Buried Seeds Research Articles

Book Review: Alexia Salvatierra and Brandon Wrencher, Buried Seeds: Learning from the Vibrant Resilience of Marginalized Christian Communities

Book Review: Alexia Salvatierra and Brandon Wrencher, <i>Buried Seeds: Learning from the Vibrant Resilience of Marginalized Christian Communities</i>

Post-fire clumping of seedlings of Cape Proteaceae species: ecological, evolutionary and conservation implications

Background Spatial clumping of plants results in intense competition. Aims We analysed the extent of clumping of Proteaceae seedlings across the Cape Floristic Region after fire. Methods To demonstrate the extent of clumping in 23 species, we analysed the seedling and adult densities in 290 post-fire surveys each of 100 × 1 m2 plots using standard indices of clumping. Key results We detected clumping of Cape Proteaceae seedlings, whereas parent plants were less clumped. The clumping is not due to limited safe sites for seedlings because the number of plots at a site with at least one seedling was positively related to the number of seedlings at the site. Sites with seedlings were enriched in nutrients relative to those without. Conclusions The possible benefits of clumping are saturation of granivores and co-location of buried seeds with nutrient-rich patches of fire-derived ash and debris. A cause of clumping is seeds sticking together. Clumping, which is strongly intraspecific, has implications for trait evolution and the dominance of reseeders over resprouters. Strong clumping reduces the usefulness of the widely used seedling:parent index to determine whether fires were favourable or not. Implications Clumping has implications for understanding seed dispersal distances, seedling versus adult traits, fire responses and demography.

Book Review: Alexia Salvatierra and Brandon Wrencher, Buried Seeds: Learning from the Vibrant Resilience of Marginalized Christian Communities

Book Review: Alexia Salvatierra and Brandon Wrencher, <i>Buried Seeds: Learning from the Vibrant Resilience of Marginalized Christian Communities</i>

Characterisation and dynamics of the fungal communities of Avena fatua and Echinochloa crus‐galli seeds in soil seed bank

AbstractSurvival in the soil seed bank is critical to a weed maintaining populations in arable lands. The role of the seed‐borne fungi in seed decay or survival needs to be determined to find solutions for reducing the weed seed banks in environmentally friendly ways. In this study, changes of the fungal microbiome after seed burial were determined in two economically important weed species, wild oat and barnyard grass. Seeds collected in different populations were buried in two sites and exhumed at intervals over the period of 1.5 years to test the seed fate. Epiphytic and endophytic fungal microbiota of seeds was characterised using both culture‐based approach and NGS of ITS1 region. The proportion of visually intact seeds and decayed seeds was different between the two burial sites. The observed species richness of the isolated epiphytic fungi was higher in the fresh compared to the buried seeds. Fungal taxa determined by NGS amplicon sequencing only partly coincided with the isolated fungi, revealing higher diversity in buried seeds. The dynamic of taxonomic structure of the fungal community was less pronounced in wild oat seeds compared to the barnyard grass seeds, where both endophytic and epiphytic communities were significantly different in the buried seeds and differed between the burial sites. It can be concluded that the epiphytic fungal communities change after seed burial in both plant species, while endophytic communities are more stable in the intact seeds and changes of the fungal community in the seed endosphere may be associated with seed decay.

Characterization of tadpole shrimp, Triops longicaudatus (Notostraca: Triopsidae), injury to rice and its effect on rice seedling establishment.

Rice seedlings of different stages of development were infested with tadpole shrimp (TPS, Triops longicaudatus [LeConte]), of different sizes in four experiments conducted in a lath house in Colusa, CA, during 2015 and 2016. Tadpole shrimp size was based on carapace length. Rice seedling stages were classified as S0 if no structures were present; S1 if only the coleoptile was present; S2 if the coleoptile and radicle were present; S3-I if the prophyll had emerged; S3-II if the first true leave had emerged but was not unfurled; and V1 if the first true leave was unfurled. Results showed that TPS of all sizes are capable of injuring rice and reducing seedling establishment, with larger TPS causing more seedling establishment reduction than medium or small TPS. The coleoptile, radicle, and roots were the structures most injured by TPS. During the S0 stage, TPS buried seeds, preventing their establishment. Seedling stages S1, S2, and S3-I were found to have the highest risk of injury by TPS, while seedling stage V1 had the lowest. Pearson's correlation between injured seedlings and the normalized number of established seedlings indicates that injury to the coleoptile, root, and radicle combined are the most important in preventing seedling establishment.

