PINUS UNCINATA: CHARACTERISTICS, HABITAT, NUTRITION - BIOLOGY - 2025

Pinus uncinata or black pine is a coniferous tree belonging to the Pinaceae family. The seed cones have a backward curved, hooked process. Its natural habitat is the mountains of Western Europe.

It grows in humid soils, located at altitudes above 1,000 meters above sea level. It is a species that is tolerant to cold temperatures. Its height ranges between 10 and 20 meters. The cup is conical, pyramidal, with some ramifications at its base. Its trunk is cylindrical in shape and grows straight, although on some occasions they can develop in a tortuous way.

By S. Rae from Scotland, UK (Pinus uncinata), via Wikimedia Commons

Pinus uncinata forests form habitats that favor the growth of a community of plants and animals, as is the case of the grouse. It is very sensitive to environmental changes; the increase in temperature and the alterations in the rainy seasons have a notable impact on its development and distribution.

It is a slow growing species, but it is very long-lived. Specimens can be found over 400 years old, although after 120 years they begin to lose their ability to reproduce.

characteristics

Size

This species grows to a height between 12 and 20 meters. Its trunk measures 0.5 to 1 meter. It is straight, growing erect, column-shaped. It has an ovoid-conical crown.

Cortex

The bark is thick at the base of the tree and its color is grayish. It is divided into several angular squamous plates.

Leaf buds and buds

They are uninodal, with shades ranging from gray to dark red. The buds are reddish brown, measuring between 6 and 9 mm in length. They are resinous and ovoid-conical in shape.

Leaves

These organs of the plant are born in fascicles of two, although sometimes they can be found, around the apex buds, in groups of three. Its color is green, being in dark and bright tones. The growth is in a straight line, with a slight twist.

They measure between 23 and 75 mm long by 0.9 or 2.1 mm thick. They have a gray foliar sheath, which persists between 4 to 9 years on the tree.

The leaves form a dense, dark foliage from which it derives its name: black pine. The cup is shaped like a cone or pyramid, which allows you to avoid damage caused by the weight of snow or strong winds.

Cones

The pollen cones are about 10 millimeters long and are yellow or reddish in color. The pollen contained in them is released in the months of May to July.

The cones where the seeds are found, once ripe, are dark brown. They are asymmetrical, having a length between 25 and 60 mm, and a width of 20 to 40 mm. These can be detached from the tree after the seeds are released.

Seeds

These reproductive structures are black, and may have stripes of the same color but in a more intense tonality. The body measures between 3 and 4 mm, and the wing about 7 or 12 mm.

Distribution

The Pinus uncinata species is native to Europe. It can develop in areas with elevations between 1000 and 2300 meters above sea level. Occasionally they could be found both at 200 meters above sea level, and in areas covered with ice, the limit of its resistance to cold being -23.3 ° C.

It is naturally found in the central and western part of the Alps. On the Iberian Peninsula they are located in the Pyrenees, from the Navarro de Roncal Valley to the Girona area. They can also be located in some mountainous areas of the Iberian system, whose altitudes are between 1500 and 2000 m.

There are also cultivated areas of black pine. These are found in the Sierra Nevada, a mountainous massif that belongs to the Betic mountain range, and in the Sierra de los Filabres, in the Spanish province of Almería.

In addition, they are also distributed in the Sierra de Guadarrama, which is made up of an Iberian mountain group.

In central France there is an isolated population of black pine that was introduced by man during the 19th century. Thanks to reforestation programs, large tracts of Pinus uncinata have been planted in the Mediterranean and northern Europe.

Habitat

The species known as black pine can adapt to the cold and dry air of mountainous areas. In these regions it grows forming pure forests, although it can also be found coexisting with other plant species. When mixed with other trees in the same habitat, the black pine is often the dominant species.

When it is found in the lower elevations, they are usually mixed with Pinus sylvestris and spruce. Towards the Atlantic areas they are joined by birch trees (Betula pendula Roth. And Betula pubescens Ehrh.)

If they are open regions or where they have undergone modifications that create clearings in the terrain, they can be found together with rowan (Sorbus aucuparia L.). In addition, they can also form wooded clusters with species of rhododendrons, creeping junipers and lingonberries.

The Pyrenees region

The Pinus uncinata can develop on slopes with rocky ground, in crevices and even in peat bogs. In the Pyrenees it can be found in four natural habitats:

• Subalpine and mountainous black pine forests. Here the vegetation is typical of the subalpine scrub, with the composition of an understory. You can also find the so-called "alpinized pastures".
• Black pine forests with rhododendron. This has a developed shrub layer that has an excellent regeneration.
• Acidophilic and xerophilous black pine forests. They are not very dense and have a very low capacity to regenerate.
• Calcareous and xerophilous black pine forests. These are very unstructured and regenerate slowly.
• Calcareous and mesophilic black pine forests. They have very little shrub layer, with some varieties of grasses.

