Pinus pinaster (maritime pine)

P. pinaster is regarded as highly invasive and its past and future behaviour have been modelled in regions where it is a serious problem. Prolific seed production, wind-dispersed seed and rapid growth rate all contribute to its ability to invade native habitats, which suffer a consequent reduction in species diversity. P. pinaster is reported to be an aggressive colonizer in Chile, Uruguay, Australia, New Zealand and South Africa. Binggeli (1999) regarded this as a highly invasive plant, while Rejmánek (1995) rated it as one of the five most invasive pines. Richardson et al. (1994) considered P. pinaster to be the most widespread invasive pine in South Africa, with much of the spread occurring on endangered fynbos vegetation.

P. pinaster shows considerable variation over its natural range, leading to several attempts at division into subspecies, varieties and races, according mainly to provenance, morphological characteristics of the trunk and branching, tolerance to calcareous substrates, and frost resistance. The observed variation may be categorized into two main groups, now often considered as subspecies: the Atlantic group (P. pinaster subsp. atlantica) comprising provenances from Portugal, northwestern Spain (Galicia) and southwestern France (the Landes); and the Mediterranean group (P. pinaster subsp. pinaster) comprising provenances from inland Spain, Morocco and the Mediterranean basin. Some authors consider the latter to be a separate species, Pinus mesogeensis Fieschi & Gaussen, but this classification has not obtained general acceptance. The recognized common name for P. pinaster is maritime pine.

P. pinaster is a relatively large tree, 20-40 m tall, with an average diameter at breast height (dbh) at maturity of 35-40 cm. Crowns of old trees are wide and flat and the bole is clear over most of its length. Plantation trees have long, clean cylindrical stems in contrast to those of open-grown individual trees where trunks are broad at the base with a pronounced taper and increased branching. It has a deep tap root with secondary roots well-developed. The bark is thick, deeply fissured and dark red-brown. Needles are spiny, stout, stiff but not rigid, frequently twisted, occurring in pairs, with a vivid green colour. Flowers appear between late winter and mid-spring; male flowers usually abundant, clustered in shallow rings beneath the leaves with pollen shed in early spring. Female flowers occur on the tips of expanding shoots and are dull red in colour. Cones are nearly sessile, very oblique at the base, slightly curved ovoid-conic; shiny light-brown with scales and a broad transverse ridge rising to a central, small, upcurved prickle. Cones ripen between late summer and autumn, persisting closed on the tree for several years.

There is some controversy about the area of origin of P. pinaster, although the centre of natural distribution appears to be western Mediterranean regions including southern France, Corsica, Sardinia, Italy, Spain and Morocco (subsp. pinaster), as well as more western regions, centred around coastal Atlantic areas of France, Spain and Portugal (subsp. atlantica). Lacking further information, Algeria and Tunisia and other parts of Europe are treated as an introduced range in this datasheet.

The range of P. pinaster has been much extended by cultivation, and it is widely planted in the Landes and Atlantic coastal regions of France, as well as throughout the Mediterranean region for timber and resin production, dune conservation and very often for pulp production. It was introduced into the UK in the 1600s (Mitchell, 1974), and has been extensively planted in Europe outside its natural distribution area, e.g., in Belgium, Turkey, Greece and countries of the former Yugoslavia (subsp. pinaster). It was introduced into New Zealand in the 1830s (Knowles and Miller, 1989), as well as South Africa and Australia (subsp. atlantica) and numerous other countries with a Mediterranean climate, such as parts of Chile, Argentina, Uruguay and the USA.

P. pinaster has become invasive in areas where it has been used extensively for forestry, notably South Africa, New Zealand and Hawaii, USA. Biological characteristics such as high reproduction capacity, air borne seed and rapid growth rate contribute to the risk of invasion following its intentional introduction. Sites of other introductions should be monitored for signs of invasive behaviour. It is a category 2 invader under the Conservation of Agricultural Resources Act, 1983 in South Africa (Henderson, 2001).

