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21 November 2019

Pinus patula (Mexican weeping pine)

Datasheet Types: Tree, Invasive species, Host plant

Abstract

This datasheet on Pinus patula covers Identity, Overview, Associated Diseases, Pests or Pathogens, Distribution, Biology & Ecology, Environmental Requirements, Uses, Management, Genetics and Breeding, Economics, Further Information.

Identity

Preferred Scientific Name
Pinus patula Schiede ex Schltdl. & Cham.
Preferred Common Name
Mexican weeping pine
Variety
Pinus patula var. longipedunculata Loock ex Martínez
Pinus patula var. patula
Other Scientific Names
Pinus patula var. macrocarpa M. T. Masters
International Common Names
English
patula pine
spreading-leaved pine
Spanish
ocote
pino chino
pino patula
French
pin argente
Local Common Names
Brazil
pinheiro
Germany
Kiefer, Ausgebreitete
Kiefer, Mexikanische
Mexico
ocote
EPPO code
PIUPT (Pinus patula)

Pictures

22 year old tree.
Tree habit
22 year old tree.
B.I. Nyoka
22 year old natural stand.
Natural stand
22 year old natural stand.
B.I. Nyoka
Plantation, Woodbush, South Africa.
Plantation
Plantation, Woodbush, South Africa.
Environmentek, CSIR, South Africa
Foliage
Gerrit van Wyk
Female flowers
B.I. Nyoka
Male flowers
B.I. Nyoka
Cone
B.I. Nyoka

Overview

Importance

P. patula is a medium-size tree (usually to 20 m tall) native to eastern Mexico. It is the most important pine species in southern and East Africa (Kenya, Malawi, Mozambique, Zambia, Zimbabwe, South Africa, Swaziland, Tanzania and Uganda) and is commercially planted in South America (Colombia, southern Brazil, Argentina) and, to a limited extent, in Asia (Nepal and India). It has a light coloured timber with medium density, useful for lumber. Although pulp yield is lower than that of P. elliottii and P. taeda, P. patula is favoured for groundwood pulp because it is less resinous. It is best adapted to high altitudes with cool climates (mean annual precipitation greater than 1100 mm, a mean annual temperature of 14°C and summer rainfall). When planted in hot, humid conditions at low altitudes, it is susceptible to infection by Sphaeropsis sapinea after hail damage. It responds readily to genetic improvement for increased growth rate, stem form, and branching. It is an invasive species of both fire-climax grasslands and woodland in exotic situations where climatic conditions are close to those found in its natural range.

Although most of the countries in which it is planted as an exotic have some form of breeding programmes for P. patula, by far the most advanced genetic improvement programmes supplying genetically improved seed are in South Africa and Zimbabwe. The focus of these breeding programmes has been to improve stem form, taper, volume, branch size, crown size and form. By and large, success has already be achieved in most of these traits where timber yields for example, have now been increased by as much as 35% after two generations of breeding and selection (Barnes, 1977).

Summary of Invasiveness

P. patula is a medium-size tree (usually to 20 m tall) native to eastern Mexico. It is the most important pine species in southern and East Africa (Ethiopia, Kenya, Malawi, Mozambique, Zambia, Zimbabwe, South Africa, Swaziland, Tanzania and Uganda) and is commercially planted in South America (Colombia, southern Brazil, Argentina) and, to a limited extent, in Asia (Nepal and India). The major problem of P. patula is its aggressiveness and weediness. Introduced P. patula has been found to be associated with invasion events in Hawaii (USA), South Africa, Zimbabwe, Botswana, Malawi (Haysom and Murphy, 2003) and Madagascar and New Zealand (Richardson and Rejmánek, 2004a). It is an invasive species of both fire-climax grasslands and woodland in exotic situations where climatic conditions are close to those found in its natural range.

Taxonomic Tree

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Notes on Taxonomy and Nomenclature

The genus Pinus, with over 100 species, is a taxon found almost exclusively in the northern hemisphere. The taxon is also notable among the Coniferae because it has its greatest diversity in Mexico and the western USA, rather than in China and Japan where most of the diversity of the remainder of the family Pinaceae is concentrated (Farjon, 1998).

