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Seasonal Variation in the Seed Banks of Herbaceous Species in Ten Contrasting Habitats
Journal of Ecology
Abstract
(1) Measurements have been made of seasonal variation in the density and composition of the reservoir of germinable seeds present in surface (0-3 cm) soil samples collected at 6-weekly intervals from ten ecologically-contrasted sites in the Sheffield region. (2) The procedure was not designed to provide a complete assessment of the seed flora, and the methods were found to be ineffective in recovering germinable seeds of those species (e.g. Endymion non-scriptus, Viola riviniana, several Umbelliferae) in which there is only a brief interval between fulfilment of a chilling requirement and the onset of germination. (3) The techniques adopted were particularly suitable for the detection of persistent seed banks (i.e. those in which some of the component seeds are at least 1 year old), and also allowed recognition of species in which there is a transient accumulation of detached germinable seeds during the summer. (4) Comparison of the results obtained for populations of the same species in different types of habitat suggests that seasonal variation in seed number is a function of the species rather than of the environment. (5) It is concluded that the major evolutionary force determining the nature of the seed bank is the selective advantage derived from mechanisms of seed dormancy and germination which allow seedlings to evade the potentially-dominating effects of established plants. (6) From the data collected in this study, four types of seed bank (Types I-IV) have been recognized, and an attempt has been made to assess their ecological significance. (7) The transient seed banks (Types I and II) are adapted to exploit the gaps created by seasonally-predictable damage and mortality in the vegetation, whilst the persistent seed bank (Type IV) confers the potential for regeneration in circumstances where disturbance of the established vegetation is temporally and/or spatially unpredictable. A second type of persistent seed bank (Type III) has characteristics intermediate between those of Types I and IV, and contains some seeds which germinate soon after release and others which are more persistent in the soil. (8) A feature of the results was the lack of a general correspondence between the species-composition of the seed flora and that of the associated vegetation. At certain sites, substantial persistent seed banks were detected for species which were either extremely scarce or did not occur at all in the established vegetation. (9) Both transient and persistent types of seed banks were represented at each of the ten sites; this is consistent with the hypothesis that complementary mechanisms of regeneration are involved in the maintenance of floristic diversity.
... The soil seed bank comprises all viable seeds that appear in the soil and its surface litter and serves as a reproductive source for vegetation survival, dispersal, and establishment (Thompson and Grime, 1979). It plays a significant role in vegetation restoration, succession, and the conservation of species diversity within plant populations (Kassahun et al., 2009;Dreber et al., 2011;Yang and Li, 2013;M. ...
... In mature and stable habitats, perennial plants tend to have lower seed-set but higher capacity for vegetative reproduction, resulting in a limited contribution to seed banks (Thompson et al., 1998;Ma et al., 2012). In addition, many studies have found that plant species in disturbed areas are more inclined to produce a greater number of seeds through sexual reproduction than those in the less disturbed areas (Thompson and Grime, 1979;Chu et al., 2019). In this study, it is likely that the plants in the LRW were pioneer species at the beginning of succession in this new habitat, which tend to reproduce by high seed-set, and may have caused the highest seed bank density (Crain et al., 2004;Fu et al., 2011). ...
... Many studies have found that plant species in disturbed areas tend to allocate resources for sexual reproduction to adapt to changing environments (Thompson and Grime, 1979;Chu et al., 2019). Remarkably, there were no significant differences in above-ground vegetation density among the three wetlands, whereas the seed bank density exhibited a significant improvement after reclamation. ...
... Soil seed bank (SSB) refers to the total number of viable seeds remaining on the soil surface and in the soil below (Thompson and Grime, 1979). These seeds serve as critical capital for vegetation regeneration and recovery after disturbance variables (e.g., fire, grazing, aridity) (Baskin and Baskin, 1998;DeMalach et al., 2021DeMalach et al., , 2023Eskelinen et al., 2023;He et al., 2021). ...
... For example, Ma et al. (2017) found that above-ground vegetation indirectly influences SSB composition by modifying moisture, soil and light conditions within their environments in the grassland of the Qinghai-Tibet Plateau. Moreover, the similarity between above-ground vegetation and SSBs can also be affected by disturbance factors (Bossuyt and Honnay, 2008;Chang et al., 2001;Shi et al., 2022;Thompson and Grime, 1979). ...
... This is based on how long viable, ungerminated seeds remain in the soil [1]. Transient species exist in the seed bank for less than 1 year, while persistent species remain for more than 1 year [1][2][3]. Understanding the factors that affect species' probability of forming a persistent soil seed bank can contribute to better predictions of changes in populations and communities under global changes such as biotic invasions, warming or habitat fragmentation [4][5][6][7][8]. The prediction of seed bank persistence has been an issue that ecologists have explored for many years, with particular emphasis on the ...
... To unify the seed persistence classifications of the original studies, we grouped species into two classes [1,2]: transient vs. persistent. Transient seeds existed in the soil for less than 1 or 2 years, while persistent seeds existed in the soil for at least 1 or 2 years (details in electronic supplementary material, table S1). ...
There is some evidence that seed traits can affect the long-term persistence of seeds in the soil. However, findings on this topic have differed between systems. Here, we brought together a worldwide database of seed persistence data for 1474 species to test the generality of seed mass–shape–persistence relationships. We found a significant trend for low seed persistence to be associated with larger and less spherical seeds. However, the relationship varied across different clades, growth forms and species ecological preferences. Specifically, relationships of seed mass–shape–persistence were more pronounced in Poales than in other order clades. Herbaceous species that tend to be found in sites with low soil sand content and precipitation have stronger relationships between seed shape and persistence than in sites with higher soil sand content and precipitation. For the woody plants, the relationship between persistence and seed morphology was stronger in sites with high soil sand content and low precipitation than in sites with low soil sand content and higher precipitation. Improving the ability to predict the soil seed bank formation process, including burial and persistence, could benefit the utilization of seed morphology–persistence relationships in management strategies for vegetation restoration and controlling species invasion across diverse vegetation types and environments.
... Seasonal changes in rainfall and temperature may affect the formation and composition of the soil seed bank (Thompson and Grime 1979;Garwood 1989 Soil seed banks are an important mechanism for the resilience and persistence of some species in the above ground community (Baskin and Baskin 2014;Yang et al. 2021 ...
... Comparing the soil seed bank with the above ground community, the families with the highest species richness were Vochysiaceae, Bignoniaceae (Francisco 2020); Rubiaceae, Myrtaceae, Lauraceae (Francisco 2020; Santos 2020), and Fabaceae (Weiser 2007; Francisco 2020; Santos 2020). From these, we found only Fabaceae and Rubiaceae; however, the species presented in the soil seed bank not always are the same in the above ground vegetation(Thompson and Grime 1979;Townsend et al. 2010). ...
Understanding the composition of the soil seed bank, as well as the influence of seasonality and light on seed germination, is crucial for comprehending how changes in these conditions impact the recruitment of new individuals in the aboveground community, the dynamics of natural regeneration, and responses to disturbances. In this study, we investigated the effects of seasonality and light on the abundance, species richness, and diversity of the soil seed bank. The study was conducted in the woodland savanna of Glebe II, located within the Aimorés Wildlife Refuge, which is part of the Mosaic of Conservation Units of São Paulo State Savanna, in southeastern Brazil. We analyzed the soil seed bank using the seedling emergence method in both dry and rainy seasons. Soil was collected from 25 permanent plots, divided equally. One part was placed for germination in a nursery with a polyethylene screen cover, providing 14% shading (light treatment), while the other part was placed in a nursery with a polyethylene screen cover, providing 70% shading (shady treatment). Abundance, species richness, and diversity were evaluated for each season and treatment. Our results revealed greater abundance and species richness in the soil seed bank collected during the rainy season and maintained under shady treatment. In contrast, we observed greater diversity in the soil seed bank collected during the dry season and maintained under light treatment. These findings demonstrate that seasonality and light conditions have distinct effects on different attributes of the soil seed bank in the woodland savanna.
... Rumex obtusifolius is able to flower several times annually, and large plants can produce up to 60,000 seeds in a single year [4]. Zaller [1] noted that many seeds just fall to the ground near the parent plant, and following Cavers and Harper [4] seed survival in R. obtusifolius can be up to 40 years, which suggests that the species can build a persistent seed bank (sensu Thompson et al. [5]) given sufficient opportunity for seed set. Seeds of R. obtusifolius have high germination rates when exposed to light and fluctuating temperatures [6][7][8]. ...
... However, fresh ripe seeds of R. obtusifolius have innate dormancy [43] and a fraction of these seeds can become covered by litter and/or be buried in the topsoil by precipitation [25] or the activity of mice, earthworms or livestock [44, page 137]. Because a soil cover of only 2-3 cm strongly reduces germination in R. obtusifolius [9,10], over time these seeds accumulate in the soil and can form a persistent seed bank [5]. Given the low proportion of seeds that remain viable at the soil surface or the topmost soil layer [45], our results imply that in the grasslands included in our study R. obtusifolius must have repeatedly formed seeds in the past, including the preceding five years prior to investigation. ...
Rumex obtusifolius is a problematic weed in temperate grasslands worldwide as it decreases yield and nutritional value of forage. Because the species can recruit from the seed bank, we determined the effect of management and soil properties on the soil seed bank of R. obtusifolius in intensively managed, permanent grasslands in Switzerland (CH), Slovenia (SI), and United Kingdom (UK). Following a paired case-control design, soil cores were taken from the topsoil of grassland with a high density of R. obtusifolius plants (cases) and from nearby parcels with very low R. obtusifolius density (controls). Data on grassland management, soil nutrients, pH, soil texture, and density of R. obtusifolius plants were also collected. Seeds in the soil were germinated under optimal conditions in a glasshouse. The number of germinated seeds of R. obtusifolius in case parcels was 866 ±152 m-2 (CH, mean ±SE), 628 ±183 m-2 (SI), and 752 ±183 m-2 (UK), with no significant difference among countries. Densities in individual case parcels ranged from 0 up to approximately 3000 seeds m-2 (each country). Control parcels had significantly fewer seeds, with a mean of 51 ±18, 75 ±52, and 98 ±52 seeds m-2 in CH, SI, and UK, respectively, and a range between 0 and up to 1000 seeds m-2. Across countries, variables explaining variation in the soil seed bank of R. obtusifolius in case parcels were soil pH (negative relation), silt content (negative), land-use intensity (negative), and aboveground R. obtusifolius plant density (positive). Because a large soil seed bank can sustain grassland infestation with R. obtusifolius, management strategies to control the species should target the reduction in the density of mature plants, prevention of the species' seed production and dispersal, as well as the regulation of the soil pH to a range optimal for forage production.
... نتایج نتایج با همسو نظر این از حاضر پژوهش مطالعات (Petrov, 1977) و (Thompson and Grime, 1979) ...
... The main reason could be that in formal urban green spaces, there's a signi cant amount of human management, making it di cult for weed populations to form stable communities.The seed density in urban wasteland exhibits distinct seasonal variation, with seed density in spring being notably lower than that in autumn. Our autumn sampling was in November, when the seeds of most summer annual and perennial plants got mature and many of them forming a transient seed bank with a large proportion of germinable seeds(Thompson & Grime, 1979). The sampling in spring was in April, when the seeds in the transient seed bank have already germinated, resulting in a lower seed density.Our study found that the seeds bank of wasteland in Shanghai are dominate by annuals plants and small growth type species. ...
