Juniperus flaccida



INTRODUCTORY


    Photo courtesy of James Manhart, Texas A&M University
AUTHORSHIP AND CITATION:
Sullivan, Janet. 2007. Juniperus flaccida. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

UPDATE OF THIS SPECIES REVIEW:
In March 2007, an extensive search was done to locate information on drooping juniper; see the list of source literature for the sources consulted. Little information was found, but that information has been added to the original review, and the references list has been updated. In substance, the review has changed very little from that originally published in 1993.
A. Scott Hauser, April 24, 2007

FEIS ABBREVIATION:
JUNFLA

NRCS PLANT CODE [41]:
JUFL

COMMON NAMES:
drooping juniper
Mexican drooping juniper
weeping juniper
weeping cedar
drooping cedar

TAXONOMY:
The scientific name of drooping juniper is Juniperus flaccida Schlecht. (Cupressaceae) [14,15,20,21,33,37]. There are 3 recognized varieties:

Juniperus flaccida var. flaccida Schlecht. [14,15]
Juniperus flaccida var. martinezii (Pérez de la Rosa) Silba
Juniperus flaccida var. poblana Martinez [14]

SYNONYMS:
Juniperus flaccida var. gigantea (Roezl) Gaussen
Juniperus gigantea Roezl p.p.
Juniperus gracilis Endl. [21]

LIFE FORM:
Tree-shrub

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
Information on state-level protected status of plants in the United States is available at Plants Database.

DISTRIBUTION AND OCCURRENCE

SPECIES: Juniperus flaccida
GENERAL DISTRIBUTION:
Drooping juniper occurs in the United States only in the Chisos Mountains of Big Bend National Park in Brewster County, Texas [14,15,20,21,33,37,44]. The major portion of its range is in Mexico and extends from Chihuahua and northeastern Sonora south to Oaxaca and Guatemala [14,27,27,33,37,38,44,48]. Drooping juniper is the most common juniper in Mexico [33]. Juniperus flaccida var. flaccida occurs from Big Bend National Park south into Coahuila and Oaxaca and westward to Sonora and Jalisco [3,15,47,48]. Juniperus flaccida var. martinezii is found only in Jalisco [14]. Juniperus flaccida var. poblana occurs from Jalisco eastward to Oaxaca [3,47]. The U.S. Geological Survey provides a distributional map of drooping juniper and its infrataxa.

ECOSYSTEMS [17]:
FRES35 Pinyon-juniper
FRES40 Desert grasslands

STATES/PROVINCES: (key to state/province abbreviations)
United States
TX

Mexico
Chih. Coah. Jal. Mich. Mor. N.L. Oax. Pue. Son. Tamps.
Zac.

BLM PHYSIOGRAPHIC REGIONS [9]:
13 Rocky Mountain Piedmont

KUCHLER [24] PLANT ASSOCIATIONS:
K031 Oak-juniper woodland
K054 Grama-tobosa prairie

SAF COVER TYPES [13]:
239 Pinyon-juniper
241 Western live oak

SRM (RANGELAND) COVER TYPES [36]:
504 Juniper-pinyon pine woodland

HABITAT TYPES AND PLANT COMMUNITIES:
In the Chisos Mountains, drooping juniper occurs in moist woodlands, pine-oak (Pinus-Quercus ssp.) woodlands, and oak scrub. Species other than those listed above with which drooping juniper occurs with include the tree species Mexican pinyon (P. cembroides), Grave's oak (Q. gravesii), gray oak (Q. grisea), Emory oak (Q. emoryi), alligator juniper (J. deppeana), Texas madrone (Arbutus xalapensis), and bigtooth maple (Acer grandidentatum); the shrub species Wright silktassel (Garrya wrightii), mountain sage (Salvia regla), fragrant sumac (Rhus aromatica), Harvard's century plant (Agave havardiana), foothill beargrass (Nolina erumpens), dwarf oak (Q. intricata), featherplume (Dalea formosa), and damianita (Chrysactinia mexicana); and the grass species pinyon ricegrass (Piptochaetium fimbriatum), Mediterranean lovegrass (Eragrostis barrelieri), bullgrass (Muhlenberis emersleyi), sideoats grama (Bouteloua curtipendula), and Big Bend bluegrass (Poa strictiramea) [1,10,29,32,45].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Juniperus flaccida
 

Photo courtesy of James Manhart, Texas A&M University

GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. An identification key is available [44].

Drooping juniper is a native small tree or large shrub that is slow growing and long-lived [42]. Height at maturity usually ranges from 25 to 30 feet (7.6-9.1 m) [37,44]. The national champion tree occurs in Juniper Canyon and is 55 feet (17 m) tall with a crown spread of 35 feet (11 m) and a circumference of 8.5 feet (2.5 m) [4]. Juniperus flaccida var. flaccida reaches a maximum height of 39 feet (12 m) [15]. The most conspicuous character of drooping juniper is its pendant branchlets [33,44]. Young drooping juniper trees usually have a narrow rounded crown. The bark is deeply furrowed and shreds into long strips [44]. The globose, berrylike cone is from 0.25 to 0.5 inch (0.63-1.3 cm) in diameter [44]. Each drooping juniper cone contains from 4 to 12 seeds (usually 6-8) that are 0.12 to 0.25 inch long [33,38,44]. The cones of J. f. var. flaccida contain from 4 to 13 (usually 6-10) seeds [15]. Drooping juniper cones collected by Adams [2] in the Chisos Mountains averaged 8.35 seeds/cone.