Description

Habit and size

In its native range, P. patula is said to be a graceful tree, height 12-20 (30 m or occasionally to 30-40 m) with d.b.h. up to 120 cm. In plantations outside its native range, tree heights of between 35 and 50 m have been recorded, at ages ranging from 20 years to 50 years (Loock, 1950; Styles et al., 1975).

The crown shape usually depends on both spacing as well as inherent variability of the trees. Open grown trees tend to have spreading crowns while closely spaced trees tend to have narrow crowns with good suppression of lower branches which subsequently die. Some trees will still have deep narrow crowns even when growing in the open. Although branching is said to be irregularly placed on the stem (Loock, 1950), in exotic environments branching tends to be regular with on average four branches per whorl, but the distance between whorls is variable. Foxtailing occasionally occurs but the majority of trees tend to be multi nodal with average distance between whorls of about 0.4 m. Within the native distribution range, branches have been reported to be pendent whereas in exotic environments, particularly Africa, the branches are borne at an angle above the horizontal. Branch size is very variable from fine branching to very thick branches.

Stem form

Stem form in P. patula is also very variable. Although atrociously crooked trees can be found in this species, stem form is generally moderate to good. Good specimen trees with straight cylindrical stems that retain apical dominance to the age of 30 years or more are quite common. Common defects include forking, sometimes caused by mechanical damage such as bird perching, butt sweep, bow, sinuosity and nodal swellings; such stem features are usually found in trees growing in warm lower altitude environments.

Bark

Bark is thick, rough and scaly with large elongated plates and deep, longitudinal fissures especially on the lower part of the bole, bark colour is dark grey-brown on lower trunk, and higher up and on younger trees bark is reddish-brown or orange, thin and papery (Vidakovic, 1991). The age at which mature bark appears is not yet known, but appears to vary with site. Some trees have been observed to develop completely smooth bark at lower, drier altitudes.

Crown

The crown may be rounded or spire-like with needles borne on pendent secondary branches. Branching may be from the ground. Young shoots are more noded, glaucous green, becoming reddish-brown in the second year.

Foliage

Buds cylindrical, 15-25 mm long, covered with long pointed, fringed scales, which are not resinous and spreading at the tips. Needles are borne in fascicles of 4 (may be 3 or 5), in drooping or spreading tufts, 15 to 30 cm long, very thin, and of a shiny light to yellowish-green in colour. Stomata lines on all needle surfaces; resin ducts 2-3, usually medial, sheaths slender, persistent, 10-25 mm long. Needles may persist for two to three years.

Inflorescences, flowers and fruit

Flowering in P. patula varies from site to site. In its native range, pollen shedding begins in January and lasts until April and wide tree to tree variation is observed. In Malawi, Zimbabwe and South Africa, flowering (both male and female flowers) occurs in spring, i.e., August to October. A secondary flush of only female flowers usually occurs earlier in the year (Barnes and Mullin, 1974; Drew, 1969). In Kenya which is very close to the equator, two flushes of both flowers occur coinciding with the two rainy seasons (April-May and October-November). Female flowers have also been recorded throughout the year. In Zimbabwe, studies showed that synchronisation of pollen shedding with female receptivity is good at altitude 1500 m, whereas pollen rain became progressively later at lower altitudes.

Cones

Conelets are usually lateral, rarely subterminal, persistent, somewhat oblong, ovate-conical, curved, oblique at base, tapering towards apex, sessile, rarely subsessile, single or in clusters of 2-5, up to 10 or even more. Cone size 4-9 cm long, pale brown, hard, strong, scales oblong with raised apophyses on which there is a minute prickle. Seed triangular, grey mottled with black, 5 mm long, wing 12-18 mm long (Vidakovic, 1991; Loock, 1950).

Observations on lack of natural regeneration at lower altitudes in Zimbabwe appear to indicate that at lower altitudes seed is probably empty (infertile); at higher altitudes natural regeneration occurs. Cones, which usually take two years to mature, are harvested in September-October.

P. patula flowers as early as age 2 years with female flowers appearing first and male flowers appearing in the fourth year. Five-year old trees produce viable seeds and cone and seed production is prolific by the eighth to the tenth-year.

