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Many studies on the changes in the rhythm of nature (animate and inanimate) revealed that plants are good indicators of climate change, because they are responsive to air temperature variations. There is a clear trend towards earlier onset of plant development in Poland, especially for spring phenological events as flowering and leafing. The main objective of this study was to identify phenological tendencies of selected plant indicator species in Poland and to explore the statistical relationship between mean phenological onset date against mean monthly air temperature. Phenological observations of 9 plant species: Corylus avellana L., Tussilago farfara L., Padus avium L., Taraxacum officinale F.H. Wiggers coll., Betula pendula Roth, Syringa vulgaris L., Aesculus hippocastanum L., Robinia pseudoacacia L., Tilia cordata Mill. from 25 locations acquired in the period 1951–1990 were used. The results proved that phenological changes were the reaction of plants to air temperature variations. For spring and summer phenophases, the mean correlation coefficient was negative — higher air temperature was related to earlier onset dates. The advance of spring and summer phenology was estimated at -2.2 days per 1°C. Majority of phenological events were the most significantly correlated with mean monthly air temperature of the preceding months. Phenological trends observed in Poland were mainly negative (73% of analysed stations), significant (22%) but diversified between the selected species. Linear regression analysis of the onset dates against year (including regression coefficient) showed the highest values for Corylus avellana flowering: -0.24 days per year (20% significant) and Betula pendula leaf unfolding: -0.18 days per year (33% significant). Robinia pseudoacacia showed significant advances (72% of negative trends were significant) in a summer season with an average rate of -0.3 days per year. Whereas in case of Tilia cordata no tendencies to advance has been proved.
Content available remote Post-fire changes of soil seed banks in the Elary succesionsl stage of pine forest
Our research was conducted on abandoned fields which had been undergoing spontaneous succession for 40–50 years and then were partly burnt. The main objective of the study was to examine if spontaneous fire in the early successional stage of pine forest causes a decrease in the number of species, diversity and density of seed banks, and an increase in the share of species forming long term persistent seed banks. Standing vegetation and soil seed banks were studied on 20 permanent plots on adjacent burnt and unburnt sites one and twelve years after spontaneous fire. One year after the fire the number of species in the seed banks of both areas was similar (11 and 12 species). In the burnt area the Shannon index and the floristical similarity between the seed bank and standing vegetation were lower, and seed density five times higher than in the unburnt area (15 691.5 m-2 vs.3426.5 m-2). This was mainly the effect of the high number of seedlings of Calluna vulgaris (L.) Hull and Spergula morisonii Boreau germinating from the burnt plots. Twelve years after the fire the number of species in both seed banks had increased little, but seed density in the burnt area (1742.5 m-2) had decreased 16 times, while that of the unburnt area had changed only slightly (2875.5 m-2). At the same time the Shannon index for the burnt area increased considerably, whereas for the unburnt one it did not change. Our study shows that the long-term persistent soil seed bank plays a fundamental role at the beginning of the post-fire regeneration of temperate coniferous forest vegetation. Germination of Calluna seedlings from the burnt soil seed banks in several times higher numbers than from unburnt soil seed banks may suggest that heat from the fire promotes a loss of dormancy in the heather seeds.
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.
Content available remote Small scale spatial pattern of a soil seed bank in an old-growth deciduous forest
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 x 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 dm[^3] and 0.159 m[^2]. 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 x 10[^3] seeds m[^-2] in upper soil layer and 3.00 x 10[^3] 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.
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