Page 31 - Наукові записки Державного природознавчого музею, 2022 Вип. 38

30 Кузярін О. Т, Любинець І. П., Хомин І. Г.

Kuzyarin O.T., Lyubynets I.P., Khomyn I.G.
Phytocenotic conditions and structure of the local population for Betula humilis Schrank
near Zhornyska village (Ukrainian Roztochchia)
Phytocoenotic conditions and structure of the local population for Betula humilis in the north-
eastern environs of the village Zhornyska, Yavoriv district, Lviv region, on the territory of the
Roztochchia International Biosphere Reserve have been studied. Four coenopopulations (CP) of
the species are confined to secondary plant communities of sicaciogenic and pyrogenic successions
with different sod levels of the peat soil, as well as missing or unequally expressed tree layer. The
least transformed communities with the dominance of B. humilis (40-80% p.c.) in the shrub layer
and no stands in terms of floristic composition and spatial structure correspond to the derived
mesohygrophytic and hygromesophytic variants of the association Betuletum humilis Steffen 1931.
The most transformed areas with sparse tree layer are represented by pioneer forest communities
- birch woodlands. Seventy-five species of higher plants (seventy vascular plants and five
bryophytes) were found in the floristic composition of phytocenoses. The minimal participation of
helophytes and the presence of invasive species indicate a high level of mesophytization and
synanthropization of modern phytocenoses. Within the locality B. humilis forms different in area
and density of formation shoots (turions) of the colony-curtain mainly from semi-autonomous
2
subpartial bushes 0.3-2.2 m tall. The largest curtains (up to 300 m ) with a high density of living
2
formation shoots (up to 293 pcs/m ) are confined to open well-lit areas. The age of old skeletal axis,
not exceeding 9 years was determined and the annual growth of shoots has been calculated. The
parameters of seed productivity (SP) of the local population of B. humilis vary within: potential SP
- 89.48–109.24 seed germs, actual SP - 80.84–100.4 seeds. The coefficient of seed productivity is
quite high (86.69-92.16%) for all coenopopulations. Based on the results of research and analysis
of the literature the life form of B. humilis, which belongs to vegetatively mobile hypogeogenic-
geoxyl deciduous shrubs that form colonies or clones of (semi) autonomous (sub) partial (daughter)
shrubs and are characterized by monopodial-sympodial shoots growth has been clarified. The big
life cycle of the species characteristic of shrubs consists of development cycles for systems shoots
formation (main skeletal axes), which are successively replaced, and lasts for decades. The
development cycle of the system formation shoot covers the periods of intensive growth
(appearance of formation shoot from an additional or dormant bud in the first year), relative
stabilization of growth processes with the formation of first and higher-order branching shoots
(from second to tenth years) and ageing and death of shoots (after about ten years of age).
Key words: Betula humilis, habitat, phytocenotic conditions, coenopopulations, density of
formation shoots, annual growth of shoots, seed productivity, Ukrainian Roztochchia.