Janusz B. Faliński

UPROOTED TREES, THEIR DISTRIBUTION AND INFLUENCE IN THE PRIMEVAL FOREST BIOTOPE* **

The paper reports results of a long-term (1964–1974) investigation on permanent study sites in natural forest ecosystems of the Tilio-Carpinetum and the Pino-Quercetum in the Bialowieza Forest. The influence of decaying logs and root craters was investigated. It was found that the main causes of uprooting were the spring and autumn winds. Wind direction and the position of logs lying on the ground are correlated. Picea is most susceptible to uprooting by winds. Almost one half of the trees of this species are alive at the moment of uprooting. By mapping changes in the distribution of uprooted trees on a permanent area in time, a balance of the change over in a 10-year period was determined. It appeared that the decomposition is slower than accumulation. From this, it was concluded that the stand is in a phase of natural thinning. In the study site, compartments were disinguished with various degrees of change in the number of uprooted trees, and the consequences of differentiation and constant transformation of the biotope and biocenosis by the occurrence of uprooted trees and by their decay are described.

Vegetation Dynamics and Sex Structure of the Populations of Pioneer Dioecious Woody Plants

In connection with vegetation succession in old farmland and meadows, changes in the sex structure were analysed, particularly the sex ratio in populations, of Juniperus communis, Populus tremula, Salix aurita, S. caprea, S. rosmarinifolia, S. pentandra ete. Particular attention was given to the changes in the characteristics of Juniperus communis populations, associated with succession in old fields, leading from the segetal community Teesdaleo-Arnoseridetum, through the therophyte communities with Corynephorus canescens, lichens Cornicularlo-Cladonietum mitis, sand sward with the alliance Koelerion glaucae to Juniperus-Populus brushwood and Peucedano-Pinetum typicum forest. The particular succession phases over 70 yr and the phases of development of the pioneer populations of tree species were dated by the dondro-chronological methods. It was found that in the course of the succession the sex structure, and in particular the sex ratio, changes in the populations of the above-mentioned species. Among the factors that affect the natural populations, the increase in density of the Juniperus communis population itself together with changes in the structure of the whole associated community played the most important role. This factor inhibits growth of juniper individuals very strongly and retards the beginning of the generative reproduction phase of a given population by 10–15 yr. A hypothesis is advanced concerning the role of dioecism in pioneer tree species in the process of colonisation. In view of the changes in sex ratio in the population in connection with vegetation dynamics, at least two groups can be distinguished among the pioneer woody species: (1) Juniperus communis and Salix pentandra in which the sex ratio changes from prevalence of male individuals in the early phases of population (and vegetation) development to an equilibrium in the phase of stabilisation and to a greater or smaller numerical dominance of female individuals/in the latest phases; (2) Salix caprea, S. aurita, S. einerea and Salix rosmarinifolia and their hybrids, the populations of which are characterised by a constant prevalence of female individuals, but the sex ratio in the early phases of population (and vegetation) development reveals a higher contribution of male individuals. Juniperus communis and Salix pentandra in which the sex ratio changes from prevalence of male individuals in the early phases of population (and vegetation) development to an equilibrium in the phase of stabilisation and to a greater or smaller numerical dominance of female individuals/in the latest phases; Salix caprea, S. aurita, S. einerea and Salix rosmarinifolia and their hybrids, the populations of which are characterised by a constant prevalence of female individuals, but the sex ratio in the early phases of population (and vegetation) development reveals a higher contribution of male individuals.

Succession, regeneration and fluctuation in the Białowieża forest (NE poland)

A general description is given of the most important processes occurring in forest communities and of the spatial range and duration of the cycles of particular processes.