Urbanization greatly impacts both the diversity of soil seed banks and the spatial dynamics of species. These seed banks, which hold seeds from current and past vegetation, are vital in shaping future plant diversity. They also serve as a window into the ecological history and potential for recovery in urban wastelands, which are continually evolving due to urbanization. In this study, we focused on the soil seed bank of wasteland in Shanghai China, by selecting 24 plots along urban-rural gradients. Soil samples were collected from each plot for seed bank germination experiment in both spring and autumn. We tested whether the seed density, species diversity, and composition of soil seed banks in wasteland varied along an urban-rural gradient. The results showed that seed density was higher in autumn than that in spring and no significant difference was found along urban-rural gradients. A total of 75 species, belonging to 26 families and 69 genera, was recorded in soil seed banks, in which annuals were the dominant life form and autochory was the dominant dispersal model. The proportion of exotic species was nearly 40%. There is no significant difference along urban-rural gradients for functional composition (i.e. the proportion of annual plant species, small growth type species, exotic species, and dispersal modes), species diversity (i.e. richness and Shannon-Wiener index), and species composition, excepting that marginal significant for autumn species composition among urban-rural gradients. The relative homogeneity in the seed bank across urban-rural gradients may primarily be due to the young age of the wastelands.
... Las especies formadoras de bancos de semillas permanentes (duración de un año o más, semillas con viabilidad por largos periodos de tiempo, Thompson y Grime, 1979), pueden ser utilizadas en programas de restauración pasiva, especialmente en hábitats donde el disturbio es impredecible, por lo que la presencia de propágulos de especies secundarias en estas fuentes de regeneración es sumamente importante. La restauración activa (a través de la adición de semillas con intervención del humano) será más importante en hábitats sujetos a pocos disturbios en los cuales el uso de especies que forman bancos de semillas transitorios (de poca duración, menos de un año, semillas con tiempos cortos de viabilidad) es lo más recomendable. ...
Los humanos hemos incidido cada vez más en la pérdida de los recursos naturales y de la funcionalidad de los ecosistemas. Por lo que, entender la trayectoria de los cambios ante las perturbaciones antropogénicas en los bosques es un gran desafío. La resiliencia describe la capacidad de un ecosistema para resistir y recuperar sus componentes después de una perturbación. Sin embargo, resulta complejo medir la resiliencia en sitios donde los disturbios son recurrentes, por lo que este capítulo, aborda la importancia de conocer la estructura, composición y función de la vegetación secundaria en un bosque inmerso en una gran ciudad. El objetivo es evaluar su persistencia, trayectorias de cambio y describir los atributos biológicos de especies de la vegetación secundaria que pueden utilizarse como indicadores e incidir en la planeación estratégica de recuperación y manejo.
... The SSB study was carried out using the seedling emergence method, which evaluates the viable seeds in the soil (Thompson and Grime 1979). Germination was considered when the seedlings had a root system, aerial parts, terminal buds, and at least one pair of cotyledons (Brasil 2009). ...
i>Eucalyptus species are cultivated for various purposes around the world, mainly because they adapt well and grow quickly. These productive matrices of planted forests are common in Brazil, added to which, areas of native vegetation are requirements of environmental legislation. Although eucalyptus plantations are widely distributed in Brazil, little is known about the soil seed bank (SSB) in the eucalyptus productive matrix (EPM). We aim to understand how the EPM made up of eucalyptus plantations and native forest remnants affect the SSB in the Brazilian Pampa. Samples of the SSB of EPM were collected and monitored for six months in a shade house. We evaluated seedling emergence, richness, composition, ecological characteristics of the species, diversity, and floristic similarity. We recorded a high rate of seedling emergence, species richness, and different life forms and native species in all EPM treatments, however the similarity between native remnants and eucalyptus plantations was low. The size and level of conservation of native remnants and the position and management of eucalyptus sites in the EPM influenced the diversity and composition of species. Eucalyptus plantations contain SSBs with potential for natural regeneration when they are in a landscape that maintains conserved native forest remnants. These results expand the knowledge of the SSB in EPM and can support actions in ecological restoration projects.
... Some studies believe that the density of soil seed banks in grassland is positively correlated with the density and coverage of the aboveground vegetation community . The results of this study showed that the density of temporary soil seed banks in grassland habitats showed a significant positive correlation with the density of aboveground plant community, while the density of temporary soil seed banks and permanent soil seed banks in desert and meadow habitats showed an increasing trend with the increase of aboveground vegetation density, but the difference was not significant, which was compared with Harper (1977), Thompson and Grime (1979), Coffin and Lauenroth (1989) and other researchers think that there is no obvious correlation between the grassland aboveground vegetation density and the soil seed bank density. The results are similar. ...
... y Epithelantha micromeris F.A.C. Weber ex Britton & Rose (Maiti et al., 1994), . Las especies con semillas pequeñas o medianas, a diferencia de con semillas grandes, tienen una mayor probabilidad de escapar de los granívoros y de permanecer en el suelo, y por ende pueden tener una mayor probabilidad de formar un banco de semillas por más de un año (Thompson y Grime, 1979;Rojas-Aréchiga y Batis, 2001;Rojas-Aréchiga et al., 2013). ...
Antecedentes y Objetivos: La capacidad de formar un banco de semillas es una de las estrategias que permite la regeneración poblacional de especies en ambientes impredecibles. El fotoblastismo positivo, la longevidad ecológica, el tamaño de la semilla y mecanismos de latencia suelen ser atributos de las semillas que forman bancos. En este estudio evaluamos el efecto de la edad de las semillas en la germinación y supervivencia de Lophophora diffusa, una cactácea de la región del Semidesierto Queretano-Hidalguense, con el objetivo de reconocer su potencial para formar un banco de semillas. Métodos: Se desarrolló un diseño experimental teniendo como factor la edad de las semillas, con semillas colectadas el año que se realizó el experimento (2018) y semillas de cuatro años (colectadas en 2014). Se registró la germinación y la supervivencia de las plántulas en 15 tiempos de observación cada tercer día. Los resultados de germinación se analizaron mediante un modelo de “tiempo al evento” con un ajuste de función log-logística y se realizó una prueba de t para determinar diferencias entre los parámetros estimados. Los resultados de supervivencia se analizaron mediante un modelo lineal generalizado con distribución de error binomial y función de enlace-logit. Resultados clave: Aunque las semillas de mayor edad presentaron un tiempo medio de germinación superior en comparación con las de menor edad, la edad de las semillas no afectó la germinación, ni la supervivencia de las plántulas. Las semillas estudiadas permanecen viables en condiciones de laboratorio hasta cuatro años, con porcentajes de germinación y supervivencia >50% independientemente de la edad de las semillas. Conclusiones: La capacidad de las semillas de mantenerse viables hasta por cuatro años en condiciones de laboratorio, sumada a las características morfológicas y fisiológicas conocidas para esta especie, indican su potencial de formar un banco de semillas persistente de corto plazo.
... The ability of plants to effectively compete with others in their native community is also dependent on their seed viability and seed bank density. A seed bank may either contain seeds that are viable in the soil for less than a year (transient) or seeds that remain viable in the soil for a long period (persistent) (Thompson and Grime 1979). The persistent seed bank is further classified as short-term persistent (seeds remain viable in the soil for 1 -5 years) and long-term persistent seed banks (seeds remain viable in the soil for over 5 years) (Walck et al. 2005). ...
The assessment of seed banks could provide useful hints towards ensuring restoration planning and invasive species management. In this study, the impacts of two invaders, Hyptis suaveolens and Urena lobata on the soil seed banks were investigated. We also assessed the seed characteristics of the invaders at the invaded sites. This was achieved using 10 sites each for H. suaveolens, U. lobata invaded habitats and non-invaded habitats making a total of 30 sites. We collected 200 soil samples in each habitat type. A seedling emergence method was used to determine the seed bank recruitment of both invasive plants. The diversity indices of the above-ground vegetation of sites invaded by the two plants were significantly lower than those of the non-invaded sites. Only two plant species emerged from the seed banks of H. suaveolens and five plants from those of U. lobata as compared with non-invaded sites where 53 species emerged. A larger portion of the seeds was located in the soil's lower layer at all the sites invaded by H. suaveolens while those of U. lobata and non-invaded sites were found in the upper layers and there are significant associations between the habitats . The lower soil layers of the two species have the highest percentage of viable seeds. These results help to understand more about the invasiveness of both species as related to their impacts on the seed banks and native vegetation. It also indicates that the native species that emerged from the invaded seed banks could be used for the restoration of the invaded habitats.
... Soil diaspore banks contain the accumulated number of species over years. Thus, the number of species is much higher than the actually emerged number of species during a vegetation period, which is why a higher sampling effort is needed for the soil diaspore bank (longer increase of the curve) (Thompson and Grime, 1979). However, it remains to be considered that the results of the species accumulation curve could depend on the spatial scale. ...
... Since a large proportion of weed seeds germinate or die within 1 to 4 years, this pool was named the short-term seed bank and the rest, which survives 5 years or more, long-term seed bank. In another system, four types of species, according to their life cycle and survival strategy in the soil seed bank, are distinguished (Thompson and Grime, 1979). The seed bank of a particular species is transient when no seed remains alive for more than one year. ...
The soil seed bank could be viewed as an optimisation of the chances of plants to meet favourable conditions in time and space. Owing to the large number of publications and the field’s complexity, available reviews do not cover the entire field. My objective was to produce a synthesis. Determination of the soil seed bank needs careful planning of sampling because of variations in soil depth and clumped distributions. Sample composition is determined from plantlets coming from germinated seeds after exposure to appropriate conditions or directly from seeds after their separation from soil particles. Seed longevity varies from months to decades and depends on desiccation resistance, defences against predators and germination control, notably dormancy. Dormancy characterisation and alleviation factors allow to understand species’ strategies in ecosystems. In agricultural soils, weeds challenge future cultures. Research objectives are often to exhaust their seed banks before crop emergence by reducing seed production, inactivating germination, removing weeds before seed maturation, and controlling the harvest. In natural ecosystems, climax species tend to produce shorter-lived seeds compared to pioneered ones. The soil seed bank may help in restoring degraded vegetation but the similarity with the aboveground vegetation is low. Disturbances may increase or decrease the soil seed bank diversity. Restoration may often rely on natural recruitment from undisturbed areas or on artificial translocation. I emphasise the need to integrate soil seed bank knowledge into dynamic vegetation models, which generally lacks most of the soil seed bank features, while the future distribution of the plant species is one of the main questions in this climate change era.
... We used the standard seedling emergence by germination method (Thompson and Grime, 1979) to determine what seeds were in the soil and how simulated climate change affects their germination. This method is the most commonly used to study soil seed banks and generally produces germination rates between 81 and 100 % of the viable seeds present in the soil (Ter Heerdt et al., 1996). ...