Botanical Features

Habit and size

In its native range, P. patula is said to be a graceful tree, height 12-20 (30 m or occasionally to 30-40 m) with d.b.h. up to 120 cm. In plantations outside its native range, tree heights of between 35 and 50 m have been recorded, at ages ranging from 20 years to 50 years (Loock, 1950; Styles et al., 1975).

The crown shape usually depends on both spacing as well as inherent variability of the trees. Open grown trees tend to have spreading crowns while closely spaced trees tend to have narrow crowns with good suppression of lower branches which subsequently die. Some trees will still have deep narrow crowns even when growing in the open. Although branching is said to be irregularly placed on the stem (Loock, 1950), in exotic environments branching tends to be regular with on average four branches per whorl, but the distance between whorls is variable. Foxtailing occasionally occurs but the majority of trees tend to be multi nodal with average distance between whorls of about 0.4 m. Within the native distribution range, branches have been reported to be pendent whereas in exotic environments, particularly Africa, the branches are borne at an angle above the horizontal. Branch size is very variable from fine branching to very thick branches.

Stem form

Stem form in P. patula is also very variable. Although atrociously crooked trees can be found in this species, stem form is generally moderate to good. Good specimen trees with straight cylindrical stems that retain apical dominance to the age of 30 years or more are quite common. Common defects include forking, sometimes caused by mechanical damage such as bird perching, butt sweep, bow, sinuosity and nodal swellings; such stem features are usually found in trees growing in warm lower altitude environments.

Bark

Bark is thick, rough and scaly with large elongated plates and deep, longitudinal fissures especially on the lower part of the bole, bark colour is dark grey-brown on lower trunk, and higher up and on younger trees bark is reddish-brown or orange, thin and papery (Vidakovic, 1991). The age at which mature bark appears is not yet known, but appears to vary with site. Some trees have been observed to develop completely smooth bark at lower, drier altitudes.

Crown

The crown may be rounded or spire-like with needles borne on pendent secondary branches. Branching may be from the ground. Young shoots are more noded, glaucous green, becoming reddish-brown in the second year.

Foliage

Buds cylindrical, 15-25 mm long, covered with long pointed, fringed scales, which are not resinous and spreading at the tips. Needles are borne in fascicles of 4 (may be 3 or 5), in drooping or spreading tufts, 15 to 30 cm long, very thin, and of a shiny light to yellowish-green in colour. Stomata lines on all needle surfaces; resin ducts 2-3, usually medial, sheaths slender, persistent, 10-25 mm long. Needles may persist for two to three years.

Inflorescences, flowers and fruit

Flowering in P. patula varies from site to site. In its native range, pollen shedding begins in January and lasts until April and wide tree to tree variation is observed. In Malawi, Zimbabwe and South Africa, flowering (both male and female flowers) occurs in spring, i.e., August to October. A secondary flush of only female flowers usually occurs earlier in the year (Barnes and Mullin, 1974; Drew, 1969). In Kenya which is very close to the equator, two flushes of both flowers occur coinciding with the two rainy seasons (April-May and October-November). Female flowers have also been recorded throughout the year. In Zimbabwe, studies showed that synchronisation of pollen shedding with female receptivity is good at altitude 1500 m, whereas pollen rain became progressively later at lower altitudes.

Cones

Conelets are usually lateral, rarely subterminal, persistent, somewhat oblong, ovate-conical, curved, oblique at base, tapering towards apex, sessile, rarely subsessile, single or in clusters of 2-5, up to 10 or even more. Cone size 4-9 cm long, pale brown, hard, strong, scales oblong with raised apophyses on which there is a minute prickle. Seed triangular, grey mottled with black, 5 mm long, wing 12-18 mm long (Vidakovic, 1991; Loock, 1950).

Observations on lack of natural regeneration at lower altitudes in Zimbabwe appear to indicate that at lower altitudes seed is probably empty (infertile); at higher altitudes natural regeneration occurs. Cones, which usually take two years to mature, are harvested in September-October.

P. patula flowers as early as age 2 years with female flowers appearing first and male flowers appearing in the fourth year. Five-year old trees produce viable seeds and cone and seed production is prolific by the eighth to the tenth-year.

Distribution

The natural range of distribution of Pinus patula is entirely confined to Mexico. The two known varieties of this species are P. patula var. patula and P. patula var. longipedunculata.

