Taxonomy Of The Genus Picea

The genus spruce (Picea A. DIETR.) belongs to the family Pinaceae, which includes other key taxa of conifers such as pine, fir, and larch. The Pinaceae family is divided into the following three subfamilies: Pinoideae, which includes the genus Pinus only; Laricoideae, with the genera Larix, Cedrus, and Pseudolarix; and Abietoideae, including the genera Abies, Picea, Pseudotsuga, Tsuga, and others. The absence of dwarf shoots is characteristic of the subfamily Abietoideae in which the needles are arranged only on long shoots. In contrast, in the subfamily Pinoideae, needles occur only on dwarf shoots except for the juvenile primary needles of the seedlings. The subfamily Laricoideae exhibits needles on both long and dwarf shoots.

CARL Linné (1753) included all taxa of the Pinaceae family, the pines, firs, and spruces in the same genus Pinus. He named the two spruce species known at the middle of XVIII century, Norway spruce - Pinus abies L. and Caucasian spruce - Pinus orientalis L. The Linnean name "abies" is valid as the oldest one, according to International Code of Botanical Nomenclature (GREUTER 1994). Consequently, the accepted name of Norway spruce is Picea abies (L.) KARST., replacing a long-used name P. excelsa LINK (1841, after VOGELLEHNER 1977). The latter binomial was derived from Pinus excelsa Lamarc (1778, after VOGELLEHNER 1977). The name Picea abies was described and used first by KARSTEN in 1881 (VOGELLEHNER 1977). The genus Picea was described and separated from the Linnean genus Pinus by A. DIETRICH in 1824, who described Norway spruce under the name Picea rubra A. DIETR. (VOGELLEHNER 1977).

Of the several dozen species that belong to the genus Picea, many are important forest trees. The exact number of species has been difficult to ascertain, owing to the fact that the spruces are highly variable and frequently form intermediate taxa, possibly of hybrid origin in areas where two or more species occur together. Avery high level of intraspecific variation is also characteristic of Picea abies.

Linné (1753) recognized and described only two species of spruce. The number of recognized species in the genus has grown with the time, as a result of new discoveries, especially in North America and eastern Asia. Many new species were first described near the end of the 19th and beginning of the 20th centuries. The numbers of species noted in the seminal taxonomic studies of the conifers in the 20th century vary between 24 and 49 (for details see: MAYR 1906; BEISSNER 1909; FITSCHEN 1930; LACASSAGNE 1934; GAUSSEN 1966; Harrison and Dallimore 1966; Bobrov 1970; Krussmann 1972; Schmidt-Vogt 1974; PRAVDIN 1975; REHDER 1977; VOGELLEHNER 1977; Alden 1987; Farjon 1990; TAYLOR 1993; FARJON 2001; Weng and JACKSON 2000).

The most recent taxonomic monographs of Picea divide the genus into three sections (e.g. GAUSSEN 1966; Bobrov 1970; REHDER 1977; VOGEL-LEHNER 1977; Alden 1987). Alternatively, a more recent classification divides the genus into two sections of two subsections each (FARJON 1990).

Section 1. Picea (=Eupicea WiLLK.)

The needles are regularly quadricular in cross-section, frequently almost rhomboidal. The stomata are dispersed regularly along the entire four surfaces of the needle. The cone scales are hard, lignified, and more or less rounded on top. To this section belong Picea abies s. l. (including P. obovata), P. orientalis, many Asiatic species, as for example, P. asperata MAST., P. neoveitchi MAST., P. wilsonii MAST., P. polita CARR., P. maximowiczii REG., P. bicolor MAYR, P. glehnii MAST., and P. koyamai SHIR. and several North American spruces, such as P. glauca VOSS, P. mariana Britt., and P. rubens SARG.

Section 2. Casicta MAYR

The needles are irregularly quadricular in cross-section or flattened with stomata present on all four surfaces or only on the lower surface in in taxa exhibiting a flattened needle morphology. The cone scales are slender, flexible, with undulate margins, and loosely arranged. To this section belong the species present in North America, such as Picea sitchensis CARR., P. pungens ENGELM. and P. engelmannii ENGELM., and from North-East Asia, the species P. jezoensis CARR. and P. likiangensis E. PRITZ.

Section 3. Omorika WILLK.

The needles are flattened, dark green on the upper surface, with white or bluish-white rows of stomata on the lower side. The cone scales are closely adherent, thick, inflexible, and rounded. The Picea omorika PURK. in Europe and P. breweriana Wats. in North America and a few other species from eastern and central Asia belong to this section.

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