Background and Aims
Seed persistence in soil depends on environmental factors that affect seed dormancy and germination, such as temperature and water availability. In high-elevation ecosystems, rapid changes in these environmental factors due to climate change can impact future plant recruitment. To date, our knowledge on how soil seed banks from high-altitude environments will respond to climate change and extreme climate-related events is limited. Here, using the seedling emergence method, we investigated the effects of reduced snow cover, fire and drought on the density and diversity of germinants from soil seed banks of two high-altitude plant communities: a tall alpine herbfield and a treeline ecotone.
Methods
In Autumn 2020, we collected soil samples and characterized the standing vegetation of both communities at Kosciuszko National Park, Australia. Then, we employed a factorial experiment and subjected the soil samples to a series of manipulative treatments using greenhouse studies.
Key results
The treeline had a larger and more diverse soil seed bank than the herbfield. A reduction in snow had a negative effect on the number of germinants in the herbfield and increased the dissimilarity with the standing vegetation, while the treeline responses were mainly neutral. Fire did not significantly affect the number of germinants but decreased the evenness values in both communities. The drought treatment reduced the number and richness of germinants and increased the dissimilarity with the standing vegetation in both communities. Plant functional forms explained some of the detected effects but seed functional traits did not.
Conclusions
Our study suggests that simulated climate change will affect plant recruitment from soil seed banks in a variety of ways. Changes in snow cover, incidences of fire and drought may be key drivers of germination from the soil seed bank and therefore the future composition of alpine plant communities.
... A total of 576 soil samples were collected (six species × six individuals per species × two sites × four SSB samples × two reproductive seasons). The indirect (or seedling emergence) method was used in the first stage of analysis (Thompson and Grime, 1979;Dalling et al., 1995;Ferrandis, 2019). For that, the samples were arranged in the same trays that were sampled in the field. ...
Soil seed banks (SSB) are reservoirs of viable mature seeds that play a crucial role in the dynamics and recovery of vegetation following disturbances. Despite its importance, there is still limited understanding of their characteristics of SSB in semiarid subtropical ecosystems. Our objective was to evaluate the effects of wildfire and roller-chopping on the size and persistence of the SSB of six native woody species, considering the influence of seed functional traits (FT). This study was conducted in dry subtropical forests of the western Argentine Chaco region. We evaluated SSB of six woody species: Aspidosperma quebracho-blanco (Aqb); Schinopsis lorentzii (Sl); Sarcomphalus mistol (Sm); Senegalia gilliesii (Sg) and Vachellia aroma (Va) in experimental plots located in two sites (forest plots of ca. 5 ha): forests without disturbance within the last four decades (conserved forest-CF) and forests subjected to fires and mechanical treatments for the partial removal of the shrub layer (roller-chopping and burned forest-RBF). Samples of the SSB were taken under the canopy of six focal individuals of each species in two reproductive seasons between 2016 and 2018. Seeds from ten mature trees of each species were collected to characterize their functional traits (shape and seed mass) related to their aptitude to form the SSB. Three groups of species were identified based on FT analysis: I-large, compressed seeds (Sl, Aqb and Sg); II-medium-size subspherical seeds (Va and Nn); and III-large spherical seeds (Sm). Aqb, Sl, Nn, and Va presented significant differences in the size of their SSB when comparing between sites and sampling years (p = 0.0013; p = 0.0006; p = 0.0020; p = 0.0151, respectively), but no clear patterns emerged among them. The SSB from Aqb and Va were greater in RBF than in CF, only during the second sampling season (105.3 ± 35.2; 352.6 ± 133.4 seeds.m − 2 , respectively). Sl also exhibited the highest SSB (97.7 ± 30.5) in the second year of sampling, while Nn showed the largest SSB in the first year, (1569.0 ± 847.0 seeds.m − 2), both within CF. Finally, Sm and Sg did not present significant differences in their SBB between sites and years. We concluded that all studied species form transient SSB and that the shape index type II favors seed burial, so increasing SSB size and viability. Forest disturbances differentially affect the SSB of woody species in the dry subtropical Chaco because some species decreased, increased or showed no effects during different reproductive seasons. Thus, the potential long-term influence on the dynamics and resilience of dry forests in the subtropics needs to be monitored in the long term.
... Soil samples were collected on 1 July 2017, after autumn-winter-spring germination and before the start of seed dispersal from fruits produced that year. This sampling date was determined based on the concept of a persistent seed bank [31] in order to quantify the persistent fraction of the seed bank overlapping two consecutive phenological cycles. ...
Members of the genus Atropa contain various tropane alkaloids, including atropine ((±)-hyoscyamine) and scopolamine, which possess medicinal properties. Preserving the diverse genetic background of wild populations via optimal plant production from seeds could be essential for avoiding the loss of potential uses. We analyzed the germination ecology of two Atropa species comprising the threatened A. baetica and widespread A. belladonna to determine the: (1) influence of temperature, light, and seed age on germination patterns; (2) effects of cold stratification and gibberellic acid (GA3); (3) phenology of seedling emergence in outdoor conditions; (4) phenology of dormancy break and loss of viability in buried seeds; and (5) ability to form persistent soil seed banks. Freshly matured seeds exhibited conditional physiological dormancy, with germination at high temperatures (32/18 °C) but not at low and cold ones (5, 15/4, 20/7 °C). The germination ability increased with time of dry storage and with GA3, thereby suggesting nondeep physiological dormancy. Under outdoor conditions, no seedlings emerged during the first post-sown autumn, but emergence peaks occurred in late winter–early spring. Both species could form small persistent soil seed banks with short durations (3–5 years). A plant production protocol from seeds was established for both taxa.
... Soil seed bank sampling was conducted on 2 July 2017, approximately 3 weeks before seed dispersal began and after seedling emergence. The sampling season was determined based on Thompson and Grime's (1979) concept of a persistent soil seed bank. Sampling was conducted in 20 randomly located plots measuring 1 m 2 . ...
Background Many studies have focused on the dormancy-breaking response to heat treatment of freshly matured seeds and immediately after thermal shock. Aims We evaluated whether the full effect of dry heat scarification in freshly matured seeds could be delayed over time and the possible influence of previous storage in the soil. Methods Adenocarpus argyrophyllus was the model species selected to explore our hypotheses by analysing the: (a) influence of scarification treatments; (b) seedling emergence during 5 years after dry heat scarification of freshly matured seeds, and evaluating intrapopulation variation; (c) seedling emergence after dry heat scarification of seeds rescued from soil; and (d) ability to form persistent soil seed banks. Key results Dry heat scarification of freshly matured seeds only resulted in 22.5% germination. However, exposure to pre-sowing thermal shock stimulated seedling emergence during the first few years post-planting, with high intrapopulation variation. In seeds recovered from soil, thermal shock before reseeding increased the seedling emergence rate. Conclusions and implications Our results show that, to avoid incomplete interpretation, studies of thermal treatment on the breaking of physical seed dormancy should allow the seeds sufficient time to exhibit the complete effects of high temperature treatment, thereby preventing underestimation.
... The seedling emergence approach was selected because it allows an estimate of the viable portion of the seed bank and enables the identification of the seed flora to species level, although it may fail to detect a portion of the dormant flora whose germination requirements are not met under greenhouse conditions (Thompson and Grime 1979). Soon after collection (in May 2018 for the spring samples and November 2018 for the autumn samples), soil samples were processed before transferring them to pots, and seedling emergence was monitored on a weekly basis for one year for both sets of samples. ...
Introduced plants can have long-lasting and irreversible effects on the communities and ecosystems they invade. A critical step towards understanding the legacy of plant introductions is the characterisation of changes in the invaded plant communities and how these changes are related to biogeochemical modifications. Here, we addressed this issue by comparing the impacts of two large invasive herbs, Gunnera tinctoria and Impatiens glandulifera , on the compositional, functional, and phylogenetic structure of the standing vegetation (above-ground communities) and the soil seed bank (below-ground communities). The introduction of both invasive species was associated with a significant decrease in above-ground species richness, with subsequent changes in the functional diversity and phylogenetic dispersion of the vegetation. Yet, these invaders differed in their long-term impacts and the reversibility of any modifications they caused. While G. tinctoria invasions resulted in phylogenetically clustered communities (both above- and below-ground) that were clearly distinct from uninvaded ones, seed bank communities invaded by I. glandulifera were indistinguishable from uninvaded ones, despite major compositional changes above-ground. Further, we found alterations in nutrient cycling associated with G. tinctoria invasions that could facilitate its local persistence and exacerbate any negative effects on native diversity. Our findings suggest a high susceptibility of pre-invasion above-ground communities to colonisation by distantly related herbs. However, the seed banks showed a degree of resilience against both invaders, with no major differences in species richness. Ultimately, differences in the impacts of these large invasive herbs suggest that dominance in the vegetation and a large stature are poor predictors of long-term plant community changes, including regeneration potential from seed, which are associated with plant introductions.
... According to Pyšek and Richardson [46], invasive species germinate earlier, more quickly, and/or over a wider range of environmental conditions than native or noninvasive ones, which provides a competitive advantage [47][48][49]. However, in volatile environments, forming a seed reservoir may be a better strategy for invasive species as the buried seeds can ensure the persistence of the species while mitigating competition [2,50,51]. Glossy buckthorn seeds require cold stratification, germinate better in light, and when scarified achieve greater germination rates at mild temperatures which are known to delay germination and promote seed burial [7,52]. Glossy buckthorn seeds are known to form seed banks that can remain viable in the soil for up to three years [18]. ...
Understanding seed characteristics, germination, and seedling establishment patterns is essential for formulating effective management strategies to control invasive species. Glossy buckthorn (Frangula alnus) is a shrub or small tree from Eurasia that has become invasive in North America, and which has negative impacts on plant communities and ecosystems. In this study, we analyzed the germination response of glossy buckthorn seeds to different temperatures (12, 14, 16, 18, 20, 24, and 28° C), various stratification lengths (4 to 20 weeks), and scarification conditions to measure the impact on breaking seed dormancy, and the effect of light in triggering germination. Analysis using distinct time-to-event approaches, including the Kaplan–Meier estimator and Cox proportional hazard model, was employed to interpret germination data. Glossy buckthorn seeds exhibited physiological dormancy and required cold stratification to germinate. At 12° C, only 14% of the seeds could germinate. At warmer temperatures, germination rates increased, reaching a peak of 70% at 20 °C. At 24° C and 28 °C, germination declined, and seeds were probably induced into secondary dormancy. Scarified seeds had a higher probability of germination than non-scarified ones, even at the lowest temperatures. Darkness had a negative impact on germination at all tested temperatures. This study significantly advances our understanding of how temperature, light, stratification, and scarification impact glossy buckthorn seeds, elucidating the species’ seasonal germination patterns in North America. The results emphasize that glossy buckthorn utilizes seed banks as a primary strategy for invading and establishing in new habitats. The ungerminated seeds form persistent seed banks, ensuring F. alnus’ survival and bolstering its chances of successful establishment and invasion. As climate change drives temperature increases, it may affect seeds in the soil, altering stratification periods and consequently shifting the timing of germination.
... Soil seed banks represent the reservoir of viable, persistent seeds stored in the soil to provide natural regeneration and restoration of degraded areas (Roberts 1981;Christoffoleti & Caetano 1998). Persistent soil seed banks represent seeds that can persist in the soil and include an accumulation of seeds from many years (Thompson & Grime 1979). By providing primary sources for ecosystem succession, persistent seeds in the soil are responsible for maintaining the regeneration capacity of annual species after natural death and when perennial species face various diseases and disturbances (Baker 1989). ...