P. pinaster seeds are generally dispersed by the wind. Dean et al. (1986) also report that baboons may disperse P. pinaster seeds in South Africa. Long-distance dispersal was intentional, as this species was deliberately introduced to South Africa as a timber tree (Cronk and Fuller, 1995) and to other countries for a variety of uses.

The habitat in the native range of P. pinaster is typically on sands or poor soil in coastal regions (Weber, 2003). Henderson (2001) reports the invasion of both montane and lowland fynbos in South Africa where this species is an alien invader. In other areas of the world where it has become invasive, P. pinaster is known to colonize coastal dune areas (Uruguay), along road verges, in Banksia and Eucalyptus marginata woodlands (Australia), grassland slopes, cliff faces, cut-over forests, scrub and shrublands (New Zealand), fynbos (South Africa) and disturbed sites (Chile).

Genetics

P. pinaster shows a high degree of genetic variation over its native range. Some authors recognize as many as five different races corresponding to several geographical locations in Western Europe, the Mediterranean region and North Africa. Most of that variation has some kind of expression in growth characteristics, stem straightness and taper, fine branching and frost resistance. A high degree of heritability was evident, particularly for stem form, as well as for the chemical characteristics of resin monoterpenes. Provenances from Portugal, northwestern Spain and southwestern France (P. pinaster subsp. atlantica) exhibited faster growth than those from the Mediterranean, inland Spain or Morocco (mainly P. pinaster subsp. pinaster). However, some provenances of the latter group have a remarkably straight stem (e.g., the Corsican race), or a notable adaptation to summer drought and limestone substrates regardless of their lack of vigour (e.g., the Moroccan race from Tamjout), as compared to provenances of the former group. A Portuguese provenance from Leiria (central coastal Portugal) was genetically improved in Western Australia, South Africa and Portugal, allowing a growth gain estimated to be 20%, as well as an improvement of about 40% for stem form.

Physiology and Phenology

P. pinaster is fast-growing until it reaches an age of 60 years old, when annual growth rate usually decline. Flowers appear between late winter and mid-spring, and cones ripen between late summer and autumn, persisting closed on the tree for several years.

Reproductive Biology

This species has monoecious flowers (Cronk and Fuller, 1995). It is difficult to establish the age from which P. pinaster starts to produce fertile seeds because this factor varies with geographic location. In general, however, flowering may begin at about 6 years old, but regular seed production commences only at 10-15 years of age. Large quantities of seed are produced (Cronk and Fuller, 1995). The cones are serotinous meaning that they are able to withstand the fire that may kill the parent tree, and be stimulated to subsequently release the seeds (Macdonald and Richardson, 1986). According to Dean et al. (1986) the duration of seed viability is approximately one year.

Environmental Requirements

P. pinaster tolerates different climate conditions depending on the subspecies. In general, it occurs naturally in warm temperate regions including the Mediterranean area, with an oceanic influence on climate, mainly in humid and sub-humid areas, where annual rainfall is greater than 600 mm. In spite of that, it is possible for trees to survive in areas with only 400 mm annual precipitation, providing that there is sufficient atmospheric moisture. In particular, the southern provenances (P. pinaster subsp. pinaster) may grow well in semi-arid conditions. However, it will grow best in areas with a mean annual precipitation of 850 mm, with at least 75 mm in the period between May and September. In its native range it only withstands a maximum of 100 consecutive days without rainfall, but when used in plantations in some areas it can tolerate a maximum of 150 days of drought. Maritime pine cannot tolerate shade, and grows best at low and medium altitudes.

