Pinus muricata (bishop pine) description

Conservation Status

Pinus muricata

D.Don (1836)

Common names

Bishop, obispo, pricklecone, dwarf marine, umbrella, bull, pitch, or Santa Cruz Island pine. Older texts call it "Obispo" because it was described from near San Luis Obispo; English speakers changed that to "Bishop," the English translation of "Obispo." Since it refers to a specific place, not a generic bishop, it should be capitalized: Bishop pine.

Taxonomic notes

Type: USA, California, San Luis Obispo area, Coon Creek, 1835, T. Coulter 712 (holotype not located, isotype TCD). Synonymy: see POWO. None of the synonyms are in common use; they involve earlier efforts to subdivide the species, which are not compatible with findings from later genetic studies.

Along with Pinus attenuata and P. radiata, this is one of the "closed cone" pines, Pinus subsect. Attenuatae. All three species are serotinous pines of California and Baja California. Phylogenomics indicate that the section dates to about the Oligocene-Miocene boundary (Jin et al. 2021), a time when climates in western North America were generally getting cooler and drier; since all three species are well adapted to high-severity fire, it may have been a time of increasing fire frequency and severity. It's also thought that California's current Mediterranean climate dates to about the Miocene-Pliocene boundary (Iacobellis et al. 2016), so it's not clear how these pines spent the Miocene. Genetic studies have disagreed about which two species are sisters; they all seem to be about equally distinct.

There is an exceptionally high level of infraspecific variation in Bishop pine, which was intensively studied from 1983 to 1999, primarily through studies of morphology, needle terpenes, isozyme variation and plastome markers. The genetic studies, some of which involved large sample numbers from throughout the range of the species, find that each of the closed-cone pines is clearly distinct from its sister species but also contains significant infraspecific variation, distributed such that populations in close proximity also show high similarity (Millar et al. 1988, Hong et al. 1993, Wu et al. 1999). P. muricata occurs in a relatively small number of populations distributed along the California coast from near the Oregon border to northern Baja California. "Table 2" at right, from Millar and Critchfield (1988), summarizes the morphological and terpene differences between the populations. The northernmost trees, commonly termed the "blue strain", have glaucous foliage and are otherwise a uniform population. At Sea Ranch (latitude 31.72°) there is an abrupt transition to a green-foliage form that seems to have only recently come into contact with the northern form and is being introgressed by the glaucous form due to pollen transport by prevailing northerly winds (Millar 1983). (Note: there are also some blue strain trees south of here in an area of pygmy forest [Millar 1989].) The green strain is widespread near the Point Reyes peninsula and on the Monterey peninsula, and populations in these areas are intermediate between more northerly and southerly populations with regard to many morphological characters. South of the Monterey peninsula is a large distribution gap until the type locality, in the San Luis Obispo-Santa Barbara area; this again is a discrete population and is similar to but distinct from an offshore population in the same area occurring on Santa Cruz and Santa Rosa islands, and from the southernmost population in northern Baja California. All three of these southern groups show similar terpene composition and morphology, though the island populations are generally more similar to the Baja California trees than to the San Luis Obispo-Santa Barbara trees. An interesting variation occurs in that some trees bear exceptionally thin-scaled, symmetric cones, a character that probably warrants description as a forma and is present in most populations, but varies widely in frequency from common in the island pines to rare in the blue pines (Millar 1986a).

One very unusual feature in P. muricata is that in experimental crosses, pines from the different populations do not cross readily, and pines from the northern populations will not cross with those from the southern populations. This is the only known instance of infertility between two pine populations of the same species. Conversely, some P. muricata populations will produce fertile crosses with both P. attenuata and P. radiata (Millar and Critchfield 1988).

The blue strain trees, given their many differences from the green strain, are probably distinct at subspecific or even species rank (Millar and Critchfield 1988, Hong et al. 1993). They have not been so described. Axelrod (1980) invalidly published a var. borealis but his type specimen was from Salt Point, Sonoma Co., about 20 km south of the southernmost blue trees at Sea Ranch (this name was later validly published by Farjon [1993]; for further discussion see Millar [1986a]). Trees in the island populations having cones with smooth scales were described as P. remorata by Mason (1930), but see Millar (1986a) for a detailed discussion reducing this taxon to synonymy.