Toxicity: The leaves of J. f. var. flaccida and J. f. var. poblana contain volatile oils [1,3]. The composition of volatile leaf oils in both varieties is available [3].

RAUNKIAER [34] LIFE FORM:
Phanerophyte

REGENERATION PROCESSES:
Large seed crops are produced every 2 to 3 years, with light crops produced in intervening years [12]. The widespread distribution of drooping juniper in Mexico is probably partly due to the number of seeds/cone, which is "large" when compared to other junipers [48].

Pollination: Drooping juniper is pollinated by the wind.

Breeding system: Drooping juniper is dioecious [42,43,44].

Seed dispersal: Drooping juniper seeds are dispersed by birds and animals [48].

At the time of this review (2007) there is no information relating to drooping juniper seed banking, production, or germination; seedling establishment or growth; or vegetative regeneration. Research on drooping juniper reproduction is sorely needed.

SITE CHARACTERISTICS:
Drooping juniper occurs on dry, rocky or sandy, igneous soils in canyons, benches, hillsides, and ridges [12,32,33,37,38]. It preferentially grows on well-drained sites [42].

Climate: Where drooping juniper grows in the Chisos Mountains, precipitation ranges from 8.7 to 27 inches (220-680 mm), with most falling from May to October [26,45]. It rarely freezes, and summer temperatures routinely exceed 100 °F (40 °C) [26].

Elevation: In the Chisos Mountains, drooping juniper generally is found above 5,000 feet (2,000 m) [37]. In Mexico, it occurs from 4,000 to 8,000 feet (1,000-2,000 m) [3,44]. The elevational range of J. f. var. flaccida in Texas and Mexico is 3,000 to 9,500 feet (900-2,900 m) [15].

SUCCESSIONAL STATUS:
At the time of this review (2007), there is no information on the successional status of drooping juniper. Information pertaining to drooping juniper succession is much needed.

SEASONAL DEVELOPMENT:
Some researchers report that drooping juniper cones mature in September or October of their second year [37,42,44] and are persistent [42]. However, Flora of North America [15] reports a 1-year ripening period for drooping juniper.

FIRE ECOLOGY

SPECIES: Juniperus flaccida
FIRE ECOLOGY OR ADAPTATIONS:
Fire adaptations: Specific information on the fire ecology of drooping juniper is lacking. Other junipers (Juniperus spp.) are highly vulnerable to fire, and usually occur in large numbers only in fire refugia.

Fire regimes: Fire is a common occurrence where drooping juniper occurs in the Chisos Mountains. Dick-Peddie and Alberico [10] reported that lightning fires are probably highly localized, and are often confined to single trees. Downed woody fuels are usually scarce, and continuous fine fuels consist of herbs [10]. Using fire scar data, Moir [30] assessed that fire frequency in the Chisos Mountains ranged from 0.9 to 2.0 fires/century. The research conducted by Moir suggests a mean fire interval for the Chisos Mountains of approximately 70 years [29,30]. Research conducted by Leopold and Krausman [26] in the Chisos Mountains showed a mean fire interval of 60 years.

The following table provides fire-return intervals for plant communities and ecosystems where drooping juniper is important. For further information, see the FEIS review of the dominant species listed below.

Community or Ecosystem Dominant Species Fire Return Interval Range (years)
desert grasslands Bouteloua eriopoda and/or Pleuraphis mutica <35 to <100
pinyon-juniper Pinus-Juniperus spp. <35 [31]
Mexican pinyon Pinus cembroides 20-70 [30,40]
oak-juniper woodland (Southwest) Quercus-Juniperus spp. <35 to <200 [31]

POSTFIRE REGENERATION STRATEGY [39]:
Tree without adventitious bud/root crown

FIRE EFFECTS

SPECIES: Juniperus flaccida
IMMEDIATE FIRE EFFECT ON PLANT:
Specific information on the relationship of fire severity and damage to drooping juniper is lacking. Drooping juniper has shreddy bark and volatile leaf oils which probably render it highly flammable. It is probably easily killed by fire.

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
No additional information is available on this topic.

PLANT RESPONSE TO FIRE:
Information pertaining to drooping juniper's response to fire is lacking. Research on drooping juniper's response to fire is needed.

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
No additional information is available on this topic.

FIRE MANAGEMENT CONSIDERATIONS:
Information pertaining to managing drooping juniper with fire is lacking. Research is needed in all aspects of fire ecology and management of dropping juniper.

MANAGEMENT CONSIDERATIONS

SPECIES: Juniperus flaccida
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Very little is known about the importance of drooping juniper to livestock and wildlife. birds and mammals consume drooping juniper's fleshy cones [45,48]. Arizona gray foxes in the Sierra Madres of Chihuahua, Mexico, also eat the cones [23].

Palatability/nutritional value: No information is available on this topic.

Cover value: No information is available on this topic.

VALUE FOR REHABILITATION OF DISTURBED SITES:
No information is available on this topic.

OTHER USES:
Drooping juniper is planted as an ornamental outside of its native range in the United States and in southern Europe and northern Africa [37,44].

Wood Products: Drooping juniper wood is durable and is used locally for fenceposts [42,44].

OTHER MANAGEMENT CONSIDERATIONS:
Parasites: Drooping juniper is a host species to juniper mistletoe (Phoradendron juniperinum) and P. saltillense [18].

Juniperus flaccida: REFERENCES


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