Intraspecific Variation

Norway spruce exhibits considerable intraspecific variation. The number of described variants in morphology and physiology is the largest among the spruce species. There are about 140 known varieties and forms (cultivars) in addition to described wild types, which differ in cone dimensions or cone scale shape.

3.2.1. Norway spruce and Siberian spruce

One of the most important issues in Picea abies taxonomy is the relationship between Norway spruce and Siberian spruce. In 1833 LEDEBOUR described Siberian spruce as a separate species, P. obovata LEDEB. This classification is disputed, and it is unresolved whether P. obovata should be considered a separate species or only an intraspecific taxon within P. abies sensu lato. The main morphological characteristic distinguishing Picea obovata from P. abies sensu stricto is its comparatively small cone size (4-8 cm in length) and broad, rounded cone scales (Fig. 3.1). The cones of the typical P. abies are 10-15 cm long and are characterized by scales that are acute, denticulate, and somewhat flabellate and generally variable. For this reason many taxonomists consider P obovata a separate species (FITSCHEN1930; LACASSGNE1934; GAUSSEN1966; Harrison and Dallimore 1966; Krussmann 1972; Rehder 1977; Farjon 2001). Russian botanists also treated P. obovata as a separate species (Sukatchev 1928; Komarov 1934; VASILEV and UKHANOV 1949; BOBROV 1970; PRAVDIN1975). Comparing spruce cones from the Altay Mts in Asia and from the mountains of Europe, TEPLOUKHOV (1868) suggested that P. obovata should be considered a geographic variant of P. abies. Other taxonomists concur, and Siberian spruce is more recently treated as a subspecies or geographic variety of P. abies (l.) Karst. (SCHMUCKER 1942; LINDQUIST 1948; HULTEN 1949; Franco Amaral 1964; VOGELLEHNER 1977; Staszkiewicz 1977). In our taxonomic treatment in this volume, we consider Norway spruce as a species comprised of both P. abies and P. obovata sensu stricto. The latter taxon is treated as a subspecies of P. abies (after VOGELLEHNER 1977 and FARJON 1990):

Norway spruce - Picea abies (L.) Karst. subsp. abies

Synonyms: Pinus abies L. (1753), Abies picea MILL. (1768), Pinus picea DU ROI (1771), Pinus excelsa Lam. (1778), Picea rubra A. Dietr. (1824), Picea excelsa Link (1841), Picea alpestris BRUEGG ex STEIN (1887) Siberian spruce - Picea abies (L.) Karst. subsp. obovata (Ldb.) HULTEN

Synonyms: Picea obovata Ldb. (1833), P. abies var. obovata (LDB.) FELLM. (1869), Picea excelsa subsp. obovata (LDB.) ASCHERS. et GRAEBNER (1913), Picea abies var. arctica LINDQ. (1948).

An additional problem concerns the occurrence of Norway spruce specimens with the cones of the Picea obovata type in the mountains of central Eu-

Figure 3.1. Cones of Picea abies (photo E. Szubert)

A - subsp. abies; B - subsp. obovata rope (the Alps, Sudety, Carpathians). One explanation is that these cone characteristics are an adaptation to the high mountain climate conditions (VOGELLEHNER 1977). Another explanation is that populations growing at high altitudes in the mountains of Central Europe are relicts of past migrations of P. obovata (BOBROV 1978). During the Holocene this variety (P abies var. alpestris or, as other authors prefer, P. obovata var. alpestris) may have been replaced by spruce taxa from other glacial refugia with isolated populations surviving only in the highest altitudes, where gene flow took place between populations of European and Siberian origin (BOBROV 1978). The process of introgression is considered one reason for the large degree of variation of the species in Europe.

3.2.2. Natural varieties of Norway spruce

3.2.2.1. Cone variation

The great variation in shape and form of cones, and especially of cone scales, underpins the description of a dozen or so varieties and forms (SUKATCHEV 1923; PACZOSKI1925; TYSZKIEWICZ 1934a; MEZERA1939; LINDQUIST 1948; Korzeniewski 1953; Jurkevich and PARFENOV 1967; HOLUBCiK 1969a, b; Bobrov 1970; VOGELLEHNER1977). The following three taxa are accepted in recent taxonomical reviews of the species. Picea abies subsp. abies var. picea (=var. europaea TEPL.)

Cones are large, 10-18 cm long. Cone scales range from obovate to rhomboid in shape, flat to somewhat convex, margins lack serration, sometimes with two indentations and slightly flabellate on the top. Scales overlap each other by 2/3 - 3/4 in the cone. This variety predominates in the western Carpathians and Sudety Mts with a frequency of 80-90% (STASZKIEWICZ1977). Picea abies subsp. abies var. acuminata (Beck) Jurk. et PARF.

The cones are as large as in the previous variety, 10-18 cm long. The cone scales are slender and elongated (longer than wide), flabellate on the margins, and flexible on the somewhat ligulate tops, mostly adherent, but sometimes strongly reflexed (f. deflexa Tyszk.). The scales overlap to about ^ below each other in the cone. The variety acuminata occurs in populations from the eastern Carpathians and in southern part of the northeastern portion of the species range (JURKIEWICZ and PARFIENOW 1966). Picea abies var. alpestris (BRUEGG.) DOMIN

The cones are smaller, 6-12 cm long. The cone scales are deltoidal or spatulate, erect and wider than long, with rounded tops lacking flabellation and indentation or only slightly serrulate. The scales overlap by more than % inside each other. The cones of this variety are similar to those of P. abies subsp. obovata. Individuals with this cone form are present in the highest locales of the mountains of central Europe in the Alps, Sudety, and Carpathians.

