Soil Seed Bank Composition Research Articles

Effects of grazing disturbances on soil seed bank diversity in two vegetation types

Soil seed bank (SSB) play an essential role in the restoration and regeneration of plant communities. Grazing is a common disturbance factor that exerts an important effect on the diversity and composition of the SSB community in forests. Here, we evaluated the structure and composition of SSB along a grazing disturbance gradient of two types of vegetation (broad-leaved forests and mixed coniferous broad-leaved forests) in southwest China. A comparison of the similarity of SSBs with the above-ground vegetation strata (tree, shrub and herb layers) was also analyzed. The experiment revealed the germination of 25 species that belonged to 14 families and 24 genera. The density of SSBs did not show significant differences along the grazing disturbance. The alpha diversity of SSBs was the highest at moderate grazing intensity in broad-leaved forests, and not significantly different along disturbance intensities in mixed coniferous broad-leaved forests. No significant changes were observed in the species composition of SSB along the grazing gradients. Nonmetric multidimensional scaling analyses revealed low similarities between SSBs and above-ground vegetation, with the lowest similarity occurring under medium grazing disturbance intensity. Overall, our research offers significant insight into the response of SSBs to grazing in different vegetation types. It serves as a guide for designing grazing management strategies tailored to natural forests.

Restoring stone and dominant grass species cover in a Mediterranean grassland: 20‐year effects on soil, vegetation, and arthropod communities

Long‐term studies are needed to monitor recovery following restoration, as it may take decades or even centuries, particularly in the case of Mediterranean dry grasslands, for communities to reach their former equilibrium before the degradation occurred. A multi‐component approach is also needed to evaluate restoration success and better understand the complex impacts of former restoration projects on present‐day ecological interactions and ecosystem functions. The objective of this study was to address the restoration of a Mediterranean grassland in southern France, 20 years after implementation. Particularly, we examine the long‐term impact on soil, vegetation, and arthropods of the reintroduction of a dominant grass species (Brachypodium retusum) and the restoration of the natural stone cover on a degraded former cultivated field. Soil analyses revealed that reestablishing stone cover only slightly acidified the soil, while B. retusum presence enhanced soil fertility. Brachypodium retusum also decreased the nutritional value of forage and increased plant biomass and litter. Plant composition shifted with treatments: B. retusum and stone cover favored xeromesophilous species, while B. retusum alone encouraged less palatable species. The soil seed bank composition and abundance were positively influenced by stone cover but negatively impacted by B. retusum reintroduction. Negative outcomes on some arthropods and mesofauna were measured in treatments with both B. retusum and stones, except for Acari, which were positively impacted by the presence of stones. The findings emphasize that B. retusum is an ecological engineer with complex effects on the different ecosystem components.

The importance of soil seed banks for biodiversity restoration in degraded grasslands

To effectively restore species and habitat diversity in poorly managed degraded grasslands, it is important to understand the relationship between the soil seed bank and aboveground vegetation. Our study aimed to describe changes in soil seed bank composition compared to aboveground vegetation under two ploughing regimes (annual and single ploughing) of narrow strips on the edges of artificially grassed old fields in Podyjí National Park, the Czech Republic. We used the seed germination method, multivariate analyses and Kruskal–Wallis tests to compare differences in the proportion of species and individual numbers in the soil seed bank based on the origin of species (native species, archaeophytes, neophytes) and their habitat preferences (segetal, ruderal, grassland, endangered species) in two types of grasslands with varying soil moisture content. The highest numbers of individuals were present in annually ploughed dry grasslands whereas single ploughing in mesic grasslands resulted in greater species diversity. Ploughing increased the numbers of seedlings of all groups and promoted archaeophytes, grassland specialists, native species and ruderals in dry grasslands whereas mesic grasslands hosted segetal specialists and neophytes. Threatened plants and invasive species rarely emerged from the soil seed bank. The study also revealed the highest similarity between the soil seed bank and aboveground vegetation in annually ploughed plots. It gradually decreased during vegetation succession in the single ploughed variants. Whereas annual ploughing supported segetal specialists, single ploughing promoted grassland species in dry habitats. Neither type of ploughing can be recommended in mesic grasslands because of the risk of inducing the spread of expansive ruderals or invasive neophytes.