Description

Trees to 24 m tall and 90 cm dbh, with a widely varying growth form from straight to contorted and single- to multi-stemmed; crown also highly variable. Bark smooth and pale brown, darkening with age, becoming rough, and developing deep longitudinal furrows. Twigs slender to stout, orange-brown, aging darker brown, rough with persistent cataphylls. Needles two per fascicle, spreading to upcurved, persisting 2-3 years, 8-15 cm × 1.2-2 mm, stiff, slightly twisted, all surfaces with stomatal lines, margins serrate, apex abruptly acute; fascicle sheath persistent, up to 15 mm long; foliage color usually a dark yellowish green, but distinctly glaucous in populations N of latitude 31.72°. Buds ovoid-acute, dark brown, 10-15 mm long, sometimes resinous. Pollen cones ellipsoid, 15-20 mm long, pink to reddish. Seed cones maturing in 2 years, subterminal, in whorls of 1-5 on stout 5-10 mm peduncles, reflexed, serotinous, persisting for up to 70 years (or more; often old cones are enveloped by the growing branch or trunk), mostly asymmetric but often symmetrical in southern populations, lanceoloid-ovoid before opening, curved-ovoid when open, 4-9 cm long, rich glossy chestnut-brown at maturity. Cone scales with a deep red-brown distal border (the sealing band, yellow-brown on fresh cones but darkening with age) distally on adaxial surface; apophyses usually much thickened, the abaxial ones progressively more angulately dome-shaped toward base of cone; umbo central, usually bearing a stout-based, curved claw but smooth cones are common in southern populations, particularly in the island populations. Seeds obliquely ellipsoid, 6-7 mm long, dark brown to near black, with a 15-20 mm wing. 2n=24. Cotyledons 5. Seed weight 0.02 g. Wood strong, hard, with pale brown heartwood and creamy white sapwood (Millar 1986a, Perry 1991, Kral 1993, Farjon 2010, M.P. Frankis e-mail 1999.03). See García Esteban et al. (2004) for a detailed characterization of the wood anatomy.

Although P. muricata resembles the other closed-cone pines and sometimes grows with them, both P. attenuata and P. radiata have 3-needled fascicles; the 2-needled P. radiata var. binata is seldom seen and has substantially larger cones.

Distribution and Ecology

USA: California; Mexico: Baja California Norte; at 0-300(-610) m elevation (GBIF 2025). Bishop pine grows in scattered locales along the coast and offshore on Santa Cruz and Santa Rosa islands of California; where it occurs, it tends to be abundant. Climate is Mediterranean, meaning cool wet winters and warm dry summers. Climate is evidently the primary constraint on the species' distribution. On one hand there is a monotonic gradient in which precipitation diminishes, average temperatures increase, and seasonality diminishes with decreasing latitude. Overlaid on this is a strong dependence on coastal fogs and generally cooler coastal temperatures, both due to upwelling of the cold California Current just offshore. In areas where the current is far offshore, such as the Southern California Bight, there are no Bishop pines, but they appear where upwelling occurs just offshore; south of the southern range limit, the Mediterranean climate ends and the coast is evidently too warm and dry for pines (Wells 1962, Westman and Whittaker 1975, Minnich 1987, Barbour et al. 2007, Borchert and Davis 2007, Iacobellis et al. 2016, Taylor et al. 2020). Within its range, drought is one of the principal causes of Bishop pine mortality, and several such events have been recorded, with the most recent and severe occurring in 2012-2016 (Taylor et al. 2020).

Distribution data from GBIF (2025); records cleaned to minimize duplicates, cultivated specimens, mislocated specimens, and misidentified specimens. Click on any icon for more information.