The soil seed bank is an essential source for the natural restoration of degraded rangelands. This study assessed seed density and species composition of soil seed banks in plots where grazing had been excluded by fencing for six years and in control plots in Auðkúluheiði and Þeistareykir in the highland rangelands of Iceland. Soil samples were collected from 48 experimental plots at 0-10 cm depth. Emerged species from the soil seed bank (belowground) were compared with existing vegetation (aboveground). Only 48 seedlings from 15 species emerged from the soil samples. The results showed a negligible correlation between species richness in the aboveground vegetation and the number of seedlings that emerged from soil seed banks. The number of emerged seedlings did not significantly differ between fenced and control plots. However, the species richness of the soil seed banks in the non-fenced plots was higher than in fenced plots, and this was mirrored by higher species richness in non-fenced plots in the aboveground vegetation. The results of this study indicate that six years of grazing exclusion in the Icelandic highlands might not be long enough to drive differences in the soil seed banks, suggesting that grazing exclusion may not be an efficient short-term strategy to strengthen soil seed banks in rangelands that have been grazed for centuries. GRÓ Land Restoration Training Programme ii
... In January and May 2020, four soil samples of 250 mL were taken from each of the 18 plots in their four corners, at the edge of the vegetation survey area in order to, respectively, survey the winter seed bank (which contains the permanent and semi-permanent seed bank, i.e., seeds that can remain viable in the soil for many years and sometimes decades) in January and the spring seed bank (which contains in addition, the transient seed bank, i.e., seeds that persist in the soil for a relatively short period of time, usually less than one year) in May [34]. ...
Extensive green roofs are well known to improve the urban environment, but in the Mediterranean regions, dry climatic conditions pose the problem of their sustainability when no irrigation is applied. After planting or sowing in 2012, 18 local Mediterranean plant species on different types of exposure and substrate in a non-irrigated extensive green roof in Avignon (South-Eastern France), the physico-chemical characteristics of the soil, winter and spring soil seed banks, soil mesofauna and initially sown, planted, or spontaneous vegetation expressed on the surface were studied from 2013 to 2020. In 2020, significant differences related to the exposure conditions (shade/sun) and, to a lesser extent, to the depth of substrate used (5 cm/5 cm or 10 cm with a water retention layer) were found. The deeper plots in the shade have significantly higher soil fertility, cover, and vegetation height. However, the plots in the sun have higher moss cover, planted or sowed vegetation abundance, and springtail abundance. By 2020, more than half of the initially sown species had disappeared, except for several planted perennials and short-cycle annual species. On the other hand, a significant increase in the species richness of spontaneously established species was measured over time. In the absence of a permanent and transient seed bank for the sowed and spontaneous species, the plant community is then mostly dependent on species flows via the local surrounding seed rain. Planting perennial species (Sedum spp., Iris lutescens), followed by spontaneous colonization of species present in the vicinity of the roof would then represent a more efficient strategy for the persistence of extensive non-irrigated green roofs in Mediterranean environments than sowing a species-rich local Mediterranean seed mixture dominated by annual species.
... To describe the structure of the soil seed bank in tall fescue-invaded and uninvaded areas, we used the seedling emergence approach (Thompson & Grime, 1979; Appendix S1). To account for cool-and warm-season species, we evaluated the soil seed bank during two seasons. ...
Questions
Restoring diversity in temperate grasslands requires eliminating invaders and recovering different native phenological groups. Clipping and seed addition promote native grass recovery, but these effects could depend on the phenological overlap between invaders and native species. We evaluated the importance of the interaction between two types of clipping, species phenology and sowing to restore temperate grasslands invaded by the cool‐season forage species Festuca arundinacea (tall fescue).
Location
Flooding Pampa grassland (Buenos Aires, Argentina).
Methods
We applied selective and non‐selective clipping on tall fescue during the peak growing season, combined with the sowing of native cool‐ and warm‐season grasses. Plant species cover was estimated visually for 3 years; species were categorized by functional groups. Moreover, through emergence trials, we evaluated whether the soil seed bank had been impoverished by invasion.
Results
Regardless of selectivity, clipping decreased tall fescue cover by 12%/year, which reduced microsite limitation. Consequently, total native richness increased by 5 spp./year and cover increased from 3% to 50% by the last experimental year, independent of clipping type. Moreover, native warm‐season grasses, the group with the least phenological overlap with invaders, increased by nearly 25% in cover and by 5 spp./m ² with clipping and independently of sowing. Contrarily, native cool‐season grasses, with more phenological overlap with invaders, increased 5% with propagule addition. Furthermore, the seed bank was enriched with tall fescue and depleted of cool‐season grasses.
Conclusions
Our results reveal that overcoming microsite limitation is a necessary condition to restore plant diversity in grassland invaded by tall fescue. Nevertheless, seed limitation and phenological overlap may be particularly important to restore the diversity of some native functional groups of plants. Considering the phenology of species can help to identify either clipping targets or phenological groups to be sown when restoring native diversity.
... Previous studies have indicated that increases in grazing intensity generally enhance vegetation species richness (Gao and Carmel, 2020;Moinardeau et al., 2020), particularly in areas with high rainfall (Gao and Carmel, 2020). This increase in vegetation richness includes the emergence of new vegetation species, which most likely resulted from the soil seed bank breaking seed dormancy (Thompson and Grime, 1979;Moinardeau et al., 2020). Thus, livestock grazing might increase the likelihood of dormancy breaking of vegetation's seeds, especially for grasses (Zida et al., 2020). ...
CONTEXT. Prolonged use of synthetic herbicides to control weeds may cause adverse effects on the environment and human wellbeing. As a mitigation effort, commercial oil palm growers have been encouraged to adopt livestock integration as a holistic approach to manage weeds. Previous studies have suggested utilizing a multi-species livestock grazing may optimize the grazing impacts in silvopastoral agroforestry systems. OBJECTIVE: Present study examined the effects of small ruminant grazing (i.e., goats, sheep and multi-species) on undergrowth vegetation with the following specific objectives: 1) to investigate the effects of small ruminant grazing treatments on undergrowth vegetation composition in oil palm plantations; 2) to examine the variables (canopy cover, grazing treatments, and cycles) that influenced undergrowth vegetation (species richness, coverage, height, and dry weight) in oil palm plantations. METHODS: We established quadrats on experimental plots to detect changes in undergrowth vegetation composition, species diversity, coverage, height, and dry weight resulting from different grazing treatments. RESULTS AND CONCLUSIONS: We found that undergrowth vegetation composition varied between different grazing treatments. The multi-species livestock grazing effectively supress unwanted weeds (i.e., woody broadleaves) compared to single–species livestock grazing (i.e., goats, sheep). The use of single-species livestock grazing is likely to cause oil palm growers to use herbicides to control undesirable weeds. Hence, we concluded managing undergrowth vegetation in oil palm plantations using multi-species livestock grazing is a practical approach, and it should be fine-tuned for example by choosing livestock species based on the targeted objectives and the grazing sequence that will be practiced to regenerate the oil palm silvopastoral system. SIGNIFICANCE: Multi-species livestock grazing can reduce oil palm growers' dependence on synthetic herbicides for weed control and optimize land use in oil palm plantation sector. On the other hand, the use of single species, whether goat or sheep-only, has caused unwanted undergrowth to increase after several grazing rotations have been carried out. Therefore, the use of multi-species grazing is a promising biological tool to reduce synthetic herbicide application in environmentally-sustainable oil palm plantations.
... Diaspores form genetic archives of successive generations, encapsulating phenotypic variation produced under variable environmental conditions (Hock et al. 2008). This maintains genetic diversity and persistence in habitats when faced with variable conditions through time (Thompson and Grime 1979;Frey and Kürschner 2011). ...
... There are some species with persistent seed banks in which most seeds germinate quickly, but some survive for at least one year. In contrast, other species with persistent seed banks have only a few seeds germinating soon after dispersal [70]. Dormancy regulates the persistence of weed soil seed banks and the timing of seedling emergence [71]. ...
Many weeds produce dormant seeds that are unable to complete germination under favourable conditions. There are two types of seed dormancy: primary dormancy (innate dormancy), in which seeds are in a dormant state upon release from the parent plant, and secondary dormancy (induced dormancy), in which dormancy develops in seeds through some experience after release from the parent plant. Mechanisms of seed dormancy are categorized as embryo dormancy and coat-imposed dormancy. In embryo dormancy, the control of dormancy resides within the embryo itself, and in coat-imposed dormancy, it is maintained by the structures enclosing the embryo. Many factors can influence seed dormancy during development and after dispersal; they can be abiotic, biotic, or a combination of both. Most weeds deposit a large number of seeds in the seed bank, which can be one of two types—transient or persistent. In the transient type, all viable seeds in the soil germinate or die within one year, and there is no carry-over until a new crop is deposited. In the persistent type, at least some seeds survive in the soil for more than one year and there is always some carry-over until a new crop is deposited. Some dormant seeds require after-ripening—changes in dry seeds that cause or improve germination. Nondormant, viable seeds can germinate if they encounter appropriate conditions. In the face of climate change, including global warming, some weeds produce a large proportion of nondormant seeds, which germinate shortly after dispersal, and a smaller, more transient seed bank. Further studies are required to explore this phenomenon.
... This suggests that these two species have a strong reproductive and diffusion capacity, enabling them to spread effectively along perpendicular roads between habitats while being less in uenced by differences in habitat characteristics. Additionally, successful invasive alien species often have similar life history strategies, for example, some invasive alien plants can form long-lasting seed banks (Grime 1979), and soil seed bank distribution zones may serve as sources for further invasion. Understanding the characteristics of seed banks associated with invasive alien plants is essential to determine their persistence and invasiveness. ...
Invasive alien plants cause major losses to native biodiversity. Nature reserves are crucial in resisting invasion, but resistance varies by habitats. To explore the variations and factors that determine invasive alien plant dispersal patterns in different habitats, we investigated abandoned land, eucalyptus plantations, and natural secondary forests in Encheng National Nature Reserve, Guangxi. Our results showed a significant decrease in invasive alien plants with increasing distance from roads in secondary forest, while there was no significant trend in the two other habitats. No significant trends were observed in the distribution of invasive alien plants within the soil seed bank in the three habitats perpendicular to the road direction. Invasive alien plant composition varied with the distance from the road and was found to be similar both aboveground and in the soil seed bank. Factors influencing invasive species composition at different road edges differed by habitats, abandoned land was affected by average human flow, average traffic flow, and distance to the village, eucalyptus plantations by pH, average human flow, native herb richness of soil seed bank, and road width, and secondary forest by road width, road grade, and native herb richness and density. Our results indicated that the secondary forest resists plant invasion better than eucalyptus plantations and abandoned land, moreover, native herbs play important roles in resisting invasive species in both secondary forest and eucalyptus plantations. To target invasive alien plants in nature reserves, prioritize the abandoned land and plantation forests based on our findings.