P. pinaster may be found in both flat and mountainous sites in its native range, but usually at low to moderate altitudes. The subspecies atlantica is less tolerant of high altitude than the subspecies pinaster. It seems to prefer siliceous soils with a coarse texture, especially sandy soils, but it can tolerate other soil types. The subspecies pinaster can tolerate some calcareous soils, especially when they have a coarse texture and are free-draining, whereas subsp. atlantica, however, has a low tolerance to limestone soils, and exhibits a clear preference for sandy silicate soils, and has played an important role in the afforestation of loose sand dunes along the western coast of the Iberian Peninsula especially in northern and central Portugal. It has adapted well to a substrate of silicate origin with low aggregation, poor in major nutrients and organic matter. Afforestation of these areas was undertaken during the late 1800s and first half of the 1900s, and played a major role in dune consolidation and soil improvement. Similarly, the Landes region of southwestern France, with sandy soils, has been extensively planted with P. pinaster. In South Africa, a study of four invasive pines found that soil pH was the most important predictor for the distribution of isolated trees, whereas the establishment of dense pine stands was largely determined by fire history (Rouget et al., 2001).

Insect pests

Cones and seeds

Damage to cones and seeds are minor in heavy cone crop years; however, in the years following a heavy cone crop, the entire cone crop may be lost, as a large insect pest population is concentrated to a much reduced food supply. Because of this, the greatest impact of cone and seed pests is found in seed production orchards. Pissodes validirostris (the pine cone weevil) is a coleopteran (Curculionidae) and Dioryctria mendacella (the cone worm) is a lepidopteran (Pyralidae). After an attack by these insects, it is advisable to collect infested cones from the site and burn them in order to prevent the completion of the pests' life cycle.

Insects feeding on buds, shoots and twigs

These pests may cause substantial long-term damage, affecting plant growth and wood quality; they may also weaken the tree, facilitating attack by other organisms. They are particularly important in young plantations. Serious infestations seem to be associated with particular site and stand conditions that affect the vigour and exposure of seedlings and saplings. Outbreaks of shoot moths frequently occur in stands growing in dry or poorly drained sites, or in sites that have suffered soil compaction, erosion or nutrient deficiencies. Moreover, tip and shoot insect pests often prefer open conditions, which means that damage is most intense in sparsely stocked clear-cut areas and plantations. In conclusion, it is important that the manager use care in selecting planting sites and stocking densities, as well as avoiding damage to the site during harvesting operations.

Rhyacionia buoliana (the pine shoot moth) is a Lepidoptera of the Tortricidae family. It is controlled with the use of growth inhibitors (diflubenzuron) in the spring (before the larvae penetrate the buds), by sexual pheromone trapping systems (to lure males) and by biological control (Adalia bipunctata is a predator of the this species). When infested, a site should be pruned and all the attacked woody material burned. If the infestation is in a nursery, all plants must be uprooted and destroyed.

Defoliators

Leaf-feeding insects attack forest trees of all ages, but outbreaks are often associated with older stands, overstocked stands, or stands growing on poor sites. The immediate effect of defoliation is a reduction in the vigour and growth of the tree. Reduction in growth may have a significant economic impact on timber production when large areas are affected. Defoliation sometimes results in considerable tree mortality, particularly when the forest has been subjected to other stress factors such as nutrient or water deficiencies, extreme competition, or old age. In addition, the weakened trees often become susceptible to tree-killing insects, such as bark beetles, which frequently cause extensive mortality following defoliator outbreaks. Thaumetopoea pityocampa (the pine processionary moth) is a Lepidoptera of the Thaumetopoeidae family and it is the most serious pest of P. pinaster in the Mediterranean region. It can be controlled chemically with insect growth inhibitors (diflubenzuron, hexaflumuron, triflumuron) and by biological control (Bacillus thuringiensis). Neodiprion sertifer (Hymenoptera, Diprionidae) can be controlled by use of a feeding inhibitor (ketopodocarpenoic acid) sprayed on the foliage and by biological control (Bacillus thuringiensis).

Stem feeders

A number of insect groups feed on or within the stems of forest trees but, of these, the bark beetles (Scolytidae) are by far the most destructive. Bark beetle adults bore into the bark of living or recently killed trees and lay their eggs in galleries constructed in the cambial region. At the same time, bark beetles may introduce pathogenic fungi, e.g. Ceratocystis spp., which spread through phloem and xylem, blocking transport systems of the tree. The first adult beetles to attack a tree produce powerful pheromones that, together with resins exuding from the tree, attract other individuals of the same species. It is this combined attack by many beetles, together with the spread of pathogenic fungi that causes death of all or part of the tree. Because pheromones concentrate the flying beetle population in an area, dead trees often occur in patches.