Soils, slopes and substrates for Bishop pine are highly variable (Millar 1986a, Minnich 1987, Barbour and Malor 1977). Habitats include open woodlands in a mosaic with annual grassland, coastal sage scrub, and chaparral communities (Barbour and Major 1977); "pygmy" forests; and closed-canopy pure or mixed stands in coastal mountains. The most widespread formation, open coastal woodlands, can be found throughout the species' range. Trees here typically have crooked trunks, often with multiple stems and irregular crowns; in areas exposed to salt spray they may develop krummholz growth forms (photos at right). The inland forests of Marin County, where the species grows at its highest elevation and farthest from the sea, are an unusual instance of this type (Millar 1986b). "Pygmy" forests (photo at right) are a unique vegetation type largely restricted to Mendocino County. In these forests very acidic soils, mineral toxicities and deficiencies, podsolized iron hardpans, and extreme water conditions (both dry and wet) have resulted in forest communities dominated by a few stunted stress-tolerant conifers, along with a diverse community of many endemic or uncommon shrubs and herbs (Gardner and Bradshaw 1954, Millar 1989, Aitken and Libby 1994). The conifers mainly include Pinus muricata, P. contorta subsp. contorta var. bolanderi, and Hesperocyparis pygmaea, though there are also occasional stunted Abies grandis, Tsuga heterophylla and Sequoia sempervirens. Finally, closed-canopy forests (top photo at right) typically host tall, single-stemmed trees with columnar crowns, either in pure stands or mixed with species such as Abies grandis and Sequoia sempervirens in the northern range, or Pinus radiata on the Monterey peninsula (Millar 1986a, Borchert and Davis 2007, pers. obs. 2007-2025). In the Point Reyes area, closed forests tend to be dominated by P. muricata with secondary Arbutus menziesii, Umbellularia californica, Quercus agrifolia, and Notholithocarpus densiflorus (Harvey and Agne 2021); these associated species are all capable of resprouting after fire. South of the Monterey Peninsula, closed-canopy forests seem not to have been documented and are presumably absent or rare.

All these forest types are typically initiated by a stand-destroying fire, and such events typically recur at intervals of less than 100 years. This is true of all the California closed-cone pines. Studies in the Point Reyes area, which probably has the most widespread closed-canopy Bishop pine forests, have found rapid establishment of an even-aged pine cohort within 10 years post-fire; associated plants, consisting mostly of a mix of shrubs and herbs, are most diverse during this period, while most structure is legacy snags and logs from the pre-fire stand. From about 10 to 50 years post-fire the stand is dense and the trees are experiencing density-dependent mortality; understory plant diversity is at a minimum and there is little structure apart from small snags and logs. From about 50 years onward, the surviving trees attain maturity and understory plant diversity increases due to canopy gaps. Structural diversity increases, but this is associated with an increasing fuels load. Mortality from other causes, such as drought or the fungal disease pine pitch canker (Fusarium circinatum), starts to increase; but more commonly fire weather and an ignition source combine to reset the fire cycle (Harvey and Agne 2021).

Although pitch canker is a primary threat, other pests and pathogens are known to affect Bishop pine. One is the California fivespined ips, Ips paraconfusus, a bark beetle that can cause ecologically significant outbreaks in response to droughts or events such as windstorms that produce large amounts of dead wood (Schultz and Bedard 1987). Bishop pine is also a principal host for the dwarf mistletoe Arceuthobium littorum (Hawksworth and Wiens 1996). Other important pests inventoried in Bishop pine stands are listed in the table at right, from Lee et al. (2018)p

Bishop pine produces predominately serotinous cones that remain closed for several years and open after fire or on hot days. The proportion of serotinous cones varies between populations and is generally inversely proportional to latitude; the northern trees often disperse seed in the absence of fire (Duffield 1951, Millar 1986a, 1986b, Barbour 2007). Temperatures of up to 95°C do not seriously reduce seed germination, and a cone may experience temperatures as high as 400°C without exposing the seeds within to lethal temperatures (Fraver 1992). Moreover, as the cones may be retained on the trees for decades, they effectively produce a seed bank that offers the potential for rapid regeneration after a variety of disturbances, such as drought or insect attack (Bisbing et al. 2023).

Linhart (1978) has put forth the intriguing hypothesis that squirrels are an important predator on Bishop pine cones, observing that cone scales tend to be thin on the side of the cone adjacent to the branch, and also that thin-scaled cones are most abundant in the island populations, where squirrels are absent. A similar mechanism (thin scales next to the branch) has been shown to defend against squirrel predation on Pinus contorta cones (Smith 1970 and Elliott 1974 in Linhart 1978), and in P. radiata we also see thick-scaled cones on the mainland, but thin-scaled cones on the island population where squirrels are absent. Prickles and spines on pine cones are known to deter avian seed predators (Coffey et al. 1999), and the cones on the island populations of Bishop pine are largely lacking spines.

