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Too intensive management by mowing or grazing or cessation of management both lead to the floristic impoverishment of meadow communities. Soil seed bank can play an essential role in the ecological restoration of species-rich semi-natural grasslands. In Poland, little research has been conducted in this area, particularly refers to Arrhenatherion meadows. The aim of the studies was to determine the density and species composition of the soil seed bank of Arrhenatheretum elatioris meadows as well as the distribution of seeds across four soil levels. The studies were carried out in two habitats: Arrhenatheretum elatioris (code 6510-1) and Poa pratensis – Festuca rubra (code 6510-2). Soil samples were collected up to a depth of 20 cm, divided into four levels: 0-5 cm, 5-10 cm, 10-15 cm 15-20 cm. The size and species composition of the seed bank was determined by extracting seeds from the soil samples. The number of diaspores (seeds and fruits) in the topsoil (0-20 cm) layer was 56,430 seeds·mˉ² (Arrhenatheretum elatioris) and 118,510 seeds·mˉ² (Poa pratensis – Festuca rubra). The soil seed banks were dominated by diaspores of annual dicotyledonous species (above 80%) which were mainly seeds of arable weeds or ruderal plants. The assessed soil seed banks were dominated by Chenopodium album and Stellaria media. In both grasslands, the quantity of Poaceae and Fabaceae diaspores were very low. These results confirmed that most mesic grassland species did not form persistent seed banks and reintroduction of target species seeds is necessary in order to restore the species-rich Arrhenatherion elatioris meadows.
Heteromorphic achenes are formed within each capitulum of Galinsoga ciliata (Rafin) S.F. Blake. We examined (1) the effects of the duration of dry storage on germination and (2) the effect of burial in soil on viability and germination of heteromorphic diaspores. Fresh harvested peripheral achenes remained dormant, while central achenes germinated at 60%. Both achene types became non-dormant after one month of dry storage. In successive months of dry storage, peripheral achenes demonstrated a higher germination percentage than central achenes. The peripheral and central achenes showed similar temperature requirements during dry storage. A similar germination pattern was observed in both achene types, with a germination peak in March (96% of peripheral achenes at 12, 26 and 34oC; 90% of central achenes at 26 and 34oC). The germination capacity deteriorated over time. After 19 months of dry storage, both achene morphs failed to germinate at 12oC. At a 26o and 34oC, the same group of achenes continued to germinate at a relatively high level. After six and seven months of soil storage, 90-95% of both achene types remained alive. Dimorphic achenes were characterized by similar germination percentage (89-99%) at all temperature intervals, whereas peripheral achenes exhumed in May were the fastest to germinate. After 18 months of storage in soil (successive growing season), most of the harvested achenes were dead. The studied achenes did not form a permanent seed bank.
Understanding composition, structure and spatial heterogeneity in soil seed banks is important for the management of grassland ecosystem. Although the effect of fencing and grazing on vegetation composition is widely known, information on species composition, seed density and spatial heterogeneity of soil seed banks in sandy grasslands under fencing and grazing is still lacking. We measured the species composition and seed density of soil seed banks in fenced grassland, grazed grassland and grazed shrubby grassland in Horqin Sand Land, Northern China. By applying the geostatistical methods, we assessed how fencing and grazing affected spatial heterogeneity of soil seed banks in sandy grasslands. Total seed density and species richness in soil seed banks were lower in fenced grassland than in either grazed grassland or grazed shrubby grassland. Seed density and species richness of annual species in soil seed banks were also lower in fenced grassland than in either grazed grassland or grazed shrubby grassland, while those of perennial species showed a reverse trend. The analysis of spatial autocorrelation ranges, fractal dimensions and distribution pattern maps from geostatistical methods showed that spatial heterogeneity of seed density and species richness in soil seed banks were also lower in fenced grassland than in either grazed grassland or grazed shrubby grassland. Continuous fencing increases the seed density and species richness of perennial species in soil seed banks, as well as results in a decrease in spatial heterogeneity of seed density and species richness in soil seed banks. So, continuous fencing should be considered to restore the degraded sandy grasslands in management of semiarid grassland ecosystems.
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.
We compared seed longevity of herbaceous species in three habitat types differing in stability. We hypothesized that seed longevity is the lowest for forest species (living in stable habitat), the highest for weeds, while species of xerothermic grasslands take an intermediate value. Ten species were selected from each of the three habitats with balanced representation of plant families among habitats. Seeds of the 30 species were deep buried at 65 cm depth, then replicates recovered after 1, 2, 3, 4 and 6 years, and germinated in an unheated greenhouse. Weeds expressed the highest germination rate (36.1% in average) exceeding forest (14.4%) and grassland species (10.2%) which did not differ significantly. The number of species with transient, short-term persistent and long-term persistent seed bank, respectively, was 1, 7 and 2 for grasslands; 1, 3 and 6 for forests; and 0, 1 and 9 for weeds. As expected, weeds possessed the highest seed longevity. Contrary to our assumption, low seed longevity was not the norm among forest understorey species, and seed longevity of xerothermic grassland species was not intermediate but the shortest one. Ecological background of differences between hypotheses and experimental results are discussed. First record on seed bank type is reported here for 12 species: Dianthus pontederae, Digitalis grandiflora, Ferula sadleriana, Hieracium sylvaticum, Inula ensifolia, Jurinea mollis, Lychnis coronaria, Saponaria officinalis, Scorzonera austriaca, Secale sylvestre, Stipa borysthenica, Verbascum lychnitis.
