Search

Seedling emergence from soil seed bank was studied during 3 growing seasons 1997-1999 in: 1) 60 plots in 3 parts of the Potentillo albae-Quercetum patch: A - with Carpinus betulus (hornbeam) present only in the herb layer (canopy cover ca. 50-60%), B - after tree felling, at present with hornbeam dominating the shrub layer (cover > 90%), C - invaded by hornbeam 30-40 years ago (cover ca. 90%), and in 2) 60 soil samples from objects A, B, C kept in an unheated glasshouse. The results suggest that the seed bank realised in natural conditions is poorer in species with high light requirements (the Ellenberg indicator values for light (L ≥ 6) and their seedlings in comparison with the potential seed bank estimated in glasshouse conditions (field: A- 24; B - 17; C- 7, glasshouse : 44; 38; 32 species / 2 m2, field: 321; 108; 14, glasshouse: 785; 1205; 177 seedlings / m2, respectively). Contrarily, more species and seedlings with moderate light demand (L = 3-5) appeared in the field plots (field: A- 26; B- 25, glasshouse: 20; 14 species / 2 m2, field: 1014; 310, glasshouse: 328; 71 seedlings / m2). The shading by hornbeam negatively influences the size of the seed bank (field: A - 1743; B - 1226; C - 680, glasshouse: 1547; 3274; 459 seedlings / m2) and its species richness (field: A- 55; B - 48; C - 19, glasshouse: 76; 59; 56 taxa / 2 m2). Nomenclature: syntaxa - Matuszkiewicz (1981), taxa - Mirek et al. (1995).

The research was conducted on four patches of thermophilous oak wood in Białowieża Primeval Forest: A – with a woodstand: oak + approx. 30-year-old hornbeam + hornbeam brushwood; B – with a hornbeam stand formed by natural seed fall after logging (ca. 1920) oaks; C – after logging oaks and replanted (ca. 1965) with pine and oak; D – with a natural low-density oak stand. Species composition and seed bank density were estimated using the seedling emergence method. Seedling emergence was observed over two vegetation seasons. Research demonstrated that: 1) the species abundance of the seed banks depends on canopy cover (A, B approx. 50 species; C, D approx. 70 species); 2) the floristical similarity (Sørensen's index) of the seed bank and ground vegetation is higher in the undisturbed patch D (0.50) than in disturbed patches (0.30-0.35); 3) species diversity in plots A, B, C, D (H'=12.5; 13.4; 15.5; 16.9) and seed bank density per m2 (432.5; 958.0; 1486.5; 2268.0) are negatively correlated with the degree of patch shading; 4) the average weight of diaspores in the seed banks of shady plots is lower (A, B approx. 0.003 g) than that of sunny plots (C, D approx. 0.08 g); 5) the share of long-lived diaspores increases in patches after logging.

Atriplex tatarica is an invasive annual plant from Central Asia. It is an early successional species of disturbed habitats, tolerant of a high content of NaCl. It grows also by the roadsides, on lawns by the streets and other places in cities sprayed with salt during snowfalls. The paper presents results of the analysis of abundance and patterns of occurrence of this invasive subhalophytic plant by the roadsides in the Warsaw city. We found that frequency and distribution of Atriplex tatarica increased significantly over the last few decades. The species grows chiefly along main streets which are de-iced. It forms monodominant patches of different length at the zone closest to the street verge. The NaCl concentration there is significantly higher than in the zones more distant from the street verge, although this parameter is very variable. The cover of other species increases with an increasing distance from the roadside verge.