... The soil seed bank which designates the stock of viable seeds in the soil (Garwood, 1989;Roberts, 1981;Savadogo et al., 2016) plays an important role in the maintenance of the ecological diversity of natural ecosystems (Brown and Venable, 1986;Houle and Phillips, 1988;Saatkamp et al., 2014;Thompson and Grime, 1979). Recruitment from transient or persistent soil seed banks has long been considered an important pathway for regeneration of tropical pioneer species (Dalling et al., 1998;Hall and Swaine, 1980). ...
This thesis deals with drivers of forest regeneration in central African moist forests.
More specifically, this work focuses on the role of the soil seed bank in the regeneration of these forests knowing that there is an important lack of relevant information on this subject. The study aims to : (i) assess the abundance and floristic composition of the soil seed bank of two forest types growing on different soil; (ii) quantify the abundance of the soil seed bank of an important timber species (Erythrophleum suaveolens), and study the factors involved in the breaking of its seeds dormancy; (iii) evaluate the ability of the near infrared hyperspectral imaging system in discriminating seeds of two sister species, E. suaveolens and E. ivorense.
... The other methods involves seedling emergence (INHF, 2001, Anyanwu, et al., 2019. The seedling emergence method involves the placement of soil samples under suitable conditions for seed germination (i.e., greenhouse or germination chamber); then, the emerging seedlings are identified and counted (Thompson and Grime 1979). The seedling emergence method is less relentless and helpful for a huge volume of soil tests (Plue et al., 2012). ...
Soil seed bank of three scrap metal dumpsites were assessed for weed composition in River State Nigeria. Soil samples were acquired from nine locations in the three communities comprising studied; six scrap metal dumpsites and three control sites at three varying depths (0-5cm, 5-10cm and 10-15cm plates, each containing 100g soil were cultured and monitored for seedling emergence, species composition and abundance for 12 weeks. Soil physical and chemical properties and heavy metal (copper, zinc and lead) composition of soil samples were determined following standard procedures Result were statistically analysed using ANOVA at P=0.05. The results shows that control site had the highest number of emergent seedling and was significantly different P<0.05 from the scrap metal sites at all depts except in Aluu scrap metal at 10-15cm. Control had the highest weed seed population particularly at 0-5cm depth. Copper, zinc and lead were present at all scrap metal sites. Consequently, the scrap metal had potential detrimental effects on the soil seed bank population in all the locations assessed.
... Three replicate soil samples were also collected each at depths of 0-15 cm and 15-30 cm, taken to the Laboratory of the Department of PSB and air-dried. The soils were filled into perforated plastic pots and the direct germination method of Thompson and Grime (1979) was used to assess the readily germinable seed species composition. The relative abundance of plant species or families on the standing vegetation and seed bank was estimated as the percentage each species or families contributed to the total number of individuals present. ...
In Nigeria, Chromolaena odorata (L.) R. M. King and H. Rob and Tithonia rotundifolia (Mill.) S. F. Blake, are exotic invasive weeds, but a gradual decrease in the population of C. odorata with the rapid invasion of T. rotundifolia is now observed. Therefore, this study investigated the adaptive features of each weed in competition, with a further determination of seedling recruitment from the soil seed bank of plots invaded by T. rotundifolia. Field sampling was carried out in 10 plots: T. rotundifolia invaded plots and low or uninvaded plots in co-existing with other plants using 10 m x 10 m quadrats. The readily germinable seed species composition and the Sorensen index of similarity between the seed bank and their above ground vegetation were determined. Competition Series Experiment was also conducted for the two plants. Mariscus alternifolius (227) and Oldenlandia corymbosa (358) were the most abundant species in the seed bank while T. rotundifolia recruited 25 individuals. Low similarity index existed between the seed bank and the standing vegetation of the invaded and uninvaded plots. T. rotundifolia had improved growth in heteroculture with C. odorata over when in monoculture. However, a reduction in growth of C. odorata occurred when in competitive association with T. rotundifolia compared to when in monoculture. T. rotundifolia had competitive advantage over C. odorata.
... The collection of viable seeds within the soil (hereafter "seed bank") can represent both the history of a site and the future pool of propagules available for recruitment and establishment to the aboveground vegetation (Faist et al., 2013). Seed banks can be transient (having seeds that remain viable in the soil for a year or less) or persistent (having seeds that can remain viable in the soil for more than one year) (Thompson & Grime, 1979;Walck et al., 2005). This local seed supply can be impacted by fire through direct burning of vegetation or seeds in the soil, or indirectly by limiting dispersal from nearby sites, especially in larger fires (Pyke et al., 2010). ...
Abstract It is well documented that the recovery of dryland plant communities following wildfire can be variable, and that legacies of fire can have long‐lasting effects on aboveground plant communities. However, our understanding of the degree to which dryland soil seed banks, or the viable seeds in situ, are impacted by fire and their subsequent postfire succession remains extremely poor. To address this important knowledge gap, we used a time‐since‐fire approach to investigate soil seed bank community changes approximately 15 and 30 years after wildfire and to determine the influence of microsites (e.g., shrub vs. interspace) on seed bank composition. We assessed soil seed bank metrics across four North American deserts, including two cold desert sites (Colorado Plateau and Great Basin) and two warm desert sites (Chihuahuan and Sonoran). In greenhouse emergence trials, we found that seed bank characteristics diverged between warm and cold desert sites, such that warm desert sites had seed banks dominated by annual plants while our cold desert sites had seed banks with greater proportions of perennial species, regardless of fire history. In cold desert sites, fire significantly altered seed bank species composition even 30 years after fire. Shrub versus interspace microsites had no observed influence on seed bank composition in any desert. However, seed bank species richness was greater under shrubs in both warm deserts. Non‐native species were present in the seed banks of all deserts and some were particularly abundant in the burned sites. Despite the presence of native species in both burned and unburned seed banks, the presence of non‐native species suggests some degree of vulnerability to future disturbances because fire can create amplifying feedback with many non‐native plants. Our results highlight strong differences in fires' relationship with seed banks for warm and cold desert sites and lend insight into how fire relates to the composition and diversity of the seeds that play a fundamental role in future plant communities.
... Seed density was estimated by the seedling emergence method. This technique is considered effective for assessing both the transient and persistent components of the seed bank (Thompson and Grime 1979). The surface of the soil was cleared off the existing live plant parts, litter, debris, etc. before the collection of soil samples. ...
The natural and semi-natural ecosystems of dry tropical regions are characterized by a high biodiversity with the new introduction of alien invasive species, especially at disturbed sites. The tropical regions due to favorable environmental conditions are considered rich reservoirs of much of the biodiversity of the earth. The Indian dry tropical urban region has also been reported to be highly diverse but fragile with abundant alien flora, of which American, Asian, and European and Asian species form the major contributions. By the allelopathic activity, these weeds alter the soil environment, cause low productive systems with weak soil microflora and accelerate their fast spread by fast colonization, fast reproduction, or highly competitive ability. These weedy species have a great potential to make persistent soil seed banks. The soil seed bank is a reservoir of viable but ungerminated seeds and acts as a genetic reservoir that could play an important role in determining the future vegetation of the community. The present study carried out four different land use patterns and focused on the seed bank dynamics of these sites. In this study, the abundance of alien invasive species in the floristic composition and density of the subterranean vegetation reflects the impact of disturbance and other anthropogenic factors.
Questions
Fire is an important ecological factor influencing plant communities in many fire‐prone ecosystems. Savannas in the Cerrado are resilient to fire, with plants exhibiting fire‐related traits, allowing them to persist in post‐fire environments. Therefore, excluding fire may result in changes in plant community dynamics, thus affecting their resilience. We investigated the effect of the reintroduction of fire in savannas where fire has been excluded for longer periods (>12 years) on seedling recruitment. We asked the following questions: (i) how does fire affect seed bank germination in sites with different fire histories; and (ii) how did fire exclusion affect species composition of the seed bank?
Location
Estação Ecológica de Itirapina (EEI), Southeastern Brazil.
Methods
Two sites with different fire histories were selected: FE1985 – fire exclusion for more than 30 years, with one fire event in 1985; and FE2009 – fire exclusion for 12 years, with three fire events since 1985, the last one being in 2009. Both areas have low fire frequency, but different times since the last fire. Soil samples were collected before and after prescribed fires to evaluate the effects of fire after longer periods of fire exclusion in the soil seed bank. Using the seedling emergence method, we evaluate the effects of the reintroduction of fire after longer periods of fire exclusion in the soil seed bank.
Results
We found that fire significantly increased the seed bank recruitment at both sites, FE1985 and FE2009 (increase of 16% and 50% in seedling recruitment, respectively), showing that species of the Cerrado responded positively to the fire passage. The reintroduction of fire promoted different effects on seed bank recruitment: shrubs experienced a significant decrease in seedling emergence from the seed bank at FE1985, while their recruitment was not affected at FE2009. Time since last fire appears to influence the seed bank composition, showing a shift in dominance from a grassy community to a woody one.
Conclusions
After fire, more species germinated from the seed bank, showing that direct and indirect effects of fire are affecting seed germination from the seed bank, and its importance on seedling recruitment from the seed bank in the Cerrado.
Environmental factors, such as temperature and moisture, and plant factors, such as seed position on the mother plant, can affect seed viability and germination. However, little is known about the viability and germination of seeds in different positions on the mother plant after burial in soil under natural environmental conditions. Here, diaspores from three positions on a compound spike and seeds from two/three positions in a diaspore of the invasive diaspore‐heteromorphic annual grass Aegilops tauschii were buried at four depths for more than 2 years (1–26 months) under natural conditions and viability and germination monitored monthly. Viability of seeds in each diaspore/seed position decreased as burial depth and duration increased and was associated with changes in soil temperature and moisture. Germination was highest at 2 cm and lowest at 10 cm soil depths, with peaks and valleys in autumn/spring and winter/summer, respectively. Overall, seeds in distal diaspore and distal seed positions had higher germination percentages than those in basal diaspore and basal seed positions, but basal ones lived longer than distal ones. Chemical content of fresh diaspores/seeds was related to diaspore/seed position effects on seed germination and viability during burial. We conclude that seeds in distal diaspores/seed positions have a ‘high risk’ strategy and those in basal positions a ‘low risk’ strategy. The two risk strategies may act as a bet‐hedging strategy that spreads risks of germination failure in the soil seed bank over time, thereby facilitating the survival and invasiveness of A. tauschii .
The presence of Cistus species in the soil seed bank in the pasture of the central raña in Cabañeros National Park, which were present in previous plant stages, was investigated. The study was carried out in two steps: firstly, the complete soil seed bank was analysed, from the pasture edge to 100 m towards the raña centre, and secondly, the soil seed bank of woody Cistaceae species was investigated, from 100 to 300 m inland. A long-term persistent highly viable and dormant seed bank of C. ladanifer and C. salvifolius (738 seeds/m2 at 0-10 cm depth) was detected. This seed stock showed a random spatial distribution in the raña. The consequences for the management of the pasture are disccused.
