We studied an old growth deciduous forest seed bank to examine how its potential role in regeneration is shaped by natural forest environment. Our research questions were: is the spatial pattern of seed bank influenced by local variation in elevation, soil moisture and light intensity, and what is the impact of herb layer characteristics on seed bank pattern. We recorded species composition of the herb layer and seed bank on a 2 × 40 m study plot divided into 20 quadrates, situated in a natural oak-hornbeam forest, in the Białowieża Primeval Forest, (NE Poland). Soil cores were sampled from two soil layers (0–5 cm and 5–10 cm) yielding altogether 40 samples of a total 15.9 dm3 and 0.159 m². Seeds were extracted from soil samples under a microscope. Ellenberg indicator values were used to characterize light (L) and moisture (F) conditions. Relative quadrate elevation was averaged for nine points. There were 6.65 × 10³ seeds m⁻² in upper soil layer and 3.00 × 10³ seeds m⁻² in lower soil layer. Seed bank structure constituted of patches 6 m diameter in the upper soil layer and 4 m in the lower soil layer. Aggregated pattern of the seed bank was influenced by clumped distribution of plants in the herb layer. Seed bank species richness in the upper soil layer was correlated with moisture (r = 0.485, P =0.03) and light (r = 0.526, P = 0.0172) values. Seed densities were correlated with moisture (r = 0.848 P <0.0001 upper and r = 0.491 P = 0.0278 lower soil layer) and light (r = 0.803 P <0.0001 upper and r = 0.751 P = 0.0001 lower soil layer). Seed density in upper soil layer was negatively correlated with elevation (r =–0.485 P = 0.0422). Higher seed density and species richness of the seed bank associated with better light conditions and higher moisture is probably caused by higher seed production in favourable conditions, and factors promoting seed persistence in soil. Our results indicate, that even subtle changes in light, moisture and mean relative elevation can shape seed bank spatial pattern on a fine local scale, differentiating the response of this community to small scale disturbances present in natural forests.
Studies on the soil seed banks of fallow lands of different ages were carried out on poor soil abandoned fields and in a fresh coniferous forest in north-eastern Poland. The size and diversity of seed banks was studied with the seedling emergence method. Species abundance (i), density (ii), number of species from different biological groups (iii) and distribution and mean LI value (iv) were analysed as the function of fallow land age. It was found that: (i) species diversity, number of species and ln of density are linear declining function of the fallow land age; (ii) for approx. 25 years the share of diaspores of identified species groups has been relatively similar. Seed banks of 40-50-year-old fallow lands are dominated by Calluna vulgaris, while the seed bank of the old fresh coniferous forest is dominated by dicotyledonous perennials and grasses; (iii) within the first 50 years of succession the persistence of seed banks measured by the Longevity Index increases gradually.
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.
Thermophilous oak wood is the most species-rich forest habitat in the zone of mixed deciduous forests. A very limited amount of it has been saved in good condition. We investigated the principal hypothesis that the vegetation and seed banks, especially of the ancient forest species, are good indicators of habitat naturalness and its aptitude for restoration. Vegetation and seed bank sampling were carried out in fragments of forest with a known management and disturbance history over the past 80 years. We predicted that natural and anthropogenic transformations of tree stands would be significant factors shaping species composition and similarity of vegetation and seed banks. The closest similarity was observed between the seed banks of plots which were never logged. The least related to others was the seed bank of the logged site, whose soil was ploughed prior to tree replantation. The highest number of ancient forest species was recorded in the vegetation (33 species) and in the soil seed bank (21 species) of the least transformed patch of thermophilous oak forest. It was decreasing gradually with increase of the tree canopy cover on the research plots. Our results indicate also that the higher the coefficient of similarity between seed bank and vegetation, especially of the ancient forest species, the higher the forest’s naturalness. We conclude that restoration of thermophilous oak wood has the highest chances for success in patches with well preserved seed banks and vegetation.