Study of the Soil Seed Bank Composition in Arjo-Diga Humid Afromontane Forest under Different Land Use Types and Its Implications for the Restoration of Degraded Lands in Western Ethiopia

The soil seed bank present in forests serves as a crucial indicator of soil resilience following disturbances. The objective of this study was to investigate the composition, density, and vertical distribution of the soil seed bank in the Diga District of Western Ethiopia across four land use types: forestland, grassland, bare land, and shrubland. Soil samples were collected from plots measuring 225 square centimeters with a depth of 9 cm. A total of 108 soil samples were collected, representing the four land use types. Each plot was sampled at three different soil layers: 0–3 cm, 3–6 cm, and 6–9 cm depths. From the soil seed bank, 51 plant species were identified, with 46 (90.2%) being herbs, 3 (5.88%) trees, and 2 (3.92%) shrubs. The Asteraceae (13.30%), Poaceae (11.53%), and Fabaceae (9.61%) families exhibited the highest species composition, accounting for 38.44% of the total. Species richness varied significantly across all land use types and soil layers (p<0.05), with shrubland having the highest species richness and bare land having the lowest count. The total seed bank density in the soil across all plots was 92153 seeds/m2, with the highest density observed in the top 3 cm of the soil layer. The first and second soil layers exhibited a high Jaccard similarity coefficient of 0.76. Forestland and shrubland displayed the highest Jaccard coefficient of similarity (0.72), while the lowest was observed between bare land and shrubland (0.43). There was greater species similarity between the first and second soil layers (0.76) and lower similarity between the middle and bottom layers (0.32). The study found limited similarity between aboveground vegetation and the soil seed bank due to the low regeneration of woody species. Forestland and shrubland exhibited a high Jaccard similarity coefficient to aboveground vegetation, while grassland had the lowest similarity coefficient. Based on the findings, it can be concluded that the shrubland land use types had high soil seed bank composition and density. Therefore, the conservation of shrubs in the Arjo-Diga Forest should be considered for the restoration of degraded areas, taking into account the soil seed bank in the shrubland ecosystem.

Contribution of soil seed banks to vegetation resilience in coastal freshwater wetlands of subtropical Australia

AbstractQuestionsWhat role do soil seed banks play in the resilience of coastal freshwater wetland vegetation communities? How might soil seed bank composition and similarity to standing vegetation drive changes in vegetation expression, particularly given projected changes in climate?LocationSixty wooded coastal freshwater wetlands in southeast Queensland, Australia.MethodsWe surveyed standing vegetation and investigated soil seed bank composition through an 8‐month‐long emergence experiment.ResultsSoil seed bank assemblages were dominated by forb and sedge species (23% exotic), but composition varied throughout the study region. Spatial (north–south) and land‐use (urban–rural) gradients explained some variation in soil seed bank composition. Soil moisture and groundwater dependence also influenced species distributions, particularly for freshwater wetland species. The similarity of soil seed banks to standing vegetation was low. Species present in both extant and soil seed bank assemblages were commonly native wetland taxa, including one salt marsh species (Juncus kraussii).ConclusionsProjected climatic changes will likely drive changes in coastal freshwater wetland vegetation communities through increases in the frequency and intensity of disturbances (e.g., storm surge). Our results suggest that regeneration from soil seed banks could promote four potential scenarios: (1) expansion of weed communities, (2) expansion of salt marsh communities, (3) maintenance and expansion of wetland/terrestrial species, and (4) transformation to an unvegetated open water zone because of reduced regeneration success under changing conditions. These diverse vegetation futures highlight the vulnerability of wooded coastal freshwater wetlands and the need for research and management interventions to maintain their biodiversity and ecosystem services.

