Pinus serotina in the United States Botanic Garden
Pinus serotina is an evergreen conifer from the genus of the pines ( Pinus ) with mostly 15 to 20 centimeters long, needles growing in groups of three or four and 6 to 10 centimeters long seed cones. The natural range is in the southeastern United States. The species is often assigned to the species Pinus rigida as a subspecies or variety , but its species status is mostly recognized. It is classified as not endangered inthe IUCN Red List . The species is used little economically and mainly for the production of pulp .
Pinus serotina grows as an evergreen tree up to 20 meters high. The trunk is straight or often crooked and reaches a diameter of 60 centimeters at chest height . The trunk bark is thick and breaks into dark reddish brown, irregularly rectangular, flat, but scaly plates that are separated by deep cracks. The main branches are horizontal or ascending, they are twisted, shorten only a little over time and form an irregular, thin crown. The needled branches are thick and few in number. Young shoots are about one centimeter thick, initially yellowish orange and often glaucous , later brown and covered with numerous buds. Often adventitious shoots are formed on the largest branches of the crown, more rarely on the trunk.
Buds and needles
The buds are narrowly ovate to cylindrical and very resinous. Terminal buds are 15 to 20 millimeters long. The lower leaves , formed as bud scales, are reddish-brown, pressed, edged and sharply pointed. The needles usually grow in threes, rarely in groups of four, in a basal needle sheath that is initially 20 to 25 millimeters long and shortens to 10 millimeters. Adventitious shoots have three to five needles per needle bundle. The needles are green, straight, flexible, slightly twisted, usually 15 to 20 centimeters, rarely from 13 to 21 centimeters long and 1.3 to 1.5 rarely up to 2 millimeters thick. They stay on the tree for two to three years. The edge of the needle is finely sawn, the end pointed. There are stomata lines on all needle sides .
Cones and seeds
The pollen cones grow spirally arranged in groups at the base of young shoots. They are yellowish brown, cylindrical and 2 to 3 inches long. The seed cones grow individually or in whorls of two to five, sitting or on stalks up to 1 centimeter long. The cones are closed ovoid-conical, symmetrical and from 5 usually 6 to 10 centimeters long. The cones open after two years or later if triggered by fire. They are broadly ovate to almost spherical when open, with a flattened base and a diameter of 8 centimeters. They remain on the tree for several years after the seeds have been released. The seed scales are thin, woody, elongated, stiff and dull brown with a red-brown edge strip. The apophysis is slightly raised, transversely keeled, more or less rhombic in outline, light brown or pale red-brown. The umbo is small, conical and usually reinforced with a short, weak spine , sometimes unarmed. The seeds are oblique ellipsoidal, slightly flattened, 5 to 6 millimeters long, pale brown and spotted dark brown. The seed wings are 15 to 20 millimeters long.
The number of chromosomes is 2n = 24.
Distribution, ecology and endangerment
The natural range of Pinus serotina is in the southeastern United States and ranges from New Jersey to Delaware , Georgia , Maryland , North Carolina , South Carolina and Virginia to Alabama and Florida .
The species grows in the damp, swampy lowlands on the Atlantic Ocean and the Gulf of Mexico from sea level to a height of 200 meters. The climate is mild and humid with an annual annual rainfall of 1120 to 1420 millimeters and the driest months in winter. The distribution area is assigned to winter hardiness zone 8 with mean annual minimum temperatures between -12.2 ° and -6.7 ° Celsius (10 to 20 ° Fahrenheit ). Pinus serotina often grows together with the bald cypress ( Taxodium distichum ), other pines such as Pinus taeda and Pinus elliottii and deciduous trees such as representatives of the tupelo trees ( Nyssa ) and magnolias ( Magnolia ), the tulip tree ( Liriodendron tulipifera ) and species from the genus Persea and the holly ( Ilex ). The species forms an open crown layer under which a dense undergrowth forms, which is characterized by the stinging windmill Smilax laurifolia . Their ability to sprout again distinguishes them from the similar species Pinus rigida , as they form the adventitious shoots more in the crown area than on the trunk. This is probably an adaptation, since in the humid environment fires are more likely to break out in the crown area.
Systematics and research history
Pinus serotina is a species from the genus of the pines ( Pinus ), in which it is assigned to the subgenus Pinus , Section Trifoliae and Subsection Australes . It was first scientifically described by André Michaux in Flora Boreali-Americana in 1803 . The generic name Pinus was already used by the Romans for several types of pine. The specific epithet serotina comes from Latin and means “late” or “coming late” and refers to the often late opening of the seed cones, which is only triggered by fire.
Pinus serotina forms natural hybrids with both Pinus rigida and Pinus taeda , but is usually viewed as a separate species. It is closely related to Pinus rigida , with which it shares the development of adventurous drives, but there are a number of differences, mostly only quantitative ones, that justify the species status. There are differences in the length of the needles and when the cones open. The area of distribution and ecology only overlap to a small extent. However, where there is overlap, such as in southern New Jersey and on the Delmarva Peninsula in Delaware and Maryland, there is a continuous transition between the two species. Therefore, the taxon was described both as a subspecies and as a variety of Pinus rigida , giving the synonyms Pinus rigida subsp. serotina (Michx.) RTClausen and Pinus rigida var. serotina (Michx.) Engelm.
The wood of Pinus serotina is coarse-pored and resinous and the trees only reach a small height, often have crooked trunks that split into long branches at two thirds of their full height. The wood is therefore mostly processed into pulp . The slow growth in the nutrient-poor, acidic and swampy environment make economic use less interesting. However, the species grows much better in plantations on well-drained, sandy soils. Attempts to use them for forestry in China (in Jiangsu , Jiangxi , Zhejiang provinces ), South Africa and Zimbabwe, but had less success than with other pine species.
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