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'Quality of Farmer‐Saved Wheat Seed is Variable in the Southern Great Plains', Crop Management, 5(1), : 1-7 Gharde, Y., Singh, P., Dubey, R. and Gupta, P. (2018) 'assessment of yield and economic losses in agriculture due to weeds in India', crop protection, 107, : 12-18 Hossain, M. 2015. 'recent perspective of herbicide: review of demand and adoption in world agriculture', Journal of the Bangladesh agricultural university, 13(452-2016-35850), : 13-24 Hussain, M. I., Abideen, Z., Danish, S., Asghar, M. A. and Iqbal, K. 2021.'Integrated Weed Management for Sustainable Agriculture', Sustainable Agriculture Reviews 52: Springer, : 367-393 ISWS, G. J. I. C. 2018. 'Fifty Years of Weed Research in India '. ISWS Golden Jubilee ,Internationasl Conference / Fifty years of weed reasearch in India, Jabalpur India, 2018: Indian Society of Weed Science (ISWS)/ ICAR-Directorate of Weed Research (DWR) Maharajpur.Jabalpur- 482 004 India ;Http://WWW.isws.org.in, 357p Javaid, A., R. Bajwa, and T. Anjum, 2008. 'Effect of heat-sterilization and EM (effective microorganisms) application on wheat (Triticum aestivum L.) grown in organic-amended sandy loam soil', cereal research communications, 36(3), : 489-499 Kandasamy, S., N. Weerasuriya, D. Gritsiouk, G. Patterson, S. Saldias, S. Ali, and G. Lazarovits, 2020. 'Size variability in seed lot impact seed nutritional balance, seedling vigor, microbial composition and plant performance of common corn hybrids', Agronomy, 10(2), : 157 Khan, M. B., Asif, M., Hussain, N. and M. Iqbal, 2000. 'Agro-Economic impact of different weed control strategies in wheat', J. Res. Sci, 11(1), : 46-49 Khazaei, F., M., AghaAlikhani, S. Mobasser, , A., Mokhtassi-Bidgoli, H. Asharin, and H. Sadeghi, 2016. 'Evaluation of Wheat (Triticum aestivum, L.) seed quality of certified seed and farm-saved seed in three provinces of Iran', plant breeding and seed science, 73, : 99-115 Kiss, R., O.,Valkó, B. Tóthmérész, and P. Török, 2016. 'Seed bank research in Central-European grasslands-An overview' Lollato, R. 2016. 'Wheat growth and development', Kansas State University Extension Lollato, R., Mark, K., Jaenisch, B. and Haag, L. 2020. 'Wheat Grain Yield Response to Seed Cleaning and Seed Treatment as Affected by Seeding Rate During the 2018–2019 Growing Season in Kansas', Kansas Agricultural Experiment Station Research Reports, 6(5), : 24 Lynch, J. P. 2011. 'Root phenes for enhanced soil exploration and phosphorus acquisition: tools for future crops', Plant physiology, 156(3), : 1041-1049 Michael, P. J., Owen, M. J. and Powles, S. B. 2010. 'Herbicide-resistant weed seeds contaminate grain sown in the western Australian grainbelt', weed science, 58(4), : 466-472 Monaco, T. J., Weller, S. C. and Ashton, F. M. 2002. weed science: principles and practices. John Wiley & Sons, p. 388 Nishimura, A., Asai, M., Shibuya, T., Kurokawa, S. and Nakamura, H. 2015. 'A steaming method for killing weed seeds produced in the current year under untilled conditions', Crop Protection, 71, : 125-131 Norsworthy, J. K., Ward, S. M., Shaw, D. R., Llewellyn, R. S., Nichols, R. L., Webster, T. M., Bradley, K. W., Frisvold, G., Powles, S. B. and Burgos, N. R. 2012. 'Reducing the risks of herbicide resistance: best management practices and recommendations', Weed science, 60(SP1), : 31-62 Oerke, E. 2006. 'Crop losses to pests', The Journal of Agricultural Science, 144, : 31 Owen, M. J. and S. B. Powles, 2020. 'Lessons learnt: crop-seed cleaning reduces weed-seed contamination in Western Australian grain samples', Crop and Pasture Science, 71(7): 660-667 Pinto, J. G. C. P., Munaro, L. B., Jaenisch, B. R., Nagaoka, A. K. and Lollato, R. P. 2019. 'wheat variety response to seed cleaning and treatment after fusarium head blight infection', agrosystems, geosciences & environment, 2(1), : 1-8 Rasul, G. A. M. 2016. 'Effect of phosphorus fertilizer application on some yield components of wheat and phosphorus use efficiency in calcareous soil', journal of dynamics in agricultural research, 3(4): 46-51 Rehim, A., Farooq, M., Ahmad, F. and Hussain, M. 2012. 'Band placement of phosphorus improves the phosphorus use efficiency and wheat productivity under different irrigation regimes', international journal of agriculture and biology, 14(5). Richardson, A. E., J. P., Lynch, P. R. Ryan, , Delhaize, E., Smith, F. A., Smith, S. E., P. R., Harvey, M. H.Ryan, , E. J. Veneklaas, and H. Lambers, 2011. 'Plant and microbial strategies to improve the phosphorus efficiency of agriculture', plant and soil, 349(1) : 121-156 Roberts, H. 1981. 'Seed banks in soils', Advances in applied biology, 6, : 1-55 Shen, J., Yuan, L., Zhang, J., Li, H., Bai, Z., Chen, X., Zhang, W. and Zhang, F. 2011. 'Phosphorus dynamics: from soil to plant', Plant Physiology, 156(3): 997-1005 Tawaha, A., M.Turk, and G. Maghaireh, 2002. 'Response of barley to herbicide versus mechanical weed control under semi‐arid conditions', Journal of Agronomy and Crop Science, 188(2), : 106-112 Tessema, T., D. Tanner, and M. Hasenna, (1996) 'Grass weed competition with bread wheat in Ethiopia. 2: Prediction of grain yield loss and implications for economic weed control' Thomas, G. W. 1996. 'Soil pH and soil acidity', Methods of soil analysis. Part, 3(875), : 475-490 Thompson, K. and J. P. Grime, 1979.'Seasonal variation in the seed banks of herbaceous species in ten contrasting habitats', The Journal of Ecology, : 893-921 Tibola, C. S., J. M. C. Fernandes, and E. M. Guarienti, 2016. 'Effect of cleaning, sorting and milling processes in wheat mycotoxin content', Food Control, 60, : 174-179 Walker, R. H. 1995. 'Preventive weed management', Handbook of weed management systems, : 35-50
The two volumes of this handbook provide a comprehensive account of the emerging and vibrant science of the ecological restoration of both habitats and species. Ecological restoration aims to achieve complete structural and functional, self-maintaining biological integrity following disturbance. In practice, any theoretical model is modified by a number of economic, social and ecological constraints. Consequently, material that might be considered as rehabilitation, enhancement, re-construction or re-creation is also included. Principles of Restoration defines the underlying principles of restoration ecology, in relation to manipulations and management of the biological, geophysical and chemical framework. The accompanying volume, Restoration in Practice, provides details of state-of-the-art restoration practice in a range of biomes within terrestrial and aquatic ecosystems. The Handbook of Ecological Restoration will be an invaluable resource to anyone concerned with the restoration, rehabilitation, enhancement or creation of habitats in aquatic or terrestrial systems, throughout the world.
The two volumes of this handbook provide a comprehensive account of the emerging and vibrant science of the ecological restoration of both habitats and species. Ecological restoration aims to achieve complete structural and functional, self-maintaining biological integrity following disturbance. In practice, any theoretical model is modified by a number of economic, social and ecological constraints. Consequently, material that might be considered as rehabilitation, enhancement, re-construction or re-creation is also included. Principles of Restoration defines the underlying principles of restoration ecology, in relation to manipulations and management of the biological, geophysical and chemical framework. The accompanying volume, Restoration in Practice, provides details of state-of-the-art restoration practice in a range of biomes within terrestrial and aquatic ecosystems. The Handbook of Ecological Restoration will be an invaluable resource to anyone concerned with the restoration, rehabilitation, enhancement or creation of habitats in aquatic or terrestrial systems, throughout the world.
Grassland degradation can alter the structure and function of ecosystem and soil seed bank. Therefore, estimating the role of soil seed bank in vegetation regeneration of degraded grasslands is crucial. We selected grasslands with three levels of degradation, namely non-degraded (ND), mildly degraded (MD), and heavily degraded (HD) to analyze the effect of grassland degradation on soil seed bank, as well as the role of soil seed bank on vegetation regeneration of the alpine grasslands, China. Soil samples from each level were collected in May, before seedling emergence, in August, after completion of transient seed bank germination, and in December, after seed dispersal, to determine the seed density and species composition through germination experiment. Result showed that a total of 35 plant species was identified, including 15 species observed in both soil seed bank and above-ground vegetation. A total of 19, 15, and 14 species of soil seed bank were identified in December, May, and August, respectively. The most abundant species in soil seed bank were Compositae (5 species), followed by Poaceae (4 species), and Cyperaceae (3 species). Degradation level has no significant impact on species richness and Shannon-Wiener index of soil seed bank. In addition, sampling month and grassland degradation affected soil seed bank density, in which December>May>August, and ND>MD>HD, indicating that density of transient seed bank was greater than persistent seed bank. Soil seed bank density of surface layer (0–5 cm) accounting for 42%–72% of the total density, which was significantly higher than that of deep layer (5–10 cm). Similarity of species composition between vegetation and soil seed bank was low, and it increased with degradation level (ranged from 0.14 to 0.69). We concluded that grassland degradation affects soil seed bank density more than species diversity, and soil seed bank contributed slightly to vegetation regeneration of degraded alpine grassland. Therefore, it is unlikely that degraded alpine meadow can be restored solely through soil seed bank.
One of the most critical phases in the life cycle of plants encompasses early stages, since success in seed dormancy overcoming and germination as well as in seedling establishment represents a key process filtering the participation of species in plant communities. In this study, the requirements for dormancy breaking and germination of seeds of Helleborus foetidus were analyzed. The seeds were dormant with underdeveloped embryos (0.54 mm) at the time of dispersal and radicle emergence did not occur until embryos reached full size (3.6 mm). The light–temperature requirements for embryo growth and radicle emergence were studied correlating experiments under near-natural conditions with others under laboratory-controlled conditions. The embryos completed their growth and the radicle emerged when seeds were warm → cool stratified in darkness under a thermal sequence meeting late summer to early autumn temperature conditions. Conversely, cold stratified seeds did not germinate at winter temperatures (5 °C). The highest seed germination response (i.e., 75%) occurred in 6-month-old seeds incubated at 15/4 °C in darkness after being warm + cool stratified for 3 months (i.e., 32/18 °C for 1 month + 28/14 °C for 1 month + 25/10 °C for 1 month). In outdoor conditions, the embryo grew during late summer–autumn and the radicle emerged in late autumn, but the shoot did not emerge immediately because it was physiologically dormant too, so it required cold winter temperatures for dormancy breaking. Seedling establishment commenced at late winter–early spring, which is a more suitable season for seedling survival. In conclusion, the seeds of Helleborus foetidus exhibit deep simple epicotyl morphophysiological dormancy (MPD), which is ecologically well adapted to temperate forest regions. This is the second report of this level of MPD in Ranunculaceae.