Reduced plant species diversity and soil carbon and nitrogen contents driven by vegetation patchiness in alpine meadows

AbstractQuestionPatchiness of herbaceous species is a common feature of degraded alpine grasslands on the Qinghai–Tibet Plateau; however, the impact of this phenomenon on vegetation, soil seed bank (SSB), and soil carbon (C) and nitrogen (N) is largely unknown. We asked how different herbaceous patches affect above‐ground vegetation, the SSB and soil organic C (SOC) and total N (TN) contents in alpine meadows.LocationAn alpine meadow on the Qinghai–Tibetan Plateau, China.MethodsWe used field and greenhouse experiments to evaluate above‐ground vegetation parameters, the SSB composition, and SOC and TN contents of four commonly distributed herbaceous patches (Leymus secalinus, Kobresia humilis, Leontopodium nanum and Pedicularis kansuensis) and non‐patch vegetation (control).ResultsThere were significant differences in the species composition of above‐ground vegetation, with the plant species richness, Shannon–Wiener index, Simpson index, and Pielou evenness index reduced in the four patches compared to the control. In addition, patches had increased above‐ground biomass (AGB) and a lower below‐ground biomass to above‐ground biomass ratio (BGB:AGB); while the species diversity indices did not change considerably among the patches. The species composition of the SSB in the four patches differed from that in the control and the seed density increased markedly, but the species richness and diversity of the SSB remained unaltered. Moreover, the contents of SOC, total C, TN, microbial biomass C, and microbial biomass N in the four patches were markedly lower than in the control.ConclusionsThese findings suggest that patchiness of herbaceous species can alter the flora composition of alpine meadows and reduce plant species diversity, as well as the SOC and TN contents, which will adversely impact grassland biodiversity conservation and soil C sequestration, and then may intensify the degradation of alpine meadows on the Qinghai–Tibet Plateau.

Potential contributions of the soil seed bank and seed rain for accelerating the restoration of riparian catchments in Australia

The quality and quantity of soil seed bank composition can play a key role in secondary succession restoration efforts such as those involved in this study, which concerned the restoration of damaged native sites in riparian environments in Victoria, Australia. The objective of this study of the restoration work was to determine the role played by naturally existing soil seed bank in the success of natural restoration in these restored and unmanaged riparian areas. In this regard, we sampled the soil seed bank, seed rain, seedlings in the field and vegetation cover from three sub catchments defined by restoration attempts which had been conducted (i) < 3 years, (ii) 4–8 years, and (iii) > 9 years previous to sampling. In addition, (iv) in order to provide comparative data, adjacent sites (iv) chosen for future restoration and (v) with remnant vegetation, were also sampled. From samples, a total of 8858 seedlings were recorded from the seed bank and the vegetation survey showed 170 species, with exotic species being more numerous than native. The seed rain (a total of 1422 seeds) was dominated by exotic species at all sites. When comparing the vegetation distribution and the seed rain composition, it was clear that whilst the seed bank was more promising as a comparative recruitment source of native species, there were still too many sites dominated by exotic species to rely on this as a long-term restoration strategy. However, this study indicated that there were significant variations in restoration potential among the sites, suggesting that some careful prior site selection for investment of restoration efforts is an important issue. As a consequence, we have recommended that a detailed understanding of the soil seed bank and seed rain species composition prior to the restoration is essential, since a positive seed bank composition with a significant relative density of native species seeds, will provide an indication of native species’ resilience and their potential for recovery. We therefore believe that the findings of this study will provide valuable information to natural resource management agencies regarding the strategy for prioritisation of restoration sites, which will be more beneficial than randomly selecting sites for habitat restoration. In addition, with successful sector restoration, it is expected that the increasing usefulness of the seed bank will allow further restoration of adjacent areas with time.

Quantifying shrub encroachment through soil seed bank analysis in the Ethiopian highlands.