Bark beetle outbreaks occur at irregular intervals but are usually associated with stands that are under stress. However, once outbreaks have been initiated, they sometimes spread into relatively healthy stands. This ability of bark beetles to kill normal healthy trees when their populations become large, i.e. their "aggressiveness", is associated with their tolerance of tree host defensive chemicals, the pathogenicity of fungi associated with them, and/or the attractiveness of their aggregation pheromones.

Ips sexdentatus, Tomicus piniperda, T. minor, Orthotomicus erosus, Pityogenes bidentatus and Hylastes ater are all bark-boring Scolytidae, and their populations can increase greatly if a stand contains high-risk trees. Thus, in order to avoid such pest population growth, all infested, broken, fallen and burnt trees must be removed, infestation points destroyed and a stand thinning plan implemented. Protection programmes must be established including the above measures, as well as monitoring of the insect population levels (e.g. by use of pheromone traps), attracting the beetles to trap trees, and/or biological control. The timber must be protected from post-logging damage by being debarked immediately after logging or, at most, within two weeks. Any trees found to be infested should be burned and cultural techniques altered to improve stand health.

Dioryctria sylvestrella (Lepidoptera, Pyralidae) is also a bark-boring insect pest, which particularly damages young trees; appropriate silvicultural techniques help to control it: low plantation densities should be avoided because they stimulate attacks by this pest. Matsucoccus feytaudi (Homoptera, Margarodidae) attacks weaken trees, making them susceptible to attacks from Pissodes castaneus and Tomicus piniperda. For the control of this species, debarking of infested logs is recommended, followed by the burning of the bark.

Root pests

In general, these insects are not a serious problem in established P. pinaster stands that have well-developed and extensive root systems. However, they may provide entry for root decay fungi. In nurseries and newly stocked plantations, on the other hand, root pests can cause severe problems because roots are small and fragile. This problem is intensified when soil cultivation or site preparation removed the other vegetation on the site. With most of their food destroyed, root insects are then forced to feed on the roots of the planted stock. Agriotes spp. (Coleoptera, Elateridae) can be controlled by appropriate silvicultural techniques, such as soil tillage which exposes the eggs and larvae. Moist soils are favourable to the development of Agriotes spp.

Hylastes spp. (Coleoptera, Scolytidae) may flourish in stands which have suffered fire, or in which planting techniques were inadequate, or in which there are many exposed, freshly-felled stumps, or successive drought years. Control can be via traps installed on the edge of plantations. In nurseries and recently forested areas, attacked trees should be uprooted and burned. Anoxia australis, Vesperus xatarti and V. luridus (Coleoptera, Scarabaeidae) may be particularly damaging in forest nurseries and in young P. pinaster stands. These pests may be controlled by using suitable silvicultural practices, such as soil tillage at the beginning of autumn and the maintenance of natural vegetation strips between plantation lines: strips of cereal crops sown between the tree lines may attract these pests, as they prefer to feed on roots of Gramineae.

Nematodes

P. pinaster has shown to be susceptible to Bursaphelenchus xylophilus, a nematode that causes the pine wilt disease. In other pines, namely Japanese black pine (P. thunbergii), this nematode causes reductions in hydraulic conductance, associated with plant water stress, death of the parenchyma cells of the xylem and, eventually, tree death (Kozlowski and Pallardy, 1997).