A Soproni-hegyvidék területén végzett talaj magbank vizsgálat és a mintavételi helyek cönológiai felvételezése a hazai flóra 120 fajának magbank típus szerinti besorolását tette lehetővé. E fajok magbank típusát a Magbank adatbázis (CSONTOS 2001a) részben tartalmazza, 45 faj esetén azonban a vizsgálat új adatokkal szolgál. Az adatbázisból ismert és az újonnan meghatározott magbank típusok 56%-a megegyezik. Az eltérően besorolt fajok tekintetében a vizsgálat mindössze hat fajnál utal a magvak hosszabb életképességére, a többi faj magtúlélését az adatbázishoz képest alábecsülte, részben az üvegházi hajtatásos módszernek köszönhetően. Az adatbázisból eddig nem ismert fajok közül 23 esetében a magbank típus nagy biztonsággal megállapítható. A többi faj magbank típusára a túl kevés vagy ellentmondásos adat miatt csak következtethetünk, azonban további vizsgálatokkal kiegészítve ezek az adatok is hozzájárulhatnak a fajok magbank típusokba történő precíz besorolásához.
The two volumes of this handbook provide a comprehensive account of the emerging and vibrant science of the ecological restoration of both habitats and species. Ecological restoration aims to achieve complete structural and functional, self-maintaining biological integrity following disturbance. In practice, any theoretical model is modified by a number of economic, social and ecological constraints. Consequently, material that might be considered as rehabilitation, enhancement, re-construction or re-creation is also included. Principles of Restoration defines the underlying principles of restoration ecology, in relation to manipulations and management of the biological, geophysical and chemical framework. The accompanying volume, Restoration in Practice, provides details of state-of-the-art restoration practice in a range of biomes within terrestrial and aquatic ecosystems. The Handbook of Ecological Restoration will be an invaluable resource to anyone concerned with the restoration, rehabilitation, enhancement or creation of habitats in aquatic or terrestrial systems, throughout the world.
Plant invasions in tropical ecosystems are being increasingly realized particularly in highly dynamic but fragile dry tropical ecosystems, where there is generally little ecological information on invasions in subterranean vegetation. The present study was carried out to understand the floristic composition of both seed bank and standing vegetation across a range of five diverse anthropo-ecosystems in an urban region in Indian dry tropics. A total of one hundred soil samples (each of size of 25cm×25cm from 0-5 cm and 5-10 cm depth) from five anthropic sites (vegetation of University campus, polluted Kali River bank, Brick kiln, Waste land and Road side) were analyzed for their taxonomic position, life form and bio-geographic origin of the seedling emergents in relation to the flora in standing vegetation. A total of 221 plant species (58% aliens, 34% of aliens of American origin, 75% weedy herbs) in standing vegetation spread over 54 families were recorded in standing vegetation of the study sites with more than 55% representation from eight dominant families led by Fabaceae, Poaceae and Asteraceae followed by Malvaceae, Amaranthaceae and Solanaceae. In contrast, a total of 81 seed bank flora (10 unidentified, 62% aliens, 43% of American origin, 87% herbs) distributed over 32 angiospermic families were recorded. While none of the seed bank vegetation at any site showed significant similarity with its standing vegetation indicating the minor role of seed bank flora in the regeneration of the standing plant communities above ground. However, a considerable similarity among seed banks and standing vegetation at other sites indicated a significant possible role of anthropogenic activities in the urban regions of Indian dry tropics, evinced by the largest proportion of grasses and herbs dominated by exotics, especially of American origin. These aliens through successful naturalization via seed banks may cause homogenization of floristic structure. In conclusion, the present study revealed a heavy scale of intrusion by the alien plants dominated by American elements into not only standing vegetation but also in seed banks across the anthropic sites in urban regions in Indian dry tropics which is likely to alter the standing vegetation floristic structure with a larger abundance of alien flora.
Jelen dolgozatunkban négy erdei lágyszárú, Simon természetvédehni-érték besorolása szerint zavarástűrő faj: a Cardamine impatiens L., a Geum urbanum L., a Rumex sanguineus L. és a Verbascum austriacum Schott talajmagbankjának tulajdonságairól számolunk be. Az említett fajok magtúlélési képességét eltemetéses kísérletben vizsgáltuk. Frissen gyűjtött magvaikat sterilizált homokkal elkeverve, majd agyagcserepekbe töltve 0,65 m mélyen eltemettük, tíz ismétlésben, esetenként 100-100 magot felhasználva. Fajonként 1-1 százmagos tételt ástunk elő az eltemetést követő 1., 2., 3., 4., 6. és 19. évben, majd azokat üvegházi körülmények között csíráztattuk. A C. impatiens magbankja rövid távú perzisztensnek bizonyult. Ennél a fajnál ez feltehetőleg két ellentétes hatás eredőjeként jött létre, mivel az erdei környezet inkább a tranziens magbank típusnak, ugyanakkor a faj kétéves életformája és a bolygatottabb élőhelyeken való előfordulása viszont inkább a hosszú távú perzisztens magbank típusnak kedvezne. A G. urbanum esetében hosszú távú perzisztens magbankot igazoltunk, ami az első ilyen közlés a fajra vonatkozóan. Megjegyzendő, hogy a lapos és megnyúlt magvú fajok esetében az ilyen magbank típus viszonylag ritka, tehát a G. urbanum kivételes viselkedésűnek mondható. A V. austriacum magbankja, más, korábban vizsgált ökörfarkkóró fajokéhoz hasonlóan kitűnő magtúlélő képességet mutatott, a 19. évben is gyakorlatilag az első évivel megegyező arányban csírázott. A R. sanguineus esetében a szakirodalomban mindhárom fő magbank típusra nézve találunk közléseket. Eredményeink szerint ez a faj egyértelműen képes fenntartani hosszú távú perzisztens magbankot a talajban. Magvai 19 év elteltével is 43 százalékban csíráztak. Dolgozatunkban mérlegeljük még az eltemetéses magbank vizsgálatok használhatóságát a fajok magbank típusának feltárása szempontjából.
Seeds of Polygonum aviculare placed in soil in pots in the field exhibit cyclic changes in dormancy. Innate dormancy in fresh seeds is overcome during autumn and winter and is minimal when seedlings emerge in the field from late February onwards. In late May, when seedlings cease to emerge, dormancy is induced once more in the remaining viable seeds and is not overcome until the following winter. This cycle was found in seeds held at different depths below the soil surface and could be simulated in the laboratory by exposing seeds to periods of low (4⚬ C) and high (23-25⚬ C) temperature under conditions of enforced dormancy. The extent of germination is also influenced by the presence of the pericarp. Soil disturbance in spring increases percentage emergence but does not extend the emergence period; disturbance at other times has no effect.
At Litton Mills, on the Carboniferous limestone in Derbyshire, a field experiment was carried out in order to investigate the mechanisms preventing the incursion of Arrhenatherum elatius into an area of derelict calcareous grassland dominated by Festuca ovina. The results of the investigation suggest that Arrhenatherum elatius is vulnerable to desiccation under conditions in which seedling growth and, in particular, root penetration is limited by a deficiency of phosphorus and nitrogen. The success of Festuca ovina at the site appears to be related to the ability of the species to tolerate moisture stress under conditions in which its growth is severely restricted by mineral nutrient stress. It is suggested that interactions between mineral nutrient stress and desiccation may be involved in the control of variation between different kinds of calcareous grassland in Britain, in the effects of aspect upon plant distribution, and in the maintenance of the refugia of certain rare calcicolous species.
It is shown that Hordeum murinum requires at least a fertile soil of moderately high pH, low competition and high light intensity for maximum performance. As no single one of these conditions is peculiar to the ruderal environment it is concluded that it is probably the requirement for this unusual combination which accounts for the restriction.
(1) The dynamics of seed populations of Vulpia fasciculata were investigated on two dune systems in North Wales. Loss of seed viability, seed predation by invertebrates and the failure of seedlings to establish due to wind-drag were the major factors involved in the loss of individuals between seed dissemination and seedling establishment. (2) The use of radioactive tracers provided a particularly effective method for following the fate of individuals during the seed and early seedling stages of the life cycle. (3) A small proportion of the fresh seeds was innately dormant, but after a short period of after-ripening most of these seeds had lost their innate dormancy and were capable of germination. More than 99· 5% of the seeds germinated in the year of their production. (4) The germination strategy of V. fasciculata is compared with those of other annuals, and the significance of different dormancy and germination strategies in different environments is discussed.
Flowering, seed production and the dynamics of the buried seed flora were studied in populations of Ranunculus bulbosus, R. acris and R. repens. Flowering and seed set of all three species was much less predictable from year to year than the vegetative reproduction of R. repens. R. bulbosus which depends wholly and R. acris which depends largely on seed production for multiplication produced 6-10 times as many seeds as R. repens (both per plant and per unit area). The maximum number of daughter ramets produced by a plant of R. repens in a season was 16, but half of the parents produced only 1 ramet. In denser populations there was evidence of density-dependent regulation in (a) a higher mortality of vegetative parents, and (b) a lower probability of a plant producing a ramet; the number of ramets per plant did not show significant correlation with density. In none of the species did flowering appear to increase the mortality risk and plants of R. bulbosus and R. acris that flowered had a greater probability of survival than those that did not. Seed was lost from the populations by predation of flowers and infructescences, and by predation by small mammals of seed on the ground after shedding. The remainder was classified in repeated samples into the categories: (a) germinated; (b) enforced dormant; (c) induced dormant; and (d) dead. A high proportion of the seed of R. bulbosus and R. acris germinated during the study period and there was rapid loss of viability in the remainder (half life of the seed populations--R. bulbosus, 8 months; R. acris, 5 months). In marked contrast, few seeds of R. repens germinated and the decay rate of the remainder was too slow to detect significantly. R. repens, with dependable vegetative reproduction, weak flowering and seed production but great seed longevity, contrasts strikingly with the other species with little or no vegetative reproduction, high seed output, rapid germination and a short life of the buried seed.
Grassland vegetation in the Sheffield region has been classified by information analysis using frequency data. On the basis of 630 samples, more than fifty types of limestone, neutral and acidic grasslands are described and an indication is given of the range in environmental features associated with each type. Principal components analysis has been used to confirm and interpret the results of the classification. The major causes of variation in the grasslands are associated with the distribution of geological formations, with soil pH and with altitude. Magnesian Limestone grasslands, with Brachypodium pinnatum or Zerna erecta, are distinct from Carboniferous Limestone grasslands characterized by Arrhenatherum elatius or Festuca ovina. F. ovina-Agrostis tenuis grasslands are widespread on mildly acidic soils and Deschampsia flexuosa is ubiquitous on strongly acidic soils. Vaccinium myrtillus links acidic grassland with moorland vegetation. Examination of the data suggests that there is continuous variation in much of the vegetation, but this does not preclude the occurrence of discrete plant associations nor invalidate the classification. Limestone grassland is strongly influenced by local factors, whereas acidic grassland appears more uniform on a regional basis. A procedure using simple floristic and environmental attributes is put forward as a possible aid to the rapid recognition and better understanding of the classified grassland types.
