THE CHANGES IN MANAGED FIR FOREST IN BESKID MTS DUE TO FOREST MANAGEMENT AFTER 11 YEARS

New phytosociological studies on permanent study plot (40 ´ 40 m) divided into 16 subplots in the managed forest were conducted in the upper part of basin of Bys trzanka (Beskid Niski Mts, SE Poland). The aim of the research was to determine the direction of changes in the Rubus hirtus-Abies alba community in the vicinity of the forest where forest management treatments are applied. It was recorded that the total number of species increased from 52 in 2000 to 80 in 2011. The DCA showed significant changes in species composition and the cover of species. Among others, the increase of forest edge species (epilobisation) and ruderal species (therophytization) and first of all the increase of meadow was observed. The structure of the community also changed; the mean cover of shrub species decreased.


INTRODUCTION
Forest management through timber exploitation, cultivation, silvopastoral system and even some methods of protection leads to changes in the structure and functioning of forest ecosystems. These changes also occur in the vicinity of sites where forest treatments are performed. Some forest treatments are applied in nature reserves as well. The cessation of any forest management practices mainly results in regeneration of forest phytocoenoses, increase of species richness, changes in proportion of ecological groups of species. There is a rich literature body on temporal changes in forests under protection [6,8,12]. Smaller number of publications are devoted to changes in managed and disturbed forests, in phytocoenoses difficult to classify in terms of syntaxonomical affiliation. Our study concern changes in managed forest exempli-fied by plant community in the Beskid Niski in southern Poland.
The main goal of the study was to examine modifications in the structure, species richness and species composition of the permanent study plot after 11 years.

METHODS
In the study methods used in work by Dubiel et al. [5] were applied on the formerly placed the study plot which was marked in the field. The study plot was prevented from any human interference i.e. no direct forest management treatments were applied including clear-cutting, thinning, cultivation of trees etc. The plot is of quadrate size with a side of 40 m and is divided into 16 smaller subplots (10Í10 m). In each subplot the phytosociological relevè was taken according to commonly applied Braun-Blanquet approach. Moreover, bryophyte species were inventoried. In order to examine the gradient of variation in species composition and the cover of plants between the 2000 and 2011 Detrended Correspondence Analysis (DCA) was done. To examine differentiation of species composition and the cover of species between the years eigenvalues (plot scores) along two first DCA axes were compared in terms of mean and range. The number of species (S), Shannon-Wiener index (H') and evenness index (E) as well as structure of phtocenosis (cover of tree layer, shrub layer, herb layer and moss layer) were compared between the years by means of Wilcoxon matched pair test. The G-test was applied to compare the proportions of species between the years. The simplified synoptic table with mean ±SD cover as well as the frequency (number of subplots occupied by a species) of all recorded species in 2000 and 2011 were given. Nomenclature follows Mirek et al. [14], Matuszkiewicz [13], Klama [9] and Ochyra et.al. [15].

RESULTS
The DCA results indicated a great differentiation in the vegetation after 11 years (Fig. 1), however, the two first axes explained only 20.4% of variation in species data. All species with their mean and SD of percent cover are given in table 1  (* -p < 0.05, NS -non-significant)

DISCUSSION
The comparison of species composition after 11 years demonstrated considerable changes. As in other floristic studies conducted mainly in forest reserves of Poland [4,20,7] the increase of total number of species occurred. Among others, species of forest fringe and non-woodland habitats including invasive plants as Solidago gigantea appeared. This species was recorded only in one subplot but its appearance indicates increasing disturbance of the forest floor. In many cases the increase in species richness is a result of the penetration of invasive alien species into plant community [8,12,20] which their abundance is higher, however, some studies show that the proportion of alien species amongst new species is relatively small [7].
In our study generally native species are newcomers but majority of them are non-woodland species. One possible reason could be another time of vegetation sampling. In a previous study [5] phytosociological relevés were taken in mid September and for this reason the authors stated that probably 1-2 species could be omitted. Taking into account which species were new in 2011 (study at the beginning of July) it cannot be confirmed that early spring species were  (Fig. 2). and higher availability of light at forest bottom.
Analyzing changes in species composition some degeneration forms of forest community can be distinguished [11,16].
The fringe species which occurred as Chamaenerion angustifolium, Geranium robertianum are plants known as indicators of epilobisation [3] and therophytization sensu Krotoska et al. [10] instead of therophytization as a massive occurrence of therophytes sensu Barbero et al. [1].
These species are neither frequent nor abundant, however, they are common in the vicinity of the study plot. Such high differences both in species composition, number of species and structure of phytocoenosis may be the result of forest management practices, which were conducted in the vicinity of the study plot. These were thinning of tree stand, clear-cutting and earth works. Moreover, the analysis of the map made by authors of the former work [5] and the comparison with the present state indicated that, according to hydrographic conditions, the area underwent profound changes. The changes in ephemeral water courses could result in the decline of tree stand which is mainly composed of fir Abies alba. At present, much lower seedlings of Abies alba were observed in comparison to 2000 (Tab. 1).
The increased cover of herbaceous non-woodland species could have hampered the development of young fir individuals. Bomanowska and Kiedrzyński [2] in their review work emphasize that the directions and range of dynamic changes in plant cover including forests are similar across the country and regeneration mainly occurs in protected forest areas where use is limited or has completely ceased. We believe that the cessation of all forest management treatments, not only within the study plot but in neighbourhood, might give the opportunity to study direction and rate of regeneration of forest community. In turn, this could bring profits both for nature conservation practice and knowledge about the succession of forest communities.