P. patula
introductions have been planted in both the cool and wet tropical and subtropical regions of the world. In tropical regions the introductions are mostly at altitudes above 2000 m where conditions for optimum growth of this species are found. In the subtropical regions, the species has been planted in wetter but slightly lower altitudes of about 900 m. Overall P. patula is now grown from the equator (in Colombia) to as far as latitude 42 degrees South in New Zealand (Styles et al., 1975).

Review of Natural Distribution

The natural range of distribution of Pinus patula is entirely confined to Mexico. The two known varieties of this species are P. patula var. patula and P. patula var. longipedunculata.

Pinus patula var. patula
This variety is found in a few localities in the state of Tamaulipas, in QuerÚtaro, Hildago, Mexico Distrito Federal, Morelos, Tlaxcala, Puebla, Vera Cruz, Oaxaca and Chiapas (Farjon and Styles, 1998). Its main distribution is on the Sierra Madre Oriental and the high mountains of east-central Mexico. The altitudinal range of distribution spans 1900 m, from altitude 1400 m to a high of 3300 m, but is concentrated between altitude 1800 and 2800 m (Perry, 1991; Farjon and Styles, 1998). This variety is generally restricted to humid, subtropical to warm temperate sites with an annual precipitation of 1000 to 2200 mm per annum. The species occurs in a variety of mesic forest types, associated with other pines such as Pinus pseudostrobus, P. greggii, P. maximinoi, P. hartwegii and P. ayacahuite. At some locations it also occurs together with Abies religiosa, mixed with pine-oak forests and also with Liquidambar.

Pinus patula var. longipedunculata
This variety is only known from two localities in the states of Hildago and Vera Cruz but is more wide spread in Oaxaca and central Chiapas. Its ecology is very similar to var. patula, but its ecological amplitude is however narrower.

P. patula has almost naturalised itself in southern Africa (South Africa and Zimbabwe) where it naturally regenerates itself and has taken over as the dominant species on some grasslands as well as in some forests in cool wetter areas, where it produces viable seed.

Location of Introductions

P. patula introductions have been planted in both the cool and wet tropical and subtropical regions of the world. In tropical regions the introductions are mostly at altitudes above 2000 m where conditions for optimum growth of this species are found. In the subtropical regions, the species has been planted in wetter but slightly lower altitudes of about 900 m. Overall P. patula is now grown from the equator (in Colombia) to as far as latitude 42°S latitude in New Zealand (Styles et al., 1975).

Introductions of P. patula can be found in southern Africa (Malawi, Mozambique, South Africa, Swaziland, Zambia and Zimbabwe), east Africa (Burundi, Ethiopia, Kenya, Madagascar, Tanzania, Uganda, Rwanda), west and central Africa (Cameroon, Nigeria, Democratic Republic of Congo (Zaire), Asia (Australia, India, Sri Lanka, Papua New Guinea, New Zealand), South America and the Caribbean (Argentina, Brazil, Colombia, Ecuador, Venezuela, Jamaica) and in Mexico (Styles et al., 1975; Poynton, 1979). Most of these plantings were evaluation tests, pilot plantings and commercial plantings. P. patula is mainly intended for timber as well as for the pulp and paper industry.

Distribution Map

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Distribution Table

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Biology and Ecology

Climate

The precipitation in the P. patula natural distribution range varies from 1000 to 2200 mm per annum. Rainfall is received in summer with a relatively short winter dry season which is ameliorated by frequent fog and mist outside the rainy season. Average annual temperatures vary from 9.3°C to 23.3°C. The number of frost days vary from 8 to 101 days per year.

In exotic environments, P. patula thrives in areas with summer rainfall (South Africa, Zimbabwe, Swaziland and Malawi) and in monsoonal two peak rainfall areas in east Africa (Kenya and Tanzania) where majority of the rain falls in the relatively cooler season (Styles et al., 1975). In New Zealand, although a very minor species now, the area receives winter rainfall. P. patula will do well in areas with more than 750 mm of precipitation per annum, as long as rainfall distribution is good and the dry season is short. Temperature does not appear to seriously affect P. patula growth as the species has been successfully grown as far south as latitude of 40°S in New Zealand. The species tolerates light frost when it is actively growing and will tolerate temperatures of up to -10°C provided it is dormant. Studies have shown that, of rainfall and temperature, the latter will be more critical in determining productivity of P. patula (Styles et al., 1975). Temperature is in turn governed by altitude as well as latitude.