Nutrition

Black pines are autotrophic beings, that is, they are capable of producing their own food. They do this thanks to the photosynthesis process that takes place in their leaves. Nutrition comprises the following processes:

Absorption

The tree takes substances such as water and mineral salts from the ground using its roots. The root system of Pinus uncinata is made up of a large number of short and thick lateral roots.

They spread and branch, frequently penetrating the cracks in the rocks where it lives. The mixture of water and mineral salts forms the raw sap.

Photosynthesis

In photosynthesis, the plant takes raw sap and carbon dioxide from the surrounding environment and, using the energy from sunlight, transforms them into glucose and oxygen, which is released into the environment. The final product is the processed sap.

This process occurs in the thylakoid membranes of the chloroplast. These membranes are formed by multiprotein complexes that participate in capturing sunlight and in photosynthetic electron transport. The efficiency of photosynthesis is influenced by the presence of light-harvesting proteins.

In recent research, it has been observed that conifers, a group to which Pinus uncinata belongs, lack two light-absorbing proteins (Lhcb6 and Lhcb3). These are present in the rest of the plant groups.

Scientific work maintains that the proteins Lhcb6 and Lhcb3 are not found in the gymnosperm genera Picea, Pinus (family Pinaceae) and Gnetum (Gnetales). This opens the way to future research to establish the advantage that this protein absence brings to conifers.

Transport

The plant consists of a system of woody vessels that transport the substances throughout the plant. The xylem is in charge of carrying water and mineral salts (raw sap) from the root to the other parts of the plant.

The phloem carries the processed sap, where the glucose molecules are. These are the main source of energy for plants.

Reproduction

Reproductive structures

The Pinus uncinata species produces specific structures for its reproduction, known as cones. There are male cones and female cones, both are found in the same tree, typical of monoecious plants, but in different branches.

Male cones

Male cones are small and have microsporophilic, scale-shaped modified leaves. In each of these there are two pollen sacs, known as microsporangia.

In these sacs the cell division known as meiosis occurs, which originates the pollen grains that will be released when they are mature. Pollen has two vesicles that evacuate towards the walls. These are filled with air, being able to facilitate their transport through the environment, due to the action of the wind.

Female cones

The female cones are produced during the winter, to develop and be mature in the spring, where pollination will occur.

This structure has a central axis with scales, arranged in a spiral. These scales can be tectric and ovuliferal. Each of the latter has, in the upper part, two ovules or megasporangia.

The ovum is made up of a mass of nucellar tissue and is surrounded by an integument. The micropylar end is oriented towards the central axis of the ovule.

In the megasporic cell, meiosis occurs, thus forming four megaspores, of which three degenerate. The functional megaspore increases in size, occupying a large part of the nucela.

Pollination

The pollen located in the male cones is transferred to the megaspore thanks to the wind and by the action of insects, which carry them attached to their legs.

During pollination, the megaspore exudes a sticky liquid called a pollination drop, whose function is to trap the pollen and direct it to the ovule.

The seeds begin to form, when they reach maturity, the cones open and the seeds come out. Some fall to the ground and germinate, while others are ingested by animals.

These, when defecating, expel the seeds in other areas spreading. Those that are trapped in the cone, come out of it when it falls to the ground or when it is moved by an animal.

Applications

Its wood is compact, presenting a fine grain. This allows it to be easily worked, making the final product of good quality. It is used in the construction area, in carpentry and as a combustible material.

In the Pyrenees, where large areas of this tree are found, its wood is used by artisans in turning, to build musical instruments and make small pieces of carpentry.

The properties of the Pinus uncinata wood are known to the timber industry. However, the majority of the general and specialized public, such as architects and builders, are unaware of the advantages of its use.

References

1. The Gymnosperm Database (2017). Pinus mugo subsp. Uncinata. Recovered from conifers.org.
2. Center tecnologic forestry of Catalunya, Office National des forets, Parc Naturel Regional des pyrennees catalanes et al. (Center regional de la propriete forestiere languedoc-roussillon, generalitat de Catalunya, geie forespir). (2012). Silviculture guide for black pine in the Pyrenees. Projet POCTEFA. Recovered from fidbosc.ctfc.cat.
3. American conifer society (2018). Pinus uncinata. Recovered from conifersociety.org.
4. Arbolapp (2018). Pinus uncinata. Recovered from arbolapp.es.
5. Roman Kouřil, Lukáš Nosek, Jan Bartoš, Egbert J. Boekema, Petr Ilík (2016). Evolutionary loss of light-harvesting proteins Lhcb6 and Lhcb3 in major land plant groups - break-up of current dogma. Reserch gate. Recovered from resergate.com.