Cupressaceae

Cupressus arizonica var. stephensonii (C.B.Wolf) Little

Endemic to the US-Mexican border where fire is a major threat

Distribution

Known from just from two localities on either side of the US-Mexican border. One consisting of a few scattered trees near the headwaters of King Creek on the southwest side of Cuyamaca Peak, San Diego County, the other 2 km NE of El Rincón in Arroyo Seco.

Approximately 1000 individuals existed in the Cuyamaca Peak subpopulation before the 2003 fires. More trees than this are likely to have existed before the Conejo fire of 1950 which already extirpated part of the population. Most of the remaining subpopulation was burnt in the October 2003 Cedar Fire, though (as expected for a fire-climax species) subsequent regeneration has been good. Fires have also occurred in the Mexican subpopulation, but to what extent these were destructive is not recorded.

Habitat and Ecology

In chaparral leading up to Pinyon-Juniper woodland and oak woodland, with Pinus coulteri, Juniperus californica, Quercus spp., Adenostoma fasciculatum, Arctostaphylos glandulosa, Ceanotus spp., Cercocarpus spp., Rhamnus spp., on dry slopes and ridges above creek beds. It is the only California Cypress to release pollen in the summertime.

Conservation Status

Global status

Critically Endangered B2ab(iii)c(ii,iv); C2b

Global rationale

There are two subpopulations, one in Alta California (USA) and one in Baja California (Mexico). The one in the USA has experienced two devastating fires since 1950, reducing the number of mature trees by 90% or more. The other subpopulation in Mexico has also been subject to fires, but no population numbers are known. Regeneration is occurring after fire, but it is slow and when fires become more frequent, may not be successful without careful management. This management is now undertaken in the USA but, as far as we know, not (yet) in Mexico. This variety meets two criteria for Critically Endangered.

Global threats

The previous IUCN Red List assessment occurred in 1998, before the USA subpopulation of this taxon was reduced to thirty or forty individual trees by the 2003 Cedar Fire. This remnant subpopulation is now under active management but numbers are so low that the population could be wiped out very easily by fires, invasive pests or fungus attack. Because the surrounding forests are managed the species may also be threatened by fire suppression which could lead to a lack of reproduction and a build up of resin which will cause very hot fires, if started, which the species will not be able to cope with. The situation with the other subpopulation in Mexico is less well known but there is unlikely to be active management at present.

Conservation Actions

Species management guidelines are adopted in Cleveland National Forest.

References and further reading

  1. Adams, R.P., Bartel, J.A. & Price, R.A.. (2009). A new genus, Hesperocyparis, for the cypresses of the western hemisphere. Phytologia 91(1):160-185.
  2. de Laubenfels, D.J. (2009). Nomenclatural actions for the New World cypresses (Cupressaceae). Novon 19(3):300-306.
  3. Farjon, A. (2005). A Monograph of Cupressaceae and Sciadopitys. Royal Botanic Gardens, Kew.
  4. Farjon, A. (2013). Cupressus arizonica var. stephensonii. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. . Downloaded on 05 July 2013.
  5. Griffin, J.R. & Critchfield, W.B. (1972). The distribution of forest trees in California. USDA Forest Service, Research Paper PSW-82 (reprinted with supplement, 1976). Pacific Southwest Forest and Range Experiment Station, Berkeley, CA.
  6. Little, D.P. (2006). Evolution and circumscription of the true cypresses (Cupressaceae: Cupressus). Systematic Botany 31(3): 461-480.

External links

Entry information:

Entry author:

A.Farjon ·

Entry last edited:

30 Oct 2019

Recommended Citation:

A.Farjon, 2019, Cupressus arizonica var. stephensonii, from the website: ‘Threatened Conifers of The World’ (https://threatenedconifers.rbge.org.uk/conifers/cupressus-arizonica-var.-stephensonii). Downloaded on 22 May 2024.

Categorised in:

Critically Endangered, Cupressaceae and Northern Mexico / SW USA