Androgyny of individuals and polygamy in populations of Salix myrsinifolia Salisb. in the south-western part of its geographical range (NE-Poland)

Abstract The aims of the study were to describe the phenomenon of androgyny (a change in the sexual behaviour of individuals) in Salix myrsinifolia, and to consider the implications of androgyny for the sex structure of local populations and for the sex structure of the species across a larger geographical range. Field surveys of the sexual behaviour of individuals and populations of Salix myrsinifolia were carried out over nine years (1989–1997) in an area of 40,000 km2 of NE-Poland. More detailed studies were performed on populations in Polana Bialowieska (the Bialowieza Clearing) in the Bialowieza Primeval Forest, in the Bialystok area, in the Biebrza Valley and in the experimental garden and laboratory of the Bialowieza Geobotanical Station. The bisexuality of Salix myrsinifolia is basically expressed through the development of a number of different forms of catkin that are intermediate between those that are entirely male and those that are entirely female. Flowers on bisexual catkins are fully developed, as on monosexual ones, but the male segment usually develops prior to the female one. With the exception of one form, a clear partitioning between the male and female parts of the catkin remains. This partitioning of the genders mainly takes place transversely, but in one case longitudinally. It is thus usually possible to speak of the division of a bisexual catkin into male and female sectors. In all three populations studied in detail, marked shrubs, on which bisexuality had been noted at the beginning, retained this trait throughout the 9-year observation period. However, there were changes in both the expression of bisexuality, i.e. the frequency of bisexual and monosexual catkins, and in the frequency of different patterns of bisexual catkin. Only bisexual individuals with a clear prevalence of female features retained their character. In the two larger populations studied, many originally monosexual individuals became bisexual during the study period. In the south-western part of the range of S. myrsinifolia in NE-Poland all local populations were characterized by the presence of bisexual individuals and are thus polygamous. There was a close association between the presence of S. myrsinifolia and the degree of ruderalization of habitats. The degree of polygamy in a population was also significantly correlated with ruderalization. It is concluded that androgyny and polygamy may be favoured not only by changes in environmental conditions, but also by the particular pressures to which individuals and populations of a species may be subject at the edge of its geographical range.

Dynamics of Salix caprea L. populations during forest regeneration after strong herbivore pressure

Broadleaved forest communities degenerated through strong pressure from large herbivores. Relief of this pressure led to regeneration, in particular of Salix caprea and other light-seeded pioneer trees: Populus tremula, Betula pendula and B. pubescens. This regeneration proceeded fol- lowing conservation protection of degenerate stands in a na- ture reserve and later in Bialowie2a National Park. The emer- gence and development of the Salix caprea population pro- ceeded following the expansion of Picea abies, which coin- cided with the period of enhanced animal pressure on the broadleaved forest. Salix caprea filled all the gaps in the tree stand after the destruction of trees and undergrowth by herbiv- ores (in the years 1892- 1915). The species also appeared abundantly in old, at the time unforested, clearings and felled areas. Here, S. caprea developed large populations with certain trees in good condition, with a growth form typical of forest trees and attaining considerable heights. The majority of trees were 50 - 60 yr old at the time of death, although some individuals reached 74 yr of age. The process of extinction of the Salix population - observed over 19 yr on permanent plots with marked trees - proceeded very quickly, especially in the first decade of observation. It led to the almost complete disappearance of S. caprea from the forest communities of Bialowie2a National Park. The death of individual trees is

The Bia3owie¿a forest, a relict ecosystem in Poland and Belarus

ABSTRACT The Bia3owie¿a Forest, a lowland area located along the border of Poland and Belarus, is a remnant of an extensive, larger forested region that once covered east-central Europe. In the 1400s the forest was set up as a separate administrative unit, a decision that has had long-term consequences for its preservation. Over the past 600 years the natural uniqueness of this ecosystem has been brought into sharp relief. Above all the Bia3owie¿a Forest stands out for the dominance of broadleaved and mixed coniferous stands, some of them in a near-primeval state. These stands are highly diversified with respect to age structure, canopy layers and species structure. There is an abundance of old trees and a wealth of other species, particularly spore-bearing flora and invertebrates that utilize wind-thrown or otherwise fallen trees and their decaying elements. The abundance and richness of ground vegetation, fungi, insects and microorganisms has resulted in a highly biodiverse ecosystem. The Bia3owie¿a area is also a refuge for Europes greatest assemblage of large herbivores, including Moose, Red Deer, Roe Deer, Wild Boar, and European Bison. It is also the site of Polands first National Park and three leading scientific institutions.