Soil and Physiography

Pinus patula grows on a wide range of soils. In its native range the species grows on deep fertile clay as well as loose, porous sandy loam soils. In exotic environments, the species thrives on young volcanic soils in South America and East Africa, mature leached infertile soils derived from the basement complex in South Africa, doleritic soils, as well as soils derived from schist. The species prefers acidic soils that have a good moisture supply (Poynton, 1979). Typically, deep soils that retain moisture throughout the dry season are ideal for P. patula. Besides soil depth, rooting depth is also critical as studies have shown that P. patula will grow on shallow soils of only 15 cm depth, by the ability to send roots through fissures of rock.

The species grows on almost all major land forms. There are no known preferences for aspect and the species has been recorded growing on all kinds of slopes, ridges, flat plains and ravines.

Vegetation Types

cloud forests
deciduous forests
mixed forests
moist forests
mountain forests

Latitude/Altitude Ranges

Latitude North (°N)Latitude South (°S)Altitude lower (m)Altitude upper (m)
241612503300

Air Temperature

ParameterLower limit (°C)Upper limit (°C)
Absolute minimum temperature-10 
Mean annual temperature923
Mean maximum temperature of hottest month1528
Mean minimum temperature of coldest month614

Rainfall

ParameterLower limitUpper limitDescription
Dry season duration04number of consecutive months with <40 mm rainfall
Mean annual rainfall10002200mm; lower/upper limits

Rainfall Regime

Summer
Winter
Bimodal

Soil Tolerances

Soil texture > light
Soil texture > medium
Soil texture > heavy
Soil reaction > acid
Soil reaction > neutral
Soil drainage > free
Special soil tolerances > shallow
Special soil tolerances > infertile

Soil Types

clay soils
luvisols
mountain soils
podzols
sandy soils
tropical soils
vertisols
volcanic soils

Notes on Pests

Fungal diseases

P. patula is not attacked by many pests and diseases. In the nursery it is important to keep an eye on damping-off diseases, the chief causal agents are Rhizoctonia solani, Fusarium spp. and Pythium spp., although there are other pathogens which have also been blamed for damping-off. Damping off is usually associated with overwatering. Chemical control is by fungicides.

In the field, P. patula may be attacked by Dithostroma pini after the trees have been damaged by hail. Other fungal pathogens are Diplodea pinea, Sphaeropsis ellisii, Armillaria mellea.

Insect pests

Pests of P. patula in its natural range are poorly documented. In exotic environments, many pests have been recorded but most of these do not appear to cause economic damage. They include the grasshopper Mecostibus pinivora in Zimbabwe, several coleopterans, larvae of several lepidopterans, and aphids. The wood wasp Sirex noctilio and its associated fungus Amylostereum areolatum have infested plantations of P. patula.

List of Pests

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Uses

Uses: Wood Uses

The wood of P. patula can be sawn easily both when wet and dry (Styles et al., 1975). Logs and sawntimber are, however, susceptible to blue stain. To avoid this, logs have to be quickly transported and sawn as soon as possible and sawn timber may be dipped in anti-stain solutions. The sawn timber may be seasoned by air or kiln drying. The wood is soft, light and reasonably strong. The wood is white to yellowish-white in colour with a pinkish heart which is difficult to distinguish from the sapwood. The average density of green wood is 880 kg/cubic metre and at 10% moisture the average density is 450 kg/cubic metre (range 350 to 610). The wood contains very little resin and has a very faint odour (CSIR, 1986). Other important strength properties are: bending strength 82 MPa, compression parallel to grain 46.0 MPa, shear 8 Mpa, modulus of elasticity 11390 MPa, hardness 2960 N and toughness 19Nm (CSIR, 1986).

P. patula shows wide variation in wood properties. The variation is between provenances, families, tree to tree and within tree and between growing site conditions. Density decreases from the pith outwards for the first few rings, then increases steadily. Fibre length increases steadily from the pith.