Within the above-mentioned varieties a dozen or so forms have been described on the basis of detailed characteristics of the cone scales (MEZERA 1939; JURKIEWICZ and PARFIENOW 1966; HOLUBCiK 1969b; 1971, 1972). In general, these traits are highly variable and likely instable as a result of gene flow among varieties, and are not useful traits in taxonomic studies.

3.2.2.2. Macrostrobili variation

During pollen reception, the female strobili can have various colors. On this basis at least three forms can be distinguished:

- f. chlorocarpa PURK., with green strobili

- f. dichroa DOMIN, with reddish-green strobili

- f. erythrocarpa PURK., with red strobili

3.2.3. Cultivars

The great variability of Norway spruce in the wild and its propensity to form morphological variants has resulted in its extensive use in ornamental plantings. To date, about 150 such varieties have been described. Many were found in the wild, such as var. virgata or columnaris. Numerous dwarf varieties are often fixed teratological forms arising from witches' brooms. The cultivars of Picea abies subsp. abies are generally divided into three groups: tree-like forms, dwarf forms, and varicolored. Some differ from the typical Norway spruce in their ecological and physiological characteristics. For example, the dwarf forms are drought resistant and grow well on sandy soils. Below are mentioned some of the most commonly planted ornamental forms.

3.2.3.1. Habit cultivars

'Columnaris' - the columnar variety. A tree to 20 m in height, characterized by a narrow, dense crown, with short, dense, horizontally arranged branches. Under this name many various varieties can be found in parks and nurseries, originating from various mother plants taken from the forest.

'Cupressina' - the cypress variety. This variety is a tree-like form, attaining a height of about 10 m with a very regular, conical, and dense crown. The branches are upright and arranged on the trunk at an acute angle.

'Inversa' - the inversed variety. This is a slow-growing tree with an inclined trunk and highly elongated, pendent branches. Quite frequently it is procumbent. The growth habit is extremely variable, depending on the inclination of the trunk.

'Viminalis' - the sarmentous variety. This variety is frequent in the wild. The trees exhibit a typical excurrent crown form, attaining more than 20 m in height, and are characterizing by strong, widespread main branches, but flattened and pendulous secondary branches.

'Virgata' - the snake-like variety. Most often this variety is a small tree and rarely occurs as a shrub. Its loose crown is comprised of long (not ramified) snake-like, pendulous shoots. The needles are thick, rigid, and prickly, up to 3 cm long. It was isolated as a wild variety. Individuals occasionally produce cones and viable seed that may produce offspring comprised both normal and more or less 'virgate' individuals.

3.2.3.2. Dwarf varieties

'Barryi' - variety of BARRY. A small, slow-growing tree up to 2 m in height with a broad, conical or irregular crown. The apical shoots are thick and strongly sulcate. The branches are short and densely arranged on the trunk. Needles are short and obtuse.

'Clanbrassiliana' - variety of CLANBRASSIL. Discovered in Ireland in 1790, this is one of the oldest dwarf varieties. It is a low, slow-growing shrub, rarely taller than 1 m, with a dense, slightly flattened crown. It has short (to 1 cm long) needles that are densely arranged on the twig. Numerous dwarf forms are similar and known under the names of 'Pyramidalis Compacta', 'Pygmea' or 'Nana', for example.

'Merkii' - the MERK'S variety (Fig. 3.2). This variety is a stout shrub to about 3-4 m high with a broad, conical, and somewhat irregular crown. It forms numerous main, upright shoots, forming its characteristic crown shape in older individuals. The needles are thin and prickly and markedly shorter on the young shoots than on the older shoots.

'Nidiformis' - the nest form. This is a slow-growing shrub attaining a height of 1 m and characterized by a broad, dense, and flattened crown with a characteristic nest-like depression in the center. The branches form distinct annual whorls. This is a frequently planted variety.

Figure 3.2. Picea abies 'Merkii' in the Kornik Arboretum, Poland (photo E. Szubert)

'Procumbens' - the procumbent variety. This variety resembles the previous variety, but the crown is broader and more flattened. The lowest branches are suspended above the ground. The needles are arranged in a single plane and are of varying length with the longest needles in the central portion of the shoot.

'Pygmaea' - the dwarf variety. A shrub up to 80 cm tall, very slow-growing and densely branched, broadly conical or spherical. The shoots are lightly colored. The dark-green needles are 8-10 mm long. This form is frequently planted.

3.2.3.3. Color varieties

'Finedonensis' - the yellow-needle variety. This variety is a tree of normal growth habit, but slower growing. The needles on the new shoots in the spring initially appear light yellow in color, but become naturally green within two to three weeks. This is a highly decorative, ornamental variety.

Wladyslaw Bugala, Polish Academy of Sciences, Institute of Dendrology, Kornik.

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