Vegetation on Santa Cruz Island was formerly severely depressed due to overgrazing by introduced domestic sheep, which were brought to the island in the 1850's; grazing remained a commercial activity until the 1930's, and thereafter a population of feral sheep persisted until the 1980s. As early as 1876 a visitor remarked that "we now have abundant signs of forests that have disappeared at the sea-level, where their stumps and roots still remain in situ. On the grounds most visited by the herds of sheep, all vegetation, save sage-brush, cactees [sic], and the erodium ... have been entirely swept away" (Rothrock 1876 in Wehtje 1994). A sheep removal project began in 1981 and by 1990 the sheep had been largely eliminated, although removal was not complete until 2011. A 1978 study had found many decadent mature pines but no pine regeneration at all, but by 1990 the the understory was filled with abundant seedlings (Wehtje 1994). The pine population was depressed by a 2012-2016 drought that was the most severe drought event on record, but once the drought ended the pine quickly responded and by 2019 there were 5 times as many seedlings observed as in 2016. Calamity struck again in 2019 with widespread mortality due to an unidentified bark beetle, but again there was abundant regeneration (Taylor et al. 2020, Tegley et al. 2020). Overall, the pattern that has emerged from ecological studies in P. muricata habitats depicts a species that is subject to frequent and often severe mortality from varied causes that include fire, drought, insects, and pathogens; but which is capable of rapid and prolific recovery from all of these disturbances. Its primary vulnerability seems to be its dependence upon the cool temperatures and summer fogs associated with the California Current, which implies a potentially acute sensitivity to climate change. However, models of climate change show very high uncertainty regarding this system, ranging from suppression of coastal upwelling to increased upwelling (Iacobellis et al. 2016).

Beside sheep, humans have introduced another threat to Bishop pine: due to its great genetic variability, it is highly vulnerable to accidental hybridization with introduced plants. In an example of this, in the 1960s seeds of unknown origin were sown in precisely the area where the blue and green races of Bishop pine are experiencing introgression. This has effectively terminated what had been an interesting natural experiment in introgression. Trees from this site are no longer fully "native" and may have impaired adaptive capabilities, such as reduced resistance to pests or to extreme weather events (Millar and Libby 1989).

The IUCN, based on a 2011 assessment, has given Pinus muricata a conservation status of "Vulnerable" due to habitat loss and fire suppression associated with development. Effects from drought are also noted, although as discussed above, the most severe drought event to date started in 2012. Potential climate change effects are uncertain, although, the Baja plants seem to be at high risk, in view of drought and heat forecast in climate change projections for southern California (Kalansky et al. 2018).

Remarkable Specimens

Since 2010, the official champion tree has been a specimen in Marin County, California. When last measured in 2018 it was 196 cm dbh and 25.0 m tall, with a crown spread of 36.0 m (Payne 2025). This also seems to be the largest tree recorded. The tallest I have seen documented was a tree near Trinidad, California that was 122 cm dbh and 51.8 tall (Metcalf 1921). This tree occurred on a site that was being logged at the time.

The oldest known living specimen, 161 years, was documented in a tree-ring chronology covering the period 1846-2008 (fully crossdated), collected at a site named "Ecological Staircase Terrace 2" on the Mendocino coast of California by Steven Voelker (doi.org/10.25921/z79b-8t53). Only one chronology has been developed for this species, and older trees likely exist.

Ethnobotany

Aboriginal use of Pinus muricata is recorded for the Pomo people, a tribe widespread in coastal California north of San Francisco Bay. They used the wood for firewood, and the roots in basketry and to make fish traps. The pitch was used as an adhesive or sealant. The seeds were both eaten fresh and dried for winter use (Native American Ethnobotany Database 2025). No medicinal uses are recorded, but decoctions from the foliage of many pine species around the world are used to treat sores and pains, and that may have been the case with Bishop pine as well.

In the modern world, the heavy, weak, knotty wood is not commercially used for timber, although in some areas trees grow straight enough to be usable. Northern blue and green provenances were tested for timber production in New Zealand in the 1970's, but proved unsatisfactory; the green trees grew slowly and were not straight in form. The blue trees performed better, especially at colder sites, but over the long term P. radiata has been a far more successful species (Shelbourne et al. 1982). Within its native range, Bishop pine continues to be used for firewood (Perry 1991 and pers. obs.). Bishop pine is rarely seen as an ornamental, even though the blue trees are fast-growing and can be quite attractive. The species is hardy to Zone 8 (cold hardiness limit between -12.1°C and -6.7°C) (Bannister and Neuner 2001).

The wood is fragrant, and its heartwood very rot-resistant. Tony Broad (email 2024.08.02) reports that "we have distilled oil from the sawdust: the yield is high (up to 40 ml per kg) and it makes a lovely perfume."

