Diagnostic Value of Selected Morphological Traits of (Betula Carpatica Waldst. Et Kit.)

1991

S. 27-37

24 Lit. Ang.

Unselbständiges Werk

200090660

Roczniki Akademii Rolniczej w Poznaniu. Lesnictwo ; 231,Nr. 29, S. 27-37

Betula carpatica Waldst. et Kit. is one of the most critical taxons among the Polish birch-trees. In plant systematics birch is regarded either as an independent species, or as a subspecies or variety of the widely understood species of Betula pubescens Ehrh. Difficulties in the determination of the taxonomic separateness of Betula carpatica, and in the definition of the intraspecific structure of Betula pubescens follow primarily from the lack of complex studies on these birches. The paper presents a summary of study results on the morphological variability of Betula carpatica in Poland. It analyses the variability in the traits of leaves, fruits, scales as well as the growth forms, length of dwarf shoots, pilosity of one-year-old twigs, colour of outer bark. The separateness of Betula carpatica in relation to Betula pubescens is expressed by the absence or a lesser intensity of pilosity of one-year-old twigs and leaves in vein angles, as well as by smaller dimensions of leaves, a smaller number of side vein pairs, by the fact that the side valves of scales are higher elevated towards the top, and on the average the wings are situated lower and they are narrower than the nut. The forms of the growth and colour of the outer bark are subject in a significant way to the modificational pression of environment and they cannot be regarded as traits characteristic of Betula carpatica. The present populations of Betula carpatica in Poland have a relict character. In the most typical form they have been preserved in the subalpean zone of the Tratra and Sudeten Mountains. Most probably they originate from the late- glacial period came into contact with Betula pubescens widely spread on the lowland, and in a lesser degree also with Betula pendula Ehrh. In results of crossing and introgression the variability character of these populations was shifted in the direction of Betula pubescens. In the preservation of the comparatively morphologically most different populations of Betula carpatica in high mountain localities, a deciding role was certainly played by the spatial isolation exerting a lesser influence in the lower mountain regions. These populations are best determined as Betula pubescens Ehrh. ssp. carpatica (Wild.) Ascherson et Graebner.