This study aimed to understand the impact of shrub encroachment on native species in the Guassa Community Conservation Area in Ethiopia. We assessed the soil seed bank composition and density across different elevations and aspects, and management systems within the area. The vegetation was stratified and eight blocks were selected across a range of elevation (<3350 m and >3350 m) and aspect (northeast, northwest, southeast, southwest). Within each block we established twenty 5m x 5m plots for a total of 160. We then collected soil samples from five subplots (1 m x 1 m) at three depths (0-3 cm, 3-6 cm and 6-9 cm) for a total of 480 samples, which were established in pots in greenhouse. We calculated species abundance by totaling the number of seedlings that emerged from each sample. To determine the variability in the abundance of Festuca macrophylla and Helichrysum splendidum in the soil seed bank along altitudinal gradient, we used two-way ANOVA using SAS statistical software version 9.0.1. Shannon diversity index was used to determine species diversity in the soil seedbank. After counting all the seeds, we identified 74 plant species represented in the soil seedbank which belong to 55 genera and 23 families. Eleven species are endemic to Ethiopia. At the lower elevation range, the effects of aspect (P <0.0088) and soil depth (P <0.005) are not significant to determine the abundance of seeds of H. splendidum and F. macrophylla. But when the factors are segregated, both aspect and soil depth play a significant role (p<0.0001) regarding the abundance of the seeds of the competing species at lower elevation. At higher elevation, only the effect of soil depth is significant (P<0.0001) for determining the abundance of H. splendidum. Soil depth and aspect have no significant effects on soil seed bank abundance at this elevation.

Soil Seed Bank Composition and Spatial Distribution in a Cheatgrass (Bromus tectorum L.)–Dominated Rangeland in Colorado, USA

Soil Seed Bank Composition and Spatial Distribution in a Cheatgrass (Bromus tectorum L.)–Dominated Rangeland in Colorado, USA

Seed banks and seed survival of submersion for an emerging plant invader in the Colorado River system, USA

AbstractSoil seed banks along shorelines and the ability of seeds to survive submersion in water are among potential factors that can influence seed supply, a frequent driver of riparian plant invasions. We investigated germinable soil seed banks and the ability of seeds to germinate after different durations of submersion in water for non‐native ravennagrass (Saccharum ravennae), an emerging but poorly understood invader of riparian habitats in the American Southwest, including along the Lake Powell section of the Colorado River where we performed the study. We assessed soil seed bank composition in 27 ravennagrass‐invaded plots using the emergence technique and evaluated effects on ravennagrass germination of submersion in river water for up to 15 months in a laboratory experiment. Ravennagrass was sparse in soil seed banks, detected in samples from only one of the 27 plots. Instead, soil seed banks were dominated by the non‐native annual cheatgrass (Bromus tectorum) and a mixture of native early colonizers (e.g., Pseudognaphalium stramineum) and shrubs (e.g., Baccharis emoryi). Although ravennagrass seed germination was low (&lt;9%) in the submersion experiment, some seeds retained germinability after 15 months of continuous submersion in water. Results suggest that while ravennagrass may have limited on‐site, readily germinable soil seed banks, potential implications of its protracted seed viability in water for dispersal along waterways warrants further attention.

Is the soil seed bank a reliable source for passive restoration of intensive grazed habitats in river riparian areas of western Iran?

Soil seed banks serve as reservoirs of seeds for subsequent regeneration of plants particularly in areas prone to disturbance, such as intensive grazed areas along rivers. The potential of soil seed bank (SSB) for vegetation restoration was assessed in overgrazed riparian areas in Gamasyab river, Iran. Therefore, SSB composition, density and diversity and, its relationship with aboveground vegetation (AGV) were investigated along the river. Fifteen transects were set perpendicular to the river and along each transect, 6 plots (1 m × 1 m) were established, in total 90 plots. In each plot, soil was collected for SSB experiments and AGV was sampled during the growing season. The similarity between SSB and AGV was estimated by the Jaccard similarity index and non-metric dimensional scaling (NMDS). Spatial beta diversity was calculated by the mean Bray-Curtis index for the SSB and vegetation compositions, separately. A total of 136, 108 and 134 species were identified in the upper (0–5 cm) and lower (5–10 cm) soil layers and, AGV, respectively. Annual and perennial grasses were dominant in SSB composition at 0–5 cm depth while the frequency of perennial grasses was highest in SSB at deeper depth and vegetation composition. The beta diversity of AGV was significantly higher than for SSB. Similarity between SSB and vegetation was low (7.92%–22.40%), nevertheless, most species in AGV were found frequently in the SSB. So, we argued that restoration of degraded vegetation in our riparian could rely on SSB. It is expected that after grazing exclosure, vegetation would restore mostly with perennial grasses through SSB and vegetative growth.