Artificial grassland establishment is one of the fastest and most effective ways to restore the productivity of degraded grasslands. Little is known about the effect of different types of artificial grassland establishment (i.e., single- and mixed-sowing grassland establishment with perennial grasses) on soil seed bank in degraded grassland ecosystems. Single-sowing population of a high yield species usually has a great standing biomass causing shading that may inhibit germination of seeds in soil seed bank. Thus, we hypothesized that there is higher species richness and seed density in the soil seed bank of single-sowing than mixed-sowing grasslands. Here, we investigated the soil seed bank in four-year old single-sowing and mixed-sowing and control (degraded) grasslands on the Qinghai-Tibetan Plateau. We found that the autumn seed bank of mixed-sowing grasslands had lower species richness and seed density than single-sowing grasslands, while the summer soil seed bank (persistent seed bank) showed little differences. There were differences in biomass among the three grasslands (single-sowing > mixed-sowing > control), but there was no differences in species richness of vegetation. In sum, our results of the autumn seed bank support our hypothesis. Greater above-ground biomass in single-sowing grasslands could generally cause low light availability preventing seeds in soil from germinating and support more seed output, which both may indirectly or directly result in the relatively higher species richness and seed density in the soil seed bank. Our results also suggest that artificial grasslands usually returning to native grasslands in terms of production and species composition after several years is likely due to stability of the persistent soil seed bank.
A new stand, formed by some fifty individuals of Ambrosia artemisiifolia L., an invasive plant of alien origin, was discovered at the Katowice railway station (southern Poland), in 2011. Two years later, the stand (increased to more than 160 individuals in the meantime) was re-visited, phytosociological survey was made, and four soil cores (5 cm deep and 80 cm² surface area, each) were taken for seed bank studies. The phytosociological sampling revealed 28 co-occurring vascular species, most of them representing hemicryptophyte and geophyte life forms. According to Ellenberg's values, the species pool indicated sunny (L7 and L8 species dominating) and semi-dry (mainly F4 species) habitat for the common ragweed population, whereas Zarzycki's soil granulometric data reflected coarse-grained soil. Albedo of the soil was lower than that of the vegetation thus sparsely vegetated sites were considered as heat accumulating microhabitats that might support establishment of the thermophilic A. artemisiifolia. During soil seed bank analysis a high number of naturally opened fruits (dehiscent achenes) were found (718.75 per m²) most probably indicating frequent germination in previous years. Greenhouse germination tests proved successful germination of 125 individuals per m², which was considered enough to maintain the A. artemisiifolia stand at the station. The results call attention to a newly discovered, established population with increasing demography of A. artemisiifolia, a highly allergenic introduced weed of Poland.
Soil waterlogging is among abiotic stresses that influence species composition and productivity in numerous plant communities. The aim of the study was to find answer to the question of how waterlogging caused by beavers’ activity induces quantitative and qualitative changes of vegetation and soil seed bank levels of variable-moist meadows. An immediate effect of the waterlogging at the level of vegetation was the decline in species richness and a decrease in the values of the biodiversity index. Water stress inhibited growth and development of plants already present and, primarily, impeded recruitment of new individuals of species characteristic of variable-moist meadows, e.g. Cirsium rivulare, Filipendula ulmaria and Lythrum salicaria, which were replaced by Carex acutiformis. Prolonged waterlogging did not induce equally substantial changes in the soil seed bank as in the vegetation. Both in the waterlogged and control patches, slightly decreased species richness and biodiversity index were recorded. After waterlogging withdrawal, the reserves of the soil seed bank were slightly higher than the initial values. The differences were not statistically significant. In the waterlogged patch, the qualitative floristic similarity between taxa identified in the soil seed bank and vegetation cover declined, which was evidenced by the value of Jaccard’s index decreasing from 0.46 to 0.36. A reverse relationship was found in control patch, where the value of the similarity index slightly increased from 0.41 to 0.48.