P. patula wood is not resistant to fungus, insect and termite attack and in external conditions the wood deteriorates rapidly. Vacuum pressure treatment with preservatives has been shown to improve the lifespan of the timber. The timber and moulds easily. It takes nails without splitting and also takes glue easily. The wood is too soft for high-class furniture or joinery manufacture unless used in thick sections and coated with a hard finish. The wood is suitable for composite board manufacture and can be used for panelling and decorative purposes. The wood is attractive in appearance because of the colour contrast between early and late wood. The wood can also be used for wood-wool cement slabs and particleboard manufacture. The species can also be used for pulp by the kraft process. The fibre length varies from 2 to 5 mm.

The major limitation of P. patula species is the large size of the juvenile core wood which is blamed on the fast growth rate of the young trees. Various environmental and genetic approaches have been suggested to manipulate the size of the juvenile core wood.

Uses: Land Uses

Because the species produces a lot of litter, it is possible that it can be used for soil conservation and erosion control although there are no referenced cases where it has been so used. There are no known reports of using this species in soil improvement planting. P. patula is not wind firm, therefore is not likely to be useful for shelterbelts or windbreaks. As P. patula is an aggressive colonizer, it is possible to use it in revegetation and land reclamation works. P. patula may be grown along avenues and in gardens as an ornamental species, although this use is not widespread.

Uses List

General > Ornamental
Environmental > Erosion control or dune stabilization
Environmental > Shade and shelter
Materials > Carved material
Materials > Fibre
Materials > Gum/resin
Materials > Miscellaneous materials
Materials > Wood/timber
Medicinal, pharmaceutical > Traditional/folklore
Fuels > Charcoal

Wood Products

Charcoal
Containers > Boxes
Containers > Cases
Containers > Crates
Containers > Pallets
Furniture
Pulp > Long-fibre pulp
Roundwood > Posts
Roundwood > Transmission poles
Sawn or hewn building timbers > Beams
Sawn or hewn building timbers > Carpentry/joinery (exterior/interior)
Sawn or hewn building timbers > Flooring
Sawn or hewn building timbers > For heavy construction
Sawn or hewn building timbers > For light construction
Sawn or hewn building timbers > Shingles
Sawn or hewn building timbers > Wall panelling
Veneers
Wood wool
Wood-based materials > Laminated veneer lumber
Wood-based materials > Laminated wood
Wood-based materials > Particleboard
Wood-based materials > Plywood
Wood-based materials > Wood cement
Woodware > Brushes
Woodware > Cutlery
Woodware > Industrial and domestic woodware
Woodware > Tool handles
Woodware > Toys

Silviculture Characteristics

Tolerates > frost
Ability to > regenerate rapidly
Ability to > self-prune

Silviculture Practice

Seed propagation

P. patula is propagated from seed, collected from either rogued seed stands, seedling seed orchards or clonal seed orchards. In countries such as Swaziland, Zimbabwe and South Africa, P. patula plantations have originated been from improved seed collected from clonal seed orchards since the establishment of orchards in the 1960s.

Vegetative propagation

Although there are studies looking at the potential of vegetative propagation of P. patula for commercial planting, most of the plantings are still made from seed. However, clonal orchards are established using clones propagated by grafting and, in a few cases of incompatibility, air layering has been used to propagate the clones (Barnes, 1974).

Nursery practice

For maximum growth with the shortest possible time, it is best to site a nursery for production of P. patula seedlings on a warm site and this is usually between altitudes of 600 to 1200 m. At such low altitudes, it is possible to have plants of plantable size (15 to 20 cm height) in less than seven months (Styles et al., 1975).

Percentage germination may be improved through seed pretreatment to break dormancy. Soaking in cold water for eight days has been reported to break dormancy in seed that was 1 to 7 years old (Barrett, 1973; Pudden, 1956). Soaking in hydrogen peroxide (1 kg of seed in 80 litres of 1.5% hydrogen peroxide for 4 days) was found to increase germination. Scarification was found to be ineffective for P. patula. Another method of improving germination is to separate empty seeds from filled seeds by floating out the empty seeds.