Observations

It's pretty easy to find the species in habitat. Noteworthy occurrences include:

Patrick's Point State Park and Trinidad Head, both near the northern range limit of the species in Humboldt County, California.
Jug Handle State Natural Reserve. The parking area is 3.7 miles S of the Noyo River bridge in Fort Bragg. A walk seaward from the parking area will show you some amazing large krummholz trees (photos at right) and some small contorted krummholz even closer to the high winds and salt air. Walking the trail inland will take you through a diverse forest that features P. muricata, P. radiata (not native, but introduced by early settlers), Tsuga heterophylla and Abies grandis (both near their southern range limits), Sequoia sempervirens, and at the end a pygmy forest dominated by P. muricata, P. contorta var. bolanderi, and Hesperocyparis pygmaea. All in all, it's one of the most edifying conifer walks in California. The Fort Bragg area also has many more fine examples of the "blue" trees; a good coastal example is at the Noyo Headlands Park just north of the Noyo River Bridge.
Point Reyes National Seashore is home to the most extensive of the northern "green" stands, most of which are located along Inverness Ridge. At various locations there are woodlands of wind-formed trees, as well as dense forests of tall straight trees. Harvey and Agne 2021 provide a good review of the diversity of Bishop Pine forests at this site; also see the Peattie quote below.
On the Monterey Peninsula, the S.F.B. Morse Botanical Reserve is crossed by a good network of day-hiking trails and is another fine example of pygmy forest, with lots of P. muricata, P. radiata, and Hesperocyparis goveniana. This is the best place to see Bishop and Monterey pine growing together.
In the San Luis Obispo area, the species is best seen from the Point Buchon trailhead at Montaña de Oro State Park. Somewhere up Coon Creek from here, the Irish plant-hunter Thomas Coulter collected the type specimen in 1835.
The species is quite common in Channel Islands National Park on Santa Cruz and Santa Rosa islands. If you go, note that the island subspecies of Torrey pine, P. torreyana subsp. insularis, is endemic to Santa Rosa Island—so you may prefer to visit Santa Rosa rather than Santa Cruz.
I don't have a specific location for the Baja trees, but note that most of the recorded observations in the area are along the road from San Vicente to the beach.

Remarks

The species was discovered in 1835 by a young Irish botanist named Thomas Coulter, memorialized by another species he collected that year, Pinus coulteri. He collected it near Mission San Luis Obispo, thus the name "Bishop" pine (Little 1980). It was published by D. Don the following year in the Transactions of the Linnaean Society with the epithet muricata. The closest Latin word is muricatim, which means "shaped like a purple snail"; this is a reference to the mollusc family Muricidae, some members of which have very spiky, conical shells; thus the epithet compares the cones of P. muricata to the shells of the Muricidae (Tony Broad, email 2024.08.02).

If you want an easy way to open the serotinous cones, simply drop them in boiling water for about 10 seconds and then let them dry at room temperature. To germinate the seeds, soak them overnight in cold water and then plant them, keeping them at room temperature (Millar 1983).

"The true beauty of Bishop Pine is seen on the east or leeward side of Inverness Ridge, and at near-by Shell Beach, where the trees overhang Tomales Bay. Here, sheltered from the full force of the eternal sea winds, but with the hoarse voice of the surf, ... the Bishop Pine forms lovely groves, with picturesquely twisted stems, and flat-topped or dome-shaped crowns that interlock, tree with tree. So each tree takes protection from its brethren and all together they achieve an air of inviolable serenity and a sort of pagan sanctity. " —Donald Peattie, A Natural History of Western Trees.

Citations

Aitken, S. N., and W. J. Libby. 1994. Evolution of the pygmy-forest edaphic subspecies of Pinus contorta across an ecological staircase. Evolution 48:1009–1019.

Axelrod, D. I. 1980. History of the maritime closed-cone pines, Alta and Baja California. Berkeley: University of California Press.

Barbour, M. G. 2007. Closed-cone pine and cypress forests. Pages 296–312 in M. G. Barbour, T. Keeler-Wolf, and A. A. Schoenherr, editors. Terrestrial Vegetation of California, 3rd Edition. University of California Press.

Barbour, Michael G. and Jack Major (eds.). 1977. Terrestrial Vegetation of California. New York: John Wiley & Sons.

