Pinus radiata var. radiata

Pinaceae

Endemic to central-coastal California, USA where the three remaining stands are mainly threatened by fire, pitch canker and urbanisation.

Distribution

Native stands of the type variety of Monterey Pine are found in three distinct areas of central-coastal California in San Mateo, Santa Cruz, Monterey, and San Luis Obispo Counties. The northernmost stand is east of Point Año Nuevo, the central stand 48km to the south near Monterey and Carmel, and the southernmost stand about 105km away in the Pico Creek-Cambria area. The north-south range is about 209 km.

Habitat and Ecology

Monterey Pine is part of the coastal closed-cone coniferous woodland. This habitat is strongly influenced by its proximity to the Pacific Ocean from which the cold waters of southward-flowing currents result in high humidity, low temperatures, and summer fogs. The pine is seldom found more than 11km from the sea.

Fire is a major influence affecting the extent and makeup of Monterey Pine stands. Fire is frequent, sometimes of natural causes, often accidental, and sometimes deliberately set. Graziers at Cambria, for example, burned the woods to obtain more grass. At Año Nuevo, frequent fires have helped to maintain the pine forest. Without fire, the taller and longer-lived coast Douglas-fir (Pseudotsuga menziesii var. menziesii) would usurp land occupied by pines. Much regeneration and a number of even-aged stands at all three main locations can be traced directly to the influence of fire.

Human Uses

Monterey pine is the most widely planted tree species in the world. Its tiny natural relict stands fall into insignificance to the millions of hectares planted in Australia, New Zealand, Chile, Argentina, Uruguay, South Africa, Kenya, and Spain. Provenance is almost exclusively from mainland California. Its spectacularly rapid growth under plantation conditions is the main reason for its success in commercial forestry and for many of the above mentioned countries it is the most important timber tree. The wood is rather brittle and coarse grained and most suitable for pulp wood, but in many countries where it has been introduced it is also put to other uses e.g. construction, carpentry and joinery, veneers, furniture, laminated wood, and crates and boxes. This species has been widely planted as a landscape tree in urban areas, parks and large gardens, where it can grow to huge size in relatively short time. It is a very suitable tree to form a living screen against wind and traffic noise and tolerates relatively high levels of air pollution

Conservation Status

Global status and rationale

Critically Endangered B2ab(ii,iii)

The main concern is with the small original subpopulations, which have been severely reduced in the past but are now threatened by other tree species encroaching, while at the same time the taxon is spreading spontaneously from planted trees, often of unknown provenance as to the three subpopulations. The distinction between ‘original’ trees belonging to these subpopulations, and other trees in their vicinity is already blurred in several places. This ultimately amounts to a case not of species conservation (or the var. radiata) but the preservation of genotypes. The introduction of an alien pathogen that severely affects the original sub-populations has caused further dieback and continues to pose a serious threat.

Global threats

The total area of occupancy (AOO) of Pinus radiata var. radiata has been reduced to about 50% of the ca. 10,000ha estimated to have been covered by it on the arrival of Europeans in California. The current main, but still minor threat to this variety is forest succession, particularly in the southernmost population. Pinus radiata var. radiata has extended it range there in recent decades, but succession to a forest type that eventually excludes this pine is also taking place in the absence of fire. Urbanisation interferes with the natural fire cycles which favour regeneration of P. radiata var. radiata. The (genetic) distinction between natural and semi-natural occurrence is also blurred by plantings in this and other areas. The accidental introduction of pitch canker (Fusarium circinatum [anamorph] Ascomycetes) poses another recent threat. The three remaining native stands of var. radiata are infected and under threat of extinction from this disease, introduced to California in 1986. When trees begin to die of the disease, they attract bark beetles which provide a pathway for infection of other trees. In some stands, 80–90% of trees are infected

Conservation Actions

All three subpopulations are now legally protected. They occur partly in protected areas.