Fungal pathogens

The evolution of a disease caused by fungus is conditioned by three factors: the susceptibility of the host, the virulence of the parasite and the presence or absence of factors favourable to development of the pathogen. Armillaria mellea is a cosmopolitan fungus for which there is no effective control method. In order to minimise the possibility of infection, adequate cultural techniques must be implemented, so increasing tree vigour. Plantations on previously infected sites must be avoided. Both infected and healthy trees in the neighbourhood must be pulled out of the soil and burnt. Infected areas can be disinfected using a broad-spectrum fungicide. Lophodermium spp. and Cyclaneusma niveum are difficult to control with chemicals. However, when important infections appear in a nursery, it is possible to apply a fungicide (ciproconazol).

Fire

Maritime pine is very susceptible to fire, especially in pure stands. Abundant understorey is a key factor in determining stand flammability. To minimise the risk of fire it is advisable not to allow large continuous stands of this species. It is also advisable to establish weed control plans, as well as to provide an infrastructure which will minimise the risk of fire spreading (fire breaks, roads, fuelbreaks) and facilitate fire fighting (water points, roads).

Descriptions of the principal insect pests are largely based on Berryman (1986).Insect damage to cones and seeds are minor in heavy cone crop years, but in the years following a heavy cone crop, the entire cone crop may be lost as a large insect pest population is concentrated to a much reduced food supply. Due to this, the greatest impact of cone and seed pests is found in seed production orchards, commonly attacked by the pine cone weevil Pissodes validirostris (Coleoptera, Curculionidae) and the cone worm Dioryctria mendacella (Lepidoptera, Pyralidae).Insects feeding on buds, shoots and twigs may cause substantial long-term damage, affecting plant growth and wood quality, and they may also weaken the tree, facilitating attack by other organisms. They are particularly important in young plantations. Serious infestations seem to be associated with particular site and stand conditions that affect the vigour and exposure of seedlings and saplings. Outbreaks of shoot moths frequently occur in stands growing in dry or poorly drained sites, or in sites that have suffered soil compaction, erosion or nutrient deficiencies. Moreover, tip and shoot insect pests often prefer open conditions which means that damage is most intense in sparsely stocked clear-cut areas and plantations.The pine shoot moth Rhyacionia buoliana (Lepidoptera, Tortricidae) is controlled with the use of growth inhibitors (diflubenzuron) in the spring (before the larvae penetrate the buds), by sexual pheromone trapping systems (to lure males) and by biological control (Adalia bipunctata is a predator of this species). Leaf-feeding defoliating insects attack forest trees of all ages, but outbreaks are often associated with older stands, overstocked stands, or stands growing on poor sites. The immediate effect of defoliation is a reduction in the vigour and growth of the tree. Reduction in growth may have a significant economic impact on timber production when large areas are affected. Defoliation sometimes results in considerable tree mortality, particularly when the forest has been subjected to other stress factors such as nutrient or water deficiencies, extreme competition, or old age. In addition, the weakened trees often become susceptible to tree-killing insects, such as bark beetles, which frequently cause extensive mortality following defoliator outbreaks. The pine processionary moth Thaumetopoea pityocampa (Lepidoptera, Thaumetopoeidae) is the most serious pest of P. pinaster in the Mediterranean region.A number of insect groups feed on or within the stems of forest trees but, of these, the bark beetles (Scolytidae) are by far the most destructive. Bark beetle adults bore into the bark of living or recently killed trees and lay their eggs in galleries constructed in the cambial region. At the same time, bark beetles may introduce pathogenic fungi, e.g., Ceratocystis spp., which spread through phloem and xylem, blocking transport systems of the tree. The first adult beetles to attack a tree produce powerful pheromones that, together with resins exuding from the tree, attract other individuals of the same species. It is this combined attack by many beetles, together with the spread of pathogenic fungi that causes death of all or part of the tree. As pheromones concentrate the flying beetle population in an area, dead trees often occur in patches. Bark beetle outbreaks occur at irregular intervals but are usually associated with stands that are under stress. However, once outbreaks have been initiated, they sometimes spread into relatively healthy stands. This ability of bark beetles to kill normal healthy trees when their populations become large is associated with their tolerance of tree host defensive chemicals, the pathogenicity of fungi associated with them, and/or the attractiveness of their aggregation pheromones. Ips sexdentatus, Tomicus piniperda, T. minor, Orthotomicus erosus, Pityogenes bidentatus and Hylastes ater are all bark-boring Scolytidae, and their populations can increase greatly if a stand contains high-risk trees. To avoid such pest population growth, all infested, broken, fallen and burnt trees must be removed, infestation points destroyed and a stand thinning plan implemented. Dioryctria sylvestrella (Lepidoptera, Pyralidae) is also a bark-boring insect pest, which particularly damages young trees. Low plantation densities stimulate attacks by this insect. Matsucoccus feytaudi (Homoptera, Margarodidae) attacks weaken trees, making them susceptible to attacks from Pissodes castaneus and Tomicus piniperda. Hylastes spp. (Coleoptera, Scolytidae) may flourish in stands which have suffered fire, or in which planting techniques were inadequate, or in which there are many exposed, freshly-felled stumps, or successive drought years. Anoxia australis, Vesperus xatarti and V. luridus (Coleoptera, Scarabaeidae) may be particularly damaging in forest nurseries and in young P. pinaster stands.P. pinaster has shown to be susceptible to Bursaphelencus xylophilus, the nematode that causes the pine wilt disease, also an invasive species. In other pines, namely Japanese black pine (Pinus thunbergii), this nematode causes a reduction in hydraulic conductance associated with plant water stress, death of xylem parenchyma cells, and eventually tree death (Kozlowski and Pallardy, 1997). P. pinaster is susceptible to the pathogens: Armillaria mellea, Lophodermium spp. and Cyclaneusma niveum.P. pinaster is very susceptible to fire, especially in pure stands. Abundant understorey is a key factor in determining stand flammability.