Seed bank composition and germination characteristics are necessary for modeling wetland vegetation composition. Yet there are few studies about the seed bank difference between plant communities in lakeshore wetlands. Seed banks are also known to play important roles in the vegetation restoration process. Environmental factors such as water level, temperature, or nutrient levels can affect vegetation composition and seed bank composition. The relationships between environmental factors and seed banks of wetlands in the field are still unknown. The Jiuzhaigou Nature Reserve is located at the eastern edge of Qinghai-Xizang Plateau. The lakeshore wetland vegetation is dominated by Phragmites australis (Cav.)Trin. ex Steud., Typha latifolia L., Carex pamirensis C. B. Clarke, Equisetum fluviatile L. The wetlands in Jiuzhaigou (118 lakes) are under strong pressure such as trampling and enhanced construction for travel. Plant restoration is necessary for protection of these areas. We investigated the soil seed bank in six lakeshore wetlands in this area using the seedling emergence method. Sediment samples (0–2 cm, 2–5 cm, 5–10 cm intervals from surface to bottom) were taken with core (diameter 5 cm) in April and from each replicate samples were spread on two plastic trays. Trays were randomly arranged in the greenhouse and watered daily. Seedlings were counted weekly after emergence, and removed as soon as they could be identified. Our study showed that seed density in all soil layers samples was negatively correlated to water depth. Water depth can explain 45% variance of species richness in surface layer in sediment. Species richness in extant vegetation can explain 45, 48, 25% variance of species richness in total 10 cm and in 2–5 cm and 5–10 cm layer sediment respectively. Dominant species cover in extant vegetation, site altitude, total nitrogen, total phosphorus and total organic carbon in soil showed no correlation with species richness in seed bank. Mean seed densities in wetlands ranged from 0 to 15945 m⁻². A total of 23 species germinated in seed bank, while 85 species were found in extant vegetation. The dominant species in seed bank and extant vegetation showed great difference. The total number of species and seedlings that germinated in different layers was not significantly different. But the second layer had the greatest seed density. The relationship between seed bank and extant vegetation differed from one species to another. We should use different restoration strategies for different plant communities.
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.
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.
Ligularia virgaurea (Maxim.) is a typical naturally-occurring native noxious weed, widely distributed in alpine grasslands of the Tibetan Plateau, China. Three field sampling plots (30 m ´ 50 m) dominated by L. virgaurea were selected to study its population colonization mode and the relationship between sexual- and clonalrecruitment in alpine meadow of the QinghaiTibetan Plateau, NW China. Field investigations were conducted on its soil seed bank, seed rain and the individuals of new recruitment (seedlings and ramets) to study its sexual and asexual recruitment. And, 46 individuals which produced the seeds were selected randomly to study their relationship between seed production and ramet production. Results showed that there were more ramets (26.23 ramets m⁻²) and less seedlings (6.70 seedlings m⁻²) and a mean value of seed rain was close to 8.04 seeds m⁻², but the soil seed bank for this species was not found in study sites. Significantly negative correlations (r = – 0.416, P <0.001) between seed number per individual and ramet number per adult individual were found for L. vrigaurea in studied alpine grasslands. Our results revealed that clonal reproduction was the main population colonization mode. In addition, there was a significantly negative relationship between seed production and ramets for this species.
Forest seed banks mostly studied in managed forests proved to be small, species poor and not reflecting aboveground species composition. Yet studies conducted in undisturbed communities indicate a different seed bank characteristic. Therefore we aimed at describing soil seed bank in an undisturbed forest in a remnant of European lowland temperate forests, the Białowieża Forest. We compared similarity between the herb layer and seed bank, similarity of seed bank between different patches, and dominance structure of species in the herb layer and in the seed bank of two related oak-hornbeam communities. We report relatively high values of Sorensen species similarity index between herb layer and seed bank of both patches. This suggests higher species similarity of the herb layer and soil seed bank in natural, unmanaged forests represented by both plots than in fragmented communities influenced by man. Although there was a set of core seed bank species present at both plots, yielding high Sorensen species similarity index values, considerable differences between plots in seed bank size and dominance structure of species were found, indicating spatial variability of studied seed bank generated by edaphic conditions. Dominance structure of species in the herb layer was not reflected in the underlying seed bank. This stresses, that natural forest regeneration cannot rely only on the seed bank, although some forest species are capable of forming soil seed banks. While forest seed banks may not reflect vegetation composition of past successional stages, they may inform on history and land use of a specific plot.
Although crucial for guiding vegetation improvement efforts, soil seed bank (SSB) and extant vegetation (EV) in dry valleys remains poorly understood. A germination method and field surveys were applied to address this problem and investigate the characteristics of SSB and corresponding EV of eight sites across the dry Minjiang River valley in Southwest China. Furthermore, the relationships between SSB and EV were compared to provide guidance for vegetation enhancement. Eight sites were classified into two groups – central and transitional sites that differ according to moisture conditions. Seed density and species richness in SSB were lower in less moist central sites compared with those in more moist transitional sites of the valley as well as the coverage of the community. Moreover, species richness and litter thickness were lower in central sites. Comparing SSB strategies of species from eight sites, transient strategy was the most frequently observed category, followed by short-term persistent and long-term persistent strategies. In terms of both SSB and EV, the most abundant life forms were hemicryptophytes, intermediate phanerophytes, and therophytes, whereas less abundant were chamaephytes and cryptophytes. Low Sorenson’s similarity indices (22–32%) and significantly negative Kendall’s correlation in species composition indicate that species composition of SSB was not closely related to corresponding EV for each of the eight sites. Low seed density, especially the lack of viable dominant shrub seeds, dominant transient SSB strategy species, and low correspondence in species composition between SSB and EV imply that the potential for vegetation enhancement in the dry valley is weak, particularly in less moist central sites. To preserve the good EV of more moist transitional sites and introduce seeds of dominant species to improve poor EV in central sites, EV is likely to be a feasible standard for improving vegetation in dry valleys.
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