Buffering effects of the soil seed bank on annual plant community composition after wetland drying

AbstractSubalpine peat wetlands are extremely sensitive to global environmental changes and anthropogenic disturbances. Unlike most other biological groups, plant species can possess dormant life‐history stages such as the soil seed bank (SSB), which may help plant communities to resist or at least postpone the detrimental impact of disturbance. This study investigates the potential for SSB to achieve this along a soil moisture gradient. Species richness and density of SSB were significantly lower by 31.9% and 47.2% in wetland, and 35.1% and 68.1% in swamp meadow in comparison with steppe meadow, respectively. Soil moisture content did not directly affect the density and species richness of SSB, whilst had indirect effects on density and species richness via affecting vegetation and soil pH. SSB composition was less responsive to soil moisture changes than plant community composition. Furthermore, compositional trends in the annual plant SSB were weaker than in the aboveground vegetation along the soil moisture gradient. The similarity between SSB and vegetation significantly declined with increasing soil moisture content. High SSB diversity and compositional similarity between the vegetation and SSB may provide a potentially important functional buffer against the impact of ongoing moisture changes on plant communities in wetlands. Dormant life‐history stages can therefore be important sources of diversity in changing environments. Furthermore, although SSB has low regeneration potential for the aboveground vegetation communities in subalpine peat wetlands, the SSB would still not be a neglected factor for the restoration of propagule diversity after disturbance in wetlands if hydrology is restored.

Altitude patterns of seed C, N, and P concentrations and their stoichiometry in an alpine meadow on the eastern Tibetan Plateau

Understanding the altitudinal patterns of plant stoichiometry in seeds is critical for characterizing important germination and dormancy strategies, soil seed bank composition, seed predation probability, efficiency of seed dispersal and seedling performance, and to predict how biodiversity might be influenced by climate change. However, our understanding of the altitudinal patterns of seed stoichiometry is extremely limited. In this study, we measured the concentrations of carbon (C), nitrogen (N) and phosphorus (P) in the seeds of 253 herbaceous species along an altitudinal transect (2,000–4,200 m) on the eastern Tibetan Plateau, China, and further to characterize seed C:N:P stoichiometry. The geometric means of C, N, and P concentrations were 569.75 mg/g, 34.76 mg/g, and 5.03 mg/g, respectively. The C:N, C:P, and N:P ratios were 16.39, 113.31, and 6.91, respectively. The seed C, N, and P concentrations and C:N:P ratios varied widely among major plant groups and showed significant altitudinal trends. In general, C, N, and P concentrations increased, whereas seed C:N:P ratios decreased with elevation. These results inform our understanding of the altitudinal patterns of seed stoichiometry and how to model ecosystem nutrient cycling.