In recent years, P. pinaster has shown itself to be susceptible to another invasive species, the bast scale, Matsucoccus feytaudi (Homoptera: Margarodidae), in Corsica, France (Jactel et al., 2006).

Pinus spp. are probably the single most economic important genus of the trees in the world, and P. pinaster must rank within the top 50 commercially valuable species, giving it an economic value in excessive of very many millions of dollars per annum. The negative consequences of invasion, have not been accurately quantified either, however, it is clear that it the vast majority of situation, positive benefits outweigh negative ones. P. pinaster plantations have long been cultivated in the Mediterranean basin region, in both Europe and North Africa, also to stabilise sand dunes, coastal areas and on low fertility soils, and the tree has also been a major source of resin as well as general purpose timber.

Macdonald and Richardson (1986) name P. pinaster among several species that accelerate soil erosion when they establish in riparian systems in South Africa, and soil nutrient and water levels are altered during invasion (Weber, 2003). P. pinaster needles decay slowly, resulting in large quantities of litter (Versfeld and van Wilgen, 1986). Henderson (2001) reports the invasion of both montane and lowland fynbos and describes P. pinaster as a habitat transformer.

Impact on Biodiversity

Cronk and Fuller (1995) report that P. pinaster is outcompeting rare fynbos vegetation in South Africa, being able to do so because of its rapid growth rate, greater longevity and ability to withstand fire. Higgins et al. (1999) used environmental data to estimate the potential future area occupied by P. pinaster to be 23-49% of the Cape Peninsula, constituting a very high threat to native species diversity. Richardson et al. (1989) demonstrated that indigenous species richness was negatively correlated with P. pinaster canopy cover in certain areas of South Africa.

P. pinaster is widely planted for dune stabilization, enabling the agricultural use of large areas along the western coast of the Iberian Peninsula, and pine stands also serve as shelterbelts protecting agricultural crops against salt spray. In southwestern France it has also been used for sanitation plantations in the Landes region. P. pinaster has been used for soil conservation, including protection of slopes against erosion. Due to its fast growth characteristics and tolerance of poor soils, P. pinaster is often used for afforestation of abandoned agricultural land and as a shade tree in picnic areas, camp sites and recreational parks. However, one limitation to its use as an amenity tree is its susceptibility to soil compaction. P. pinaster has been traditionally considered a useful species for the improvement of thin soils because, as a pioneer species in the secondary ecological succession, it will encourage soil formation, i.e. roots will desegregate the rock and foliage will form a litter layer. In Portugal, this species is also used as a Christmas tree.