Seed may be sown in nursery beds or in pots or planta flats. If sown in nursery beds, they may still be pricked out into pots. The nursery soil must be slightly acidic with good drainage. The soil should also have essential nutrients, retain moisture, adhesive to form a root ball and mycorrhizal fungi. Addition of gravel or sand improves drainage, artificial fertilisers can provide a source of nutrients, organic matter will improve water retention, whilst clay soils will improve soil adhesion. Soil collected from under a pine stand is a good source of mycorrhizal fungal. Drainage may be improved by use of raised seed beds. Soil sterilisation may be necessary if the soil is suspected of harbouring pathogens. As in any nursery, it is important to control watering, pests, diseases, weeds, root pruning, etc.

Plants are ready for field planting once the trees are more than 15 cm in height. This is usually achieved in about seven months. The best time of planting is when the ground is sufficiently moist, unless irrigation is envisaged.

Site Preparation

The amount of site preparation depends on the quality or state of the site. In dry areas deep ploughing will eliminate weeds and possibly improve moisture retention through improved soaking. On grassland sites, usually site preparation just involves pitting accompanied by spot weeding (mechanically or chemically) or slashing of grass or ploughing and discing if the land is flat and resources permit.

If planting is within forest or wooded areas, then the other trees have to be cleared before the land is ploughed and pitted. Again, ploughing will depend on slope of the land and resources available.

Stand establishment

Natural regeneration

Although P. patula regenerates easily, it has not been established from natural regeneration mainly because most countries use improved seed to produce planting stock.

Direct sowing

There are also no records of the establishment of P. patula from direct sowing in the field. In any case, the improved seed used is expensive, and most companies would not opt for this method which uses more seed than the use of planting stock.

Planting stock

This remains the only method that is used for field establishment of P. patula.

Spacing

The commonest spacings used today for P. patula vary from 2.4 x 2.4 m to 3 x 3 m squares. Rectangular spacings are used in case access by machinery is required. The ultimate spacing depends on several factors. Blanking (gap filling) is a debatable issue: some forestry companies consider it to be a waste of resources, particularly if the growing season is good, as P. patula grows so fast that 'filler' plants never catch up. Other companies, however, do undertake gap filling even up to the third year after plantation establishment. Large planting stock is recommended for blanking.

Weed control

Weeding mechanically or chemically can be done depending on weed competition and resources. Some forestry companies control weeds up to the third year, whilst other companies consider it a waste of resources particularly on grasslands.

Fertilisers

There have been reports that soil fertility declines in the second, third and subsequent rotations. Evidence, although still scanty, indicates that growth actually may increase after the first rotation. There are currently no conclusive experiments on fertiliser use of P. patula. Some studies have indicated that forking in P. patula may be caused by boron deficiency.

Thinning

Timing of thinning depends on initial spacing, site quality, end product (i.e. sawlog versus pulpwood) and availability of resources. For sawlogs the aim is to get a final crop or stand of more than 400 trees per hectare with mean breast height diameter of about 45 cm at rotation, which in Zimbabwe and South Africa may be 25 to 35 years depending on site quality. For pulpwood, breast height diameters of about 30 cm after 15 to 25 years are considered normal. The are also reports that thinning can be used to manipulate wood quality in South Africa, although the results are still conflicting. Thinning may also be used to open up stands against wind, or to reduce stocking where moisture is limiting.

There are many techniques of thinning that are practised. One may select trees eclectically at an early age and these trees receive preferential treatment throughout. This is useful where trees do not change in quality, but experience has shown that they do change with age. Another method is mechanical or systematic thinning of every alternate tree or row depending on thinning intensity. Thinning may be removal of inferior trees at the time often called silvicultural thinning or cleaning.

In Zimbabwe for example, from an initial stocking of 1111/ha (at 3x3 m) a first thinning (40% removed) is usually done between age 6 and 8 years, to leave 666 trees/ha. A second and final thinning (40% removed) at age 12-15 years reduces stocking to about 400 stems/ha. At higher initial stockings, a third thinning is often necessary at about age 15-18 years.

Pruning

Pruning may be low or high. High pruning, which involves removal of both dead and live branches, is usually intended to produce clear knot-free timber which is considered high grade timber, while low pruning is undertaken to reduce fire hazard and improve access. Generally high pruning is for sawn timber while trees destined for pulpwood receive low pruning.