Composition and Spatial Variation of Germinable Seed Bank in Burned Nothofagus pumilio Forests in Patagonia Argentina

The availability of soil-stored seed determines initial plant functional types in post-fire landscapes. We evaluated the post-fire regeneration of Nothofagus pumilio forests, in Patagonia, Argentina, analyzing the soil seed bank (SSB) and the above-ground vegetation (AV). At three sites: La Colisión, Río Turbio and Monte Zeballos, burned in 2008, 1980 and 1941, respectively, we sampled the SSB and AV in two transects from the edge of the remaining forest, up to 90 m within the burned area, and recorded the emergence (198 soil samples) and presence of vascular species. To determine the effect of the distance to the remnant forest on the germinable seed bank, we performed simple linear regression analysis through the use of linear mixed-effect models, and we analyzed the similarity between the composition of SSB and AV with PERMANOVA. The emergence of plant growth forms had different patterns in relation to the distance from the forest in the three sites, which might be associated with the time of fire occurrence, and specific characteristics of each site. The emergence of N. pumilio was registered at more than one distance at the recent burning site. Herbs constituted the main source of cover with 69% of the composition, and native/endemic species represented 71%. This study contributes to the understanding of the relationship between the seed bank and standing vegetation and a better understanding of the resilience of post-fire N. pumilio forests. Our findings suggest that from 15–20 m from the edge, the SSB would be insufficient to ensure the spontaneous recovery of the forest, making active restoration necessary in order to tend to a recovery of the structure and functionality of the original community.

Fire effects on soil seed banks under different woody plant species in Mazandaran province, Iran

Soil seed banks play a major role in the post-fire regeneration of semi-arid mountain grasslands. Plant species present before fire can determine the soil seed bank (SSB) characteristics in fire-prone ecosystems. However, it remains unclear how the density and species composition of the SSB under the canopy cover of specific shrub species may be affected by fire. Therefore, we designed a study to test the effects of prescribed burning on the viable SSBs under the canopies of two shrub species: Berberis integerrima (with open canopies) and Onobrychis cornuta (with dense canopies). We selected 20 study sites that included separate patches of the two shrub species and nearby herbaceous patches as control. Soil sampling was carried out pre- and post-burning of shrub canopies and the control patch. Soil samples were collected at two depths: 0–5 cm and 5–10 cm, and transported to the greenhouse for germination experiments. The results showed that canopy fire of shrubs decreased SSB density and species richness. However, the effects of shrub burning on SSB were species-specific and these reductions were more pronounced for canopy burning of O. cornuta than for B. integerrima. Total SSB densities decreased by 61% for B. integerrima and 71% for O. cornuta after canopy fire at soil depth of 0–5 cm. At soil depth of 5–10 cm, total SSB density decreased by 45% under O. cornuta after canopy fire, while canopy fire of B. integerrima did not affect SSB density. Herbaceous patch burning had no statistically significant effects on SSB density at soil depths of 0–5 cm and 5–10 cm. The comparison of quantitative and qualitative similarity indices between pre- and post-fire species composition of shrub canopy showed that the statistically significant effect of B. integerrima burning on SSB composition was less pronounced compared with O. cornuta. This study indicated that seeds stored within the soil under certain shrub species are at a high risk of mortality during fire. Thus, successful post-fire recovery does not rely on the seed bank reservoir under these shrubs.

Comparison of Aboveground Vegetation and Soil Seed Bank Composition among Three Typical Vegetation Types in the Karst Regions of Southwest China

Rural agricultural activity generates cropland, secondary vegetation and straggling primary forest and can modify the soil seed bank (SSB), potentially impacting the restoration of preferred species. The interaction between vegetation and seed banks during the recovery process is dependent on management practices and recovery pathways. This study was carried out in Guilin of southwest China to assess the variation in plant diversity and species composition of both aboveground and soil seed banks across three typical vegetation types with different human interventions: orchard, bamboo shrub and primary forest. The results show that there were significant differences in the species composition and diversity of aboveground vegetation and SSB, as well as in soil properties among three typical vegetation types. The primary forest had the highest aboveground species diversity, while the orchard had the highest species diversity and seed density of SSB. In addition, principal component analysis (PCA) and canonical correspondence analyses (CCAs) showed that the species composition and plant life forms of the three typical vegetation types were significantly influenced by soil properties. Based on these findings, the characteristics of aboveground vegetation and the soil seed bank and their correlations with soil properties are expected to drastically change with human intervention. These results imply that unsustainable land use has greatly impacted soil properties, and consequently, the aboveground vegetation and SSB. Nevertheless, vegetation will recover quickly after farming is abandoned. The successful restoration of fragmented ecosystems requires the addition of seeds and seedlings of target species, especially perennial woody plants from the relevant natural ecosystems, to accelerate succession from bamboo shrub to forest.

