juglandaceae

Scientific Name: Juglans regia L.
Regional Assessments:
Common Name(s):
English Common Walnut
Taxonomic Source(s): The Plant List. 2017. The Plant List. Version 1.1. Available at: http://www.theplantlist.org/.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2017
Date Assessed: 2017-01-12
Assessor(s): Rivers, M.C. & Allen, D.J.
Reviewer(s): Oldfield, S.
Justification:
Juglans regia is native to central Asian and southern European countries. The species native range is not fully classified as the species has been widely cultivated for a number of centuries and due to this cultivation the species has become more widespread. It is assessed as Least Concern as it has a large extent of occurrence (EOO). There are no population estimates, but it is likely to be large. The threats to this species include a number of pests and diseases and genetic degradation from selective logging and hybridisation. The scale of the impact of these threats is unknown.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Juglans regia is native to central Asia and some parts of Europe. Within central Asia there is an estimated 8,000 km2 of J. regia forest; over half of which occurs in Kyrgyzstan, followed by Tajikistan and Uzbekistan with the remainder in Turkmenistan (Molber et al. 2011). Within Europe the species native distribution is hard to classify as the species has been widely introduced and cultivated. It is most commonly thought to be native to the Balkan Peninsula and potentially Spain. The species has also been introduced to China, Australia and the USA where it is an important crop species. The species has a large EOO.
Countries occurrence:
Native:
Afghanistan; Armenia; Azerbaijan; Bosnia and Herzegovina; Bulgaria; China (Tibet [or Xizang]); Croatia; Georgia; Germany; Kazakhstan; Kyrgyzstan; Pakistan; Tajikistan; Turkmenistan; Uzbekistan
Introduced:
Austria; Belgium; France (Corsica, France (mainland)); Greece (East Aegean Is., Greece (mainland), Kriti); Italy (Italy (mainland), Sardegna, Sicilia); Luxembourg; Spain (Spain (mainland)); Switzerland; United Kingdom (Great Britain)
Present - origin uncertain:
India; Nepal; Romania; Serbia; Turkey
Additional data:
Lower elevation limit (metres):600
Upper elevation limit (metres):3000
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The population is widespread and likely to be large however there is no known population figures for the species. It is also difficult to differentiate between native and cultivated populations. Some local populations can be limited in size (de Rigo et al. 2016) and decline within central Asia has been commented on but there are no official numbers for this (Molnar et al. 2011).
Current Population Trend:Unknown
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:Juglans regia is a large tree, growing to a height of 35 m with a large crown. It is able to live for up to 70 years (Molner et al. 2011). The species requires a long warm season for growth and is sensitive to winter and late spring frosts (Wani et al. 2016). The species prefers moisture and can only survive a short period of drought. The species requires a lot of light and prefers deep soil for optimal growth (Wani et al. 2016). Juglans regia is not frequently found in mixed forests, it occurs in large un-mixed stands or in isolated zones. There are also many cultivar species of Juglans regia.
Systems:Terrestrial

Use and Trade [top]

Use and Trade: Juglans regia is an important food crop. Whole walnuts and walnut products (such as walnut flour) are of high popularity as a health food as they contain an antioxidants and antimutagenics and as a super food due to high protein content (Wani et al. 2016). The nuts can also be used to produce oil for cooking or for use in cosmetics. Juglans regia also has a range of uses in traditional medicine across the globe, with different parts of the plant having different medicinal properties. The species is sort after for its wood which is strong, durable and resistant to pests, heat and cracking. Due to these properties the species is used to produce veneers, furniture and craft pieces (Molnar et al. 2011).

Threats [top]

Major Threat(s): Within central Asia there has been historical felling of walnut forests due to expansion of agriculture and for timber. In Kyrgyztan between 1897 and 1995 200 km2 of walnut forest was cleared however this does include the cutting of Pistacia vera and Prunus dulcis within the same range (Molnar et al. 2011)Presently the species is threatened by fruit collection, cutting and livestock grazing. Within Europe the species is susceptible to fungal disease caused by Armillaria mellea, Phytophthora cinamomii and P. cambivora which causes necrosis and summer leaf fall (de Rigo et al. 2016). Young trees are also susceptible to Walnut blight caused by Xanthomonas campetris pv. juglandis and the trees nuts are also susceptible to pests and diseases. There is concern of a loss of genetic variation due to habitat loss in native regions and the breeding of hybrid cultivars.

Conservation Actions [top]

Conservation Actions: In Central Asian germplasm of Juglans reiga cultivars is held and used for research across the globe (Molnar et al. 2011). The species is held in 200 ex situ collections from across the globe (BGCI 2017). Within central Asia the species is considered Near Threatened (Eastwood et al. 2009), Endangered in Albania (National Red List) and Least Concern in Europe (Allen 2016). Outside its considered native range the species is considered Least Concern in Switzerland (Moser et al. 2002) and Luxembourg (Colling 2005). There is a need for research to understand the impact of pests and diseases on the Juglans regia populations, especially within the species Asian range. The possible reduction in genetic variation should also be investigated.

Citation: Rivers, M.C. & Allen, D.J. 2017. Juglans regia. The IUCN Red List of Threatened Species 2017: e.T63495A61526700. . Downloaded on 18 December 2017.
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