Barbour, Michael G. and Jack Malor, eds. 1977. Terrestrial vegetation of California. New York: John Wiley and Sons.

Barbour, M. G., T. Keeler-Wolf, and A. A. Schoenherr (eds.). 2007. Terrestrial Vegetation of California, 3rd Edition. Berkeley, CA: University of California Press.

Bisbing, S. M., A. K. Urza, R. A. York, L. E. Hankin, and T. R. Putz. 2023. Persistent, viable seedbank buffers serotinous bishop pine over a broad fire return interval. Fire Ecology 19:35. https://doi.org/10.1186/s42408-023-00194-3.

Borchert, M. I., and F. W. Davis. 2007. Central Coast Bioregion. Pages 321–349 in N. Sugihara, editor. Fire in California’s Ecosystems. University of California Press.

Coffey, K., C. W. Benkman, and B. G. Milligan. 1999. The adaptive significance of spines on pine cones. Ecology 80:1221–1229.

Don, D. 1836. Descriptions of five new species of the genus Pinus discovered by Dr. Coulter in California. Trans. Linn. Soc. London 17:439-444. Available at the Biodiversity Heritage Library, accessed 2022.12.23.

Duffield, ]. W. 1951. Interrelationships of the California closed-cone pines with special reference to Pinus muricata D. Don. Ph.D. Dissertation, University of California, Berkeley.

Elliott, P. F. 1974. Evolutionary responses of plants to seed-eaters: pine squirrel predation on lodgepole pine. Evolution 28:221-231.

Farjon, Aljos. 1993. Regnum Vegetabile 128:136.

Fraver, S. 1992 The insulating value of serotinous cones in protecting pitch pine (Pinus rigida) seeds from high temperatures. Journal of the Pennsylvania Academy of Science 65:112–116.

Gardner, R. A. and K. E. Bradshaw. 1954. Characteristics and vegetation relationships of some podzolic soils near the coast of northern California. Soil Science Society of America Journal 18(3):320-325.

GBIF [Global Biodiversity Information Facility]. 2025. Occurrrence download "Pinus muricata", https://www.gbif.org/occurrence/download/0023882-251025141854904, 2025.11.10.

Harvey, B. J., and M. C. Agne. 2021. Bishop pine (Pinus muricata) forest health. White paper prepared for the Golden Gate Parks Conservancy. https://depts.washington.edu/bjhlab/wordpress/wp-content/uploads/2022/02/PIMU_PORE_WhitePaper_Final_20210626.pdf, accessed 2025.11.17.

Hong, Y.-P., V. D. Hipkins, and S. H. Strauss. 1993. Chloroplast DNA diversity among trees, populations and species in the California closed-cone pines (Pinus radiata, Pinus muricata and Pinus attenuata). Genetics 135:1187–1196.

Iacobellis, S. F., D. R. Cayan, J. T. Abatzoglou, and H. Mooney. 2016. Climate. Ch. 2 in Mooney, Harold, and Erika Zavaleta (eds.). Ecosystems of California. Berkeley: University of California Press.

Jin, Wei-Tao, David S. Gernandt, Christian Wehenkel, Xiao-Mei Xia, Xiao-Xin Wei, and Xiao-Quan Wang. 2021. Phylogenomic and ecological analyses reveal the spatiotemporal evolution of global pines. Proceedings of the National Academy of Sciences 118(20): e2022302118. doi.org/10.1073/pnas.2022302118.

Kalansky, J., D. Cayan, K. Barba, L. Walsh, K. Brouwer, and D. Boudreau. 2018. California’s Fourth Climate Change Assessment. https://www.climateassessment.ca.gov/, accessed 2025.11.17.

Lee, Christopher A., Steve Voelker, and Peter A. Angwin. 2018. Investigating causes of bishop pine decline on California's north coast. Pp. 145-156 in Potter, K. M. and B. L. Conkling, eds. Forest health monitoring: national status, trends, and analysis. GTR SRS-239. Asheville, NC: USDA Forest Service, Southern Research Station.

Linhart, Y. B. 1978. Maintenance of variation in cone morphology in California closed-cone pines: the roles of fire, squirrels and seed output. The Southwestern Naturalist 23:29-40.

Mason, H. L. 1930. The Santa Cruz Island pine. Madroño 2:8-10. Available: Biodiversity Heritage Library, accessed 2025.11.16.