Soil seed bank composition and aboveground vegetation in dry Afromontane forest patches of Northwestern Ethiopia

The species composition in the aboveground vegetation and soil seed bank (SSB) were described for the dry Afromontane forest patches of Northwestern Ethiopia. Plots (30 × 30 m) were established to collect the vegetation and environmental data. Soil samples were collected for the soil bank study from the small plots measuring 10 cm × 10 cm from four soil layers. Shannon Weiner index and evenness were used to assess the species diversity and richness of the forest. Density, DBH, basal area, frequency, and importance value indices (IVI) of woody species were computed to characterize the vegetation structure of the forest. Results indicate the presence of 176 plant species belonging to 80 families. The Shannon diversity index and evenness values of the study area were 2.79 and 0.95, respectively were medium, compared to other dry Afromontane forests of Ethiopia. The total basal area and density of woody species were 51.42 m2 ha−1 and 2679.33 individual ha−1, respectively. The most dominant species as and indicated by their important value index (lVI) was Prunus africana (17.97). A total of 2133 seedlings belonging to 44 species and 27 families were identified from the soil seed bank, with a viable seed density of 4636.95seeds/m2. The species composition of the seed bank was dominated by 29 herb species (65.9%) compared to 2 tree species, which accounted for only 4.54% of the total number of species. The highest number of species density was recorded in the litter and the upper 3 cm layer of the soil and gradually decreased with increasing depth. The Similarity between soil seed bank species composition and aboveground vegetation was low and conclude that the regeneration potential of the forest from seed bank is limited. Redundancy analysis (RDA) showed that emerged seedlings from the soil seed bank were significantly influenced by elevation and soil cation exchange capacity. The natural regeneration process of soil seed bank should be assisted through transplanting indigenous tree species in to the forests to accelerate the restoration of the vegetation and conservation and sustainable utilization of the reaming of forest patches is a necessity.

Farming Intensity Affects Soil Seedbank Composition and Spontaneous Vegetation of Arable Weeds

Former studies carried out in the 2000s in the Lahn-Dill region located in the middle-east of the German state Hesse stated a depletion of arable weeds on the field scale and more diverse weed flora on the landscape scale. Current study, having started in 2018, aims to contribute to a better understanding of the interactions between arable weed species diversity, farming intensity, grown crops and landscape area. Moreover, the potential of organic farming methods for conservation and promotion the arable weed diversity is aimed to be assessed with the study. In total, 42 fields in two landscape regions were sampled—six seedbank samples were collected from each field; additionally, data on spontaneous arable weed flora were recorded each spring from 2019 to 2021; emerged aboveground weeds were identified in the fields and their coverage was documented. Four factors were considered in the field trial: Farming practice, landscape area, soil depth and the current crop. Effects of these factors on arable weed species diversity were calculated with a Generalized Linear Model (GLM), resulting in significant effects of the management system, the area and the current crop. Among the four organic farming systems that were sampled, the time period of organic growing had a significant effect on weed seed numbers in the soil with an increase in seed numbers. Average seedbank species numbers were around twice as high in organic farming systems (18 species) compared to conventional managed fields (nine species). Evidence of an ongoing species decline in the region on the landscape scale could be detected by comparison with a former study. Especially rare and endangered weed species are a concern due to seedbank and current vegetation depletion tendencies.