Wood is the major product that is obtained from P. pinaster. Its annual rings are very visible, creating a distinct and effective pattern to the timber; but the wood is susceptible to almost every defect imaginable in timber wood, and it is also very resinous. The main applications of P. pinaster timber include construction wood, furniture, roof shingles, shipbuilding, poles and posts for palisades and fencing, among others. It is also used for firewood, with cones and needles (after drying) also being used as kindling for starting fires.

Resin is the most important non-wood product from P. pinaster, being used, directly or indirectly after distillation, to make turpentine, pitch, oils, varnishes, adhesives, waxes and soap. It is also used for waterproofing. In the Landes, southwestern France, essential oil was produced from chipped crown materials (Alexandrian, 1992). The bark of P. pinaster may be distilled to produce tar, or chipped and composted to produce a low-weight substrate for nursery containers. P. pinaster stands also are an ideal ecosystem for the development of edible fungi, such as Boletus edulis, B. pinicola, Lactarius deliciosus and L. semisanguifluus.

Maritime pine is fast-growing until it reaches age 60 years, then growth rate usually declines. The species is often cultivated in even-aged stands due to the fact that it does not tolerate shade, and it is not usually possible to manage P. pinaster in uneven-aged monoculture stands, although it is possible to include P. pinaster in uneven-aged mixed species stands.

In the Iberian peninsula, annual volume increment of P. pinaster varies between 5 and 10 cubic metres/ha, and yields vary between 300 and 470 cubic metres/ha, depending on site quality. On good quality sites it is possible to achieve 30-year long rotations, although 35 years is the most common. However, on normal sites rotation length is 45 years, and on poor quality sites rotations of 60 to 80 years are the norm.

On poor sites in France (Gard department, and Corsica), the national forest inventory records mean annual volume increments of between 4 and 5 cubic metres/ha. On the best sites in the Landes region, annual volume increments can reach 14 cubic metres/ha; this rate is for trees aged 20 to 40 years; thereafter, increment decreases (Alexandrian, 1992).

Maritime pine shows a high degree of genetic variation over its natural range. Some authors recognize as many as five different races, corresponding to several geographical locations in Western Europe, the Mediterranean region and North Africa. Most of that variation has some kind of expression in growth characteristics, stem straightness and taper, fine branching and frost resistance. A high degree of heritability was particularly shown for stem form, as well as for the chemical characteristics of resin monoterpenes.Provenances from Portugal, Galicia in N. Spain and the Landes area of SW France (P. pinaster subsp. atlantica) have exhibited faster growth than those from the Mediterranean, inland Spain or Morocco (mainly P. pinaster subsp. pinaster). However, some provenances of the latter group have a remarkably straight stem (e.g. the Corsican race), or a notable adaptation to summer drought and limestone substrates, regardless of their lack of vigour (e.g. the Moroccan race from Tamjout), compared to provenances of the former group.The Portuguese provenance of Leiria (central coastal Portugal) was genetically improved in western Australia, South Africa and Portugal, allowing a growth gain estimated to be 20%, as well as an improvement of about 40% for stem form.

The major disadvantage of maritime pine is its susceptibility to fire, because of the highly flammable resinous needles and wood, and due to the fact that, throughout most of the Mediterranean region, the low-density crown allows the growth of a shrubby, evergreen understorey that increases fire risk.In some areas of the world P. pinaster is an aggressive colonizer, particularly in coastal dune areas (Uruguay), along road verges, Banksia sp. and Eucalyptus marginata woodlands (Australia), grassland slopes, cliff faces, cut-over forests, scrub and shrublands (New Zealand), fynbos (South Africa) and disturbed sites (Chile).