Metcalf, Woodbridge. 1921. Notes on the Bishop pine (Pinus muricata). Journal of Forestry 19:886-902. Available: Biodiversity Heritage Library, accessed 2023.11.12.

Millar, C. I. 1983. A steep cline in Pinus muricata. Evolution 37:311-319.

Millar, C. I. 1986a. The Californian closed cone pines (subsection Oocarpae Little and Critchfield): A taxonomic history and review. Taxon 35:657-670.

Millar, C. I. 1986b. Bishop pine (Pinus muricata) of inland Marin County, California. Madroño 33(2):123-129.

Millar, C. I. 1989. Allozyme variation of bishop pine associated with pygmy-forest soils in northern California. Canadian Journal of Forest Research 19:870–879.

Millar, C. I. and W. B. Critchfield. 1988. Crossability and relationships of Bishop Pine. Madroño 35:39-53. Available: Biodiversity Heritage Library, accessed 2025.11.16.

Millar, C. I. and W. J. Libby. 1989. Restoration: Disneyland or a native ecosystem? Ecological Restoration 7:2–10.

Millar, C. I., S. H. Strauss, M. T. Conkle and R. D. Westfall. 1988. Allozyme differentiation and biosystematics of the Californian closed-cone pines. Systematic Botany 13: 351-370.

Minnich, R. A. 1987. The distribution of forest trees in northern Baja California, Mexico. Madroño 34:98–127.

Native American Ethnobotany Database. 2025. Results of search for the named species of Pinus. Available: http://naeb.brit.org/, accessed 2025.11.17.

Payne, J. (ed.). 2025. The 2024 Register of National Champion Trees. National Champion Tree Program, https://nationalchampiontree.org/.

Perry, Jesse P. 1991. The Pines of Mexico and Central America. Portland, OR: Timber Press. 231 pp.

Rothrock, J. T. 1876. Report upon the operations of a special natural-history party and main field-party no. 1, California section, field season of 1875. Appendix H5, pp. 202-203. In: Annual report upon the geographical surveys west of the one hundredth meridian, Appendix JJ (edited by G. M. Wheeler), Government Printing Office, Washington, D.C. Available: Google Books, accessed 2025.11.17.

Sargent, C. S. 1897. The silva of North America: a description of the trees which grow naturally in North America exclusive of Mexico. Vol. XI. Houghton, Mifflin and company, Boston, New York.

Schultz, D. E., and W. D. Bedard. 1987. California Fivespined Ips. 8 pp. Forest Insect and Disease Leaflet, USDA Forest Service, Washington, DC.

Shelbourne, C. J. A., M. H. Bannister, and M. D. Wilcox. 1982. Early results of provenance studies on Pinus muricata in New Zealand. New Zealand Journal of Botany 27(1):50-66.

Smith, C. C. 1970. The coevolutiion of pine squirrels (Tamiasciurus) and conifers. Ecological Monographs 40:350-371.

Taylor, A., T. Biswas, J. M. Randall, K. Klausmeyer, and B. Cohen. 2020. Parched pines: a quantitative comparison of two multi-year droughts and associated mass mortalities of bishop pine (Pinus muricata) on Santa Cruz Island, California. Remote Sensing in Ecology and Conservation 6:20–34.

Tegley, A., E. Schwarz, V. Joyce, and G. Hassinger. 2020. 2019-20 Baseline Demographic Survey of the Bishop Pine (Pinus muricata) on Santa Rosa Island, California.

Wehtje, W. 1994. Response of a bishop pine (Pinus muricata) population to removal of feral sheep on Santa Cruz Island, California. Pages 331-340 in: W. Halvorson and G. Maender (eds.), The fourth California Islands symposium: update on the status of resources. Santa Barbara Museum of Natural History, Santa Barbara, CA.

Wells, Philip V. 1962. Vegetation in relation to geological substratum and fire in the San Luis Obispo Quadrangle, California. Ecological Monographs 32(1):79-103.

Westman, W. E. and R. H. Whittaker. 1975. The pygmy forest region of northern California: studies on biomass and primary productivity. Journal of Ecology 63:493-520.

Wu, J., K. V. Krutovskii, and S. H. Strauss. 1999. Nuclear DNA diversity, population differentiation, and phylogenetic relationships in the California closed-cone pines based on RAPD and allozyme markers. Genome 42:893–908.

This page co-edited with M.P. Frankis, 1999.03.