Influence of Simulated Nitrogen Deposition on the Soil Seed Bank of a Subtropical Evergreen Broadleaved Forest

Increased nitrogen (N) deposition may have profound effects on forest ecosystems. However, information on the impacts of elevated N deposition on belowground soil seed bank in forests is lacking. In a field experiment, we added N at 50 and 25 kg N ha−1 year−1 to the canopy (CAN50 and CAN25) and to the understory (UAN50 and UAN25), to determine the effects of N deposition on soil seed bank structure and composition in a subtropical evergreen broadleaved forest. A total of 1545 seedlings belonging to 37 species emerged from the 10 cm-depth soil samples. After 6 years of N addition, soil seed bank density significantly increased at the depth of 0–10 cm under CAN50 treatment relative to the control. N addition did not significantly affect species richness, the Simpson index, Shannon–Wiener index, or Pielou index of the soil seed banks. Seed bank density and species richness were positively correlated with soil organic matter content. For the whole 0–10 cm soil layer, the percentage of total seed abundance and total species richness represented by tree species among the N-addition treatments was ≤9.3% and ≤16.1%, respectively. Soil seed bank composition was similar among UAN25, UAN50, and the control, but canopy N addition and especially CAN50 altered the species composition of the seed bank. Overall, our results indicate that artificial canopy N deposition at 50 kg N ha−1 year−1 but not understory N addition tends to promote seed storage and to change species composition in the soil seed bank. Because of the dominance of shrubs and herbs in the soil seed bank, the potential to regenerate tree species from the soil seed bank is limited in the subtropical evergreen broadleaved forest.

Species richness, diversity, density and spatial distribution of soil seed banks in the riparian woodland along the Thamalakane River of the Okavango Delta, northern Botswana

Soil seed banks serve as reservoirs of seeds for subsequent regeneration of plants. Soil seed banks were investigated along the Thamalakane Riparian Woodlands (hereafter referred to as TRWs) of the Okavango Delta, northern Botswana, from January-July 2015 and January-July 2016. The study aimed at examining species richness and diversity, determining densities, assessing the spatial distribution of seeds in the soil and comparing the similarity in species composition between the standing vegetation and soil seed bank flora. The vegetation was sampled in 71 plots (20 × 50 m) and soil samples were collected from 568 subplots. Agglomerative hierarchical cluster analysis was used to determine soil seed bank communities. Indicator species analysis was used to calculate indicator values for species in each community of germinated seeds and across different soil layers. Multi-response permutation procedures (MRPP) were used to compare similarity in soil seed bank composition. Bray-Curtis ordination was used to infer spatial relationships of soil layers in terms of soil seed bank composition. A total of 109 plant species were identified in the litter and top 9 cm soil layers with a mean density of 2101 seeds m−2. Herbs, grasses, sedges and woody plants were represented by 68, 19, 9 and 13 species, respectively, in 30 families and 87 genera. The overall total diversity and evenness of the soil seed bank in the TRWs was 3.25 and 0.69, respectively. Four plant communities were identified from the soil seed bank, namely Setaria verticilata-Amaranthus hybridus, Acanthospermum hispidum-Setaria sagittifolia, Digitaria eriantha-Eclipta prostrata and Cyperus longus-Fimbristylis dichotoma. Bray-Curtis ordination showed that there was overlap between these communities in terms of seed bank composition. However, MRPP analysis showed that there was significant (P < 0.05) separation between germinated soil seed bank communities. The overall horizontal distribution of seeds varied among sampling quadrats while the vertical distribution of seeds exhibited the highest densities occurring in the upper 3 cm of the soil and gradually decreasing densities with increasing depth. Relatively high densities also occurred in the litter layer. There were large differences in depth distribution between species, suggesting differences in seed longevity. The similarity in species composition between the soil seed flora and standing vegetation was low (27%). The results demonstrated that many species in TRWs store quantities of seeds in the soil. The fact that most of the woody species do not accumulate more seeds in the soil suggests that their regeneration from seeds would be unlikely if mature individuals disappeared (die or are harvested). Because of its diverse seed banks, the herbaceous flora would have a better chance of re-establishing in the event of anthropogenic or natural disturbances. Therefore, the future of the TRW woody flora seems to depend on the successful conservation of the standing vegetation.