Silviculture Practice

Seed storage > orthodox
Vegetative propagation by > cuttings
Vegetative propagation by > air layering
Vegetative propagation by > grafting
Vegetative propagation by > tissue culture
Stand establishment using > natural regeneration
Stand establishment using > planting stock

Management

Like other commonly cultivated timber species, timber yields from P. patula vary with site quality. Mean annual increments reported vary from 9.9 cubic metres/ha to as much as 40 cubic metres/ha. In southern Africa, the mean annual increments range from 18 cubic metres/ha to 28 cubic metres/ha (Styles et al., 1979). The high mean annual increments are in East Africa where the dry season is very short.

Genetic Resources and Breeding

P. patula is one of the most successful stories of domestication and genetic improvement of subtropical pines. The first provenance collections were made in Mexico in 1947 (Loock, 1950). Since then expeditions were made to collect more provenances of this species by different organizations, countries and by the Food and Agriculture Organization (FAO) of the United Nations.

Provenance trials

Material from early collections was tested in provenance and progeny trials in Argentina, Brazil, Colombia, Kenya, Malawi, Mexico, Swaziland, South Africa and Zimbabwe. There are, however, reports that most of the collections did not cover the species' entire range. In the 1980s the Central America and Mexico Coniferous Resources (CAMCORE) cooperative made extensive collections of germplasm of P. patula in its native range and the material has been further tested in some of these countries.

The material that gave rise to the large plantations and breeding populations of southern and eastern Africa is believed to have originated from a very restricted source. Furthermore, the actual source is not known, although there is a possibility that the Los Reyes from Hildago provenance could be one of the sources. The fact however is that the success of this species was obviously achieved without any attempt at searching out the most suitable provenance.

In provenance trials in Zimbabwe outstanding provenances were: Acaxochitlan, Los Reyes, Encarnation (Hildago), Teopoxco (Oaxaca), Tlaxiipa and Huachinango (Pueblo) (Barnes and Mullin, 1984).

Genetic variation

Studies that have been carried out have shown wide variation in most economic traits (Barnes, 1973; Denison, 1973; Barnes and Schweppenhauser, 1978, 1979; Nyoka et al., 1992; Barnes et al., 1992; Ladrach, 1987). Traits studied and requiring genetic manipulation include volume, stem form or straightness, crown size and shape, branch size and habit and wood quality. Significant differences between families, in general combining ability and in specific combining ability have been reported between progenies in both open pollinated as well as control pollinated for volume, stem form or straightness, crown size and shape, branch size and habit and wood quality (Ladrach 1987; Barnes et al., 1992). Positive and favourable additive genetic and phenotypic correlations have also been recorded between traits. Heritability estimates have been estimated for Zimbabwean, Colombian and South African breeding populations (Barnes, 1973; Barnes and Schweppenhauser, 1978, 1979; Nyoka et al. 1992; Barnes et al., 1992; Ladrach, 1987; Denison, 1973). They range from 0.27 to 0.82. Genetic gains for volume from the first generation breeding in Zimbabwe was about 18% (Barnes, 1977) and up to 11% in east Africa (Patterson, 1968, 1969).

There are however conflicting reports on genotype-environment interaction in P. patula, with some studies reporting significant interactions whilst others found interactions to be negligible both at family and population level.

Breeding programmes

Most breeding programmes have a gene conservation aspect. CAMCORE has been particularly advocating the planting of some ex situ field gene banks of Mexican and central American pines which include P. patula. In Zimbabwe selected plus trees are preserved in field clone banks even if they may have been rejected in the breeding programme. All these are deliberate efforts to not only utilize but conserve the genetic resources of this important pine species.

Hybridisation

P. patula has shown potential in interspecific hybrid combination with other pines and currently there are active programmes developing hybrids of P. patula with P. greggii, P. pringlei, P. oocarpa in Zimbabwean and South African breeding programmes. Most of the hybrid tests are still very young and therefore there are no conclusions as yet on the best interspecific combinations.

Reproductive behaviour

Pinus patula flowers from about age two to three years (female flowers). Male flowers normally appear a year or two later. The species is predominantly wind pollinated and outcrossing but often tolerates a fair amount of inbreeding.

Disadvantages

The major problem of P. patula is its aggressiveness and weediness. In South Africa, Swaziland and Zimbabwe, P. patula is now considered a serious weed that has invaded grasslands and other vegetation types.

Links to Websites

NameURLComment
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.

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