(1) Variation in standing crop and in litter has been measured by seasonal sampling and sorting of the herbaceous vegetation at thirteen sites in the Sheffield region. The vegetation types examined comprised tall herb, woodland floor and grassland communities. At each site the living fraction in 4-10 replicated 0.25 m2 quadrats was separated into its components, and graphs were plotted showing the shoot phenology of the more common species. (2) At the sites in which herbaceous vegetation was growing under fertile, relatively undisturbed conditions, there was a large peak in standing crop during the summer ($> 400 g m^{-2}$ dry weight), and the vegetation contained few species. The low species-densities at these sites appeared to be related to the ability of certain species to exercise competitive dominance, a phenomenon involving the rapid expansion of a dense leaf canopy during the period June-August, coupled with the production of a high density of persistent litter. (3) In the woodland and grassland sites examined, the sum of the maximum standing crop and the litter did not exceed 800 g m-2, and a variety of plant phenologies was encountered. At two of the woodland sites vernal species were prominent; these plants exhibited truncated periods of shoot growth, which preceded full expansion of the tree canopy and followed immediately the marked decline in density of tree litter in early spring. (4) At the sites where the standing crop was severely restricted by low soil fertility, the commonest phenological pattern was that of the evergreen; in certain of these species, no seasonal peak of shoot expansion could be detected. In two of the limestone grasslands investigated, forbs with mid-summer peaks of shoot expansion were prominent; the majority of these plants had relatively deep root-systems, and appeared to exploit reserves of moisture during periods when many grasses were subjected to desiccation. (5) A consistent feature of the results was the marked amplitude of seasonal variation in the abundance of bryophytes, expansion of which coincided with the moist, cool conditions of spring and autumn. (6) A general conclusion drawn from this study relates to the control of species-density in herbaceous vegetation. The results suggest that the potential for high species-density corresponds approximately to the range of 350-750 g m-2 in the sum of maximum standing crop and litter.
A complete description of a plant community must include the buried viable seeds in the soil. The plants occurring in this form are a part of the flora, which helps to determine the community, even though they are not readily evident. The importance of defining an ecosystem's flora is reviewed. When the soil's buried viable seed population is used to help determine the flora, various problems arise since perennial plants reproduce much less abundantly by seed than do annuals, laboratory germination conditions probably do not suit all species, and seeds are not distributed at random so sampling is made difficult. In an investigation of buried viable seeds in two grazed and ungrazed California bunchgrass sites poor correspondence between vegetation and soil seed populations was found. Numbers were 8000 to 12,000 seeds per m2. Figures of this order or magnitude are general in the periodical literature which describes the buried viable seed populations and the factors which influence them qualitatively and quantitatively in various kinds of arable, mesic pastured or mown, steppe, and forest plant communities.
Not only are the plants evident above ground in a stand of vegetation part of the ecosystem which includes that vegetation, so also are the plant disseminules in the soil.
This paper records a determination of the kinds and numbers of viable seeds in two stands ofStipa pulchra, bunchgrass vegetation in the eastern foothills of the central Coast Ranges of California. Such vegetation is variable from year to year, over a climatic cycle of years, and successionally (i.e.), it is seral and therefore changes with time, other habitat factors being constant (Heady 1958). By no means all the species which can occur in this vegetation over a period of several years are evident above ground at one time. We have attempted to use the soil content of buried, viable seeds in the two stands as a measure of this potential flora.
An experiment in which Hordeum murinum was grown at a control site and at two sites with adverse climates showed that failure of the species in adverse climates is due to a combination of effects on growth, development, fruit production, ripening and dispersal, and seedling establishment. It is concluded that the previously observed correlations between the distribution of the species and temperature and rainfall are direct, and not simply due to the pattern of distribution of ruderal habitats. Predisposition of the species for urban habitats in cooler and wetter areas is probably due to the occurrence of warmer, drier micro-habitats.
IT is well known that the upper layers of many types of soil contain large populations of buried, dormant seeds estimated to amount to many thousands per acre in some instances1. Many of these buried seeds are viable and germinate readily when the soil is cultivated or disturbed in other ways. There is good evidence that such seeds can remain dormant in the soil for long periods; indeed, evidence has recently been presented that seeds which have lain in the soil for as much as 1,700 years are still viable2.
In a 6‐year experiment with a naturally occurring population of viable weed seeds, the numbers in the top 9 in. of soil decreased exponentially from year to year in the absence of further seeding. The rates of loss were equivalent to 22% per year in undisturbed soil, 30% per year on plots dug twice a year (March and September) and 36% per year on those dug four times a year (March, June, September, December). Seed numbers of individual species also decreased exponentially, although not all at the same rates.
On the dug plots, the numbers of seedlings that emerged each year decreased exponentially once the regimes had become established. The proportions of the viable seeds which gave rise to seedlings in the course of a year were 7 % on plots dug twice and 9 % on those dug four times a year; although there was some variation, these proportions remained much the same from year to year. On undisturbed soil the number of seedlings that emerged declined rapidly, and in the 4th year represented no more than 03% of the viable seeds still present in the top 9 in. of soil.
Studies of germination response to temperature and measurements of meteorological conditions in the field were made with populations of Hyacinthoides non-scripta growing in two places in south-eastern England.
Seeds did not germinate when sown directly at temperatures over the range 6° to 31 °C. Germination occurred in response to a two phase treatment (a) a high temperature conditioning phase with an optimum at 26° to 31 °C; (b) a germination phase at 11 °C. No response was found to a low temperature conditioning phase equivalent to winter chilling.
Soil temperature measurements during late summer and autumn showed that these were generally below the optimum for the conditioning phase, but nevertheless within the range at which changes leading to germination did occur. The results suggested that germination occurs naturally as temperatures fall to c. 11 °C in late autumn and that seedlings overwinter and grow whenever periods of mild weather permit. (Young seedlings were identified in the field in late November.) A residue of ungerminated seed may overwinter as an insurance against loss of overwintering seedlings. The proportion of dormant seed to germinated seedlings appears to be critically dependent on temperature and may vary from year to year, site to site or position within a site.
An examination of meteorological data suggested that the natural distribution of the species is defined by the mean daily minimum temperature of the coldest winter month (> 0 °C) and the mean daily maximum temperature of the warmest summer month (< 25 °C). The germination responses identified appear to provide a finely balanced mechanism which affords maximum insurance on established sites and maximum opportunism in the colonization of new sites.
According to ‘Gause's hypothesis’ a corollary of the process of evolution by natural selection is that in a community at equilibrium every species must occupy a different niche. Many botanists have found this idea improbable because they have ignored the processes of regeneration in plant communities.
Most plant communities are longer‐lived than their constituent individual plants. When an individual dies, it may or may not be replaced by an individual of the same species. It is this replacement stage which is all‐important to the argument presented.
Several mechanisms not involving regeneration also contribute to the maintenance of species‐richness:
differences in life‐form coupled with the inability of larger plants to exhaust or cut off all resources, also the development of dependence‐relationships,
differences in phenology coupled with tolerance of suppression,
fluctuations in the environment coupled with relatively small differences in competitive ability between many species,
the ability of certain species‐pairs to form stable mixtures because of a balance of intraspecific competition against interspecific competition,
the production of substances more toxic to the producer‐species than to the other species,
differences in the primary limiting mineral nutrients or pore‐sizes in the soil for neighbouring plants of different soecies, and
differences in the competitive abilities of species dependent on their physiological age coupled with the uneven‐age structure of many populations.
The mechanisms listed above do not go far to explain the indefinite persistence in mixture of the many species in the most species‐rich communities known.
In contrast there seem to be almost limitless possibilities for differences between species in their requirements for regeneration, i.e. the replacement of the individual plants of one generation by those of the next. This idea is illustrated for tree species and it is emphasized that foresters were the first by a wide margin to appreciate its importance.
The processes involved in the successful invasion of a gap by a given plant species and some characters of the gap that may be important are summarized in Table 2.
The definition of a plant's niche requires recognition of four components:
the habitat niche,
the life‐form niche,
the phenological niche, and
the regeneration niche.
A brief account is given of the patterns of regeneration in different kinds of plant community to provide a background for studies of differentiation in the regeneration niche.
All stages in the regeneration‐cycle are potentially important and examples of differentiation between species are given for each of the following stages:
Production of viable seed (including the sub‐stages of flowering, pollination and seed‐set),
dispersal, in space and time,
germination,
establishment, and
further development of the immature plant.
In the concluding discussion emphasis is placed on the following themes:
the kinds of work needed in future to prove or disprove that differentiation in the regeneration niche is the major explanation of the maintenance of species‐richness in plant communities,
the relation of the present thesis to published ideas on the origin of phenological spread,
the relevance of the present thesis to the discussion on the presence of continua in vegetation,
the co‐incidence of the present thesis and the emerging ideas of evolutionists about differentiation of angiosperm taxa, and
the importance of regeneration‐studies for conservation.
Diurnal fluctuations in temperature may initiate or accelerate germination in certain flowering plants, and the effectiveness of the stimulus varies according to the amplitude of fluctuation and the presence or absence of light. Attempts to assess the adaptive significance of the phenomenon, however, have been limited by the scarcity of data for species of contrasted ecology. We report here an investigation of germination responses to fluctuating temperatures, conducted on seeds of herbaceous species collected from native populations near Sheffield. The results suggest that requirements for diurnal fluctuations in temperature are characteristic of the germination of species from particular types of habitat and provide mechanisms which cause seeds to germinate at times and in places favourable for seedling establishment.
The Identification of Weed Seedlings of Farm and Garden On the viable seeds present in the soil beneath pastures
- R J G Chancellor
- W E J Milton
Chancellor, R. J. (1966). The Identification of Weed Seedlings of Farm and Garden. Blackwell Scientific Publications, Oxford. Chippindale, H. G. & Milton, W. E. J. (1934). On the viable seeds present in the soil beneath pastures. Journal of Ecology, 22, 508-531.
Interpretation of small-scale patterns in the distribution of plant species in space and time. Structure and Functioning of Plant Populations
- J P Grime
Grime, J. P. (1977). Interpretation of small-scale patterns in the distribution of plant species in space and time. Structure and Functioning of Plant Populations (Ed. by J. W. Woldendorp), pp. 101-124.
Shade avoidance and shade tolerance in flowering plants. II. Effects of light on the germination of species of contrasted ecology. Light as an Ecological Factor A comparative study of germination characteristics in a local flora
- J P Grime
- B C V Jarvis
- A M Neal
- J Rodman
- S Shaw
Grime, J. P. & Jarvis, B. C. (1975). Shade avoidance and shade tolerance in flowering plants. II. Effects of light on the germination of species of contrasted ecology. Light as an Ecological Factor (Ed. by R. Bainbridge, G. C. Evans & 0. Rackham), pp. 525-532. Blackwell Scientific Publications, Oxford. Grime, J. P., Mason, G., Curtis, A. V., Neal, A. M., Rodman, J. & Shaw, S. (1980). A comparative study of germination characteristics in a local flora. New Phytologist, 77.
An investigation of the effect of temperature upon the germination and growth of native species, using temperature-gradient techniques
- G Mason
Mason, G. (1976). An investigation of the effect of temperature upon the germination and growth of native species, using temperature-gradient techniques. Ph.D. thesis, University of Sheffield.
Studies of germination and establishment of selected species with special reference to the fate of seeds
- A M Mortimer
Mortimer, A. M. (1974). Studies of germination and establishment of selected species with special reference to the fate of seeds. Ph.D. thesis, University College of North Wales.
An ecological investigation of germination responses to diurnal fluctuations in temperature
- K Thompson
Thompson, K. (1977). An ecological investigation of germination responses to diurnal fluctuations in temperature. Ph.D. thesis, University of Sheffield.