Hesperocyparis guadalupensis

Guadalupe cypress is a coniferous evergreen tree with a dome-shaped and broad crown when fully mature. The species is variable in size, with mature trees reaching tall, though they are noted as being towards the lower end of this range in their native habitat in the 2000s. The first scientific description recorded them as growing to "40 feet high or more". The foliage grows in dense sprays, dark blue-green or glaucous blue in color. The leaves are scale-like, 1.5–2 millimeters long, in four rows on rounded (not flattened) shoots. The seed cones are nearly spherical, with eight to ten horn-shaped scales, narrow at the base and wide at the top, with a pointed tip. Each seed is about 5–6 millimeters long with a small wing structure about 1 millimeter. The lifespan of cypress trees can be estimated from the number of annual growth rings found in the trunks of dead trees. Using this measurement, the average longevity is estimated at 150 to 160 years for a tree with a 50 centimeter diameter, The seedlings are very similar to all other western cypress species, with three to five long, thin, needle-like seed leaves that start out upright and then spread outwards from the stem. Each leaf is usually between 8 and 12 millimeters long. The juvenile leaves also resemble the needle-like seed leaves, but are not quite as long or as thick or fleshy in texture. In the second to fourth year of life the young tree will start to produce adult foliage rather than another set of juvenile leaves. In the first year of growth, given favorable growing conditions, young trees will reach an average of 40 to 45 centimeters in height. By the end of a second year they will reach 110 centimeters. This rapid growth can continue, with a new tree reaching an estimated 9.7 meters in its first decade. ==Taxonomy==

Specimens of Hesperocyparis guadalupensis were collected by Edward Palmer in 1875 during a botanical collecting trip to Guadalupe Island. In 1896 Maxwell T. Masters, as part of a paper on the genus Cupressus as a whole, thought it properly classified as Cupressus macrocarpa var. guadalupensis, reducing it to a botanical variety. Though Masters was followed in full or at least in part in these combinations, other botanists continued to regard the species as correctly identified under the name C. guadalupensis. By 1970, botanical opinions had so far reversed that Elbert Luther Little published a paper in which he combined the species Cupressus forbesii with C. guadalupensis as variety forbesii. In the 2000s, studies of the genetics of these species have indicated that they are separate species, though confirming they are closely related. Though an isolated island population, Guadalupe cypress has greater genetic diversity than its mainland relatives. This lack of a population bottleneck suggests that prior to recent disturbances it had a large and stable population. There was a second proposed reclassification to a new genus Neocupressus in the same year, but the classification as Hesperocyparis has been given priority. and in the Gymnosperm Database. Similarly, in Spanish it is commonly called "Ciprès de Guadalupe" and is listed on a Mexican government website as "Cedro de la isla Guadalupe ". Another, less common, name used for the species in California is "blue cypress" for the color of its foliage, ==Distribution and habitat==

The Guadalupe cypress, Hesperocyparis guadalupensis, is endemic to Mexico, only found naturally on Guadalupe Island in the Pacific Ocean west of Baja California. It is found growing at altitudes of . The estimated population of the tree prior to the introduction of goats to the island was about 75,000. In 1885 the botanist Edward Lee Greene observed that while there was evidence of an extensive cypress forest on the northern side of the island, only dead and fallen trees remained there. There was also a smaller grove on the east side of the island, but it too disappeared sometime after the 1920s. In addition the available evidence indicates that the frequency of fire has increased on the island. Though Guadalupe cypress is partially adapted to fire, the increasing number of fires is likely to be an additional cause of early mortality for the trees. ==Ecology==

Together with the Guadalupe palm (Brahea edulis) and the Guadalupe pine (Pinus radiata var. binata), Guadalupe cypress is one of the dominant defining species of plant on the island, a keystone in its natural ecology. ==Conservation and restoration==

Guadalupe Island had a population of numerous, but old, trees in 2000. Estimates of the remaining population vary widely. In the year 2000 it was estimated to be 4,000 individuals. However, the IUCN gives an undated estimate of only 200 mature trees remaining. In order to accomplish this task Grupo de Ecología y Conservación de Islas, A.C. (GECI) used 40 sterilized Judas goats to track down the last holdouts hiding in less accessible areas of the island like canyons, cliffs, and caves. Soon after the eradication the population was estimated to be 14,700 in 2005, though without any information on if this included new seedlings. An assessment conducted one year later found 120,000 new trees in the southern patch. A 2019 assessment found over 67,000 trees over 2 meters in height. In addition to the natural regeneration, the Mexican foundation GECI has partnered with the Fondation Franklinia, a Swiss charity, to plant thousands of seedlings of the cypress and two other endangered tree species on the island since 2020. They have also sponsored work to reduce the fuel load of the landscape to reduce future threats from fire. The presently recovering populations are still vulnerable and long-term viability is not assured. It appears this cypress is more vulnerable to drought than other native plants on the island, such as the Guadalupe variety of Monterey Pine (Pinus radiata var. binata), and so the population could decline further with future climate change. Hesperocyparis guadalupensis is considered an endangered species by the IUCN. It is also designated as an endangered species by the government of Mexico. ==Cultivation==

Though endangered in the wild, Guadalupe cypresses have long been cultivated in California and in other parts of the world. They are also particularly suited to coastal plantings, being resistant to damage by coastal sprays and winds. They are also very adaptable to different soil conditions. Unlike the Monterey cypress they are highly resistant to cypress canker, with only one report of a tree being infected in scientific literature. In Europe they sometimes show signs of cypress bark beetles (Phloeosinus) in their crown. There are not any significant plantations of Guadalupe cypresses and they are not used to any extent in their native habitat. ==References==