Environmental and seed-position effects on viability and germination of buried seeds of an invasive diaspore-heteromorphic annual grass.

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.

Differences in germination traits of time-separated seed collections of dry forest species from Central Zambia and the potential role of climate

Abstract Time-separated seed collections with a separation period of 12–18 years were used to study recent changes in germination traits and the role of climate factors in seven tropical dry forest (TDF) woody species in Zambia, southern Africa. In all the species, peak and final germination were lower in recent (2016–2021) seed collections than in historic (1998–2005) seed collections during the first germination season. However, in species with seed dormancy, both peak and final germination after one year burial were higher in recent seed collections than in historic seed collections. Three monthly climate factors had significant effects on final germination in the different species and the timing of most of these factors was during seed development and ripening that suggest that these factors operated through mother plants. In species with seed dormancy, post-first-year germination of buried seeds responded to climate factors in the regeneration niche. Climate factors that significantly affected germination included those that changed over the separation period between historic and recent seed collections. This indicates that short-time climatic changes may have the potential to impact germination in TDF woody species of southern Africa. The germination responses to climate factors were both positive and negative and it is not clear whether these are adaptations or not. Further research is required to assess the adaptive significance of these changes in germination traits in TDF species of southern Africa.

Plant Production Protocols from Seeds of Threatened Atropa baetica and Widespread A. belladonna, Both Rich in Alkaloids.

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.

Drought Stress Affects the Reproductive Biology of Avena sterilis ssp. ludoviciana

Avena sterilis ssp. ludoviciana (hereafter, A. ludoviciana) is considered the most difficult-to-control winter weed in the Northern Grains Region (NGR) of Australia. The abundance of this weed has increased after the adoption of the no-tillage conservation agriculture (NTCA) approach, which does not bury seeds deep in the soil profile. In addition, the increasing frequency and intensity of drought stress events during the late winter to early spring period in the NGR may modify this weed’s persistence mechanisms, which may further impact crop production. The present study focused on plant maturity time and seed production, dormancy, and longevity of four NGR A. ludoviciana biotypes in relation to the severity of drought stress over 2 consecutive years. Plants of all four A. ludoviciana biotypes were grown under 100% plant available water capacity (PAWC) until panicle initiation. At panicle initiation, very mild (80% PAWC), mild (60% PAWC), moderate (40% PAWC), and severe (20% PAWC) drought stresses were imposed on plants and continued through to maturity; an additional subset of plants were maintained at 100% PAWC through to maturity (control). Plants exposed to severe drought stress matured 24 days earlier than control plants, and produced 34% fewer filled seeds, with seeds having a 42% lower mass, 70% less dormancy, and shorter predicted longevity of at least 2 years compared to the seeds produced on control plants. All reproductive traits were less affected when the severity of the drought stress was decreased. The increasing frequency of drought stress in combination with the widely adopted practice of NTCA favours seeds of A. ludoviciana to undergo rapid germination in the following autumn/winter NGR planting season. However, effective control of A. ludoviciana remains a challenge in the NGR due to this weed’s genetic variability with respect to its response toward the seasonal variability of the NGR.

Olfactory misinformation reduces wheat seed loss caused by rodent pests

Alternatives to pesticides are urgently needed to meet sustainable agriculture goals but few options are available for many systems. Here we test how a form of olfactory misinformation on a newly sown wheat crop can prevent wild house mice (Mus musculus) from finding buried seeds. Our misinformation tactic, odour camouflage, reduced seed loss by >63%, providing a simple, non-lethal and ethical way to reduce seed damage and avoid rodenticide use.

The morphological and ecological variation of Arctostaphylos (Ericaceae) fruit: A link between plant ecology and animal foraging behavior.

Persistent soil seed banks are characteristic of Arctostaphylos (Ericaceae) species in the Mediterranean-climate California Floristic Province. While most species are obligate seeders, regeneration of stands of all Arctostaphylos species ultimately depends on post-fire seedling recruitment. Arctostaphylos seed banks are created, in large part, by scatter-hoarding rodents. Variation in fruit morphology, therefore, is expected to impact the Arctostaphylos-rodent interaction. Seeds produce sufficient rewards (nutritious mature embryo) to entice rodents to disperse and ultimately bury seeds in the soil. Hard seed coats increase the time required to extract the embryo, encouraging rodents to choose storage over immediate predation, and nutlets are frequently empty. We assessed the variation of fruit nutlet fusion and seed viability among 38 Arctostaphylos taxa. Factors such as latitude, elevation, life history, ploidy, and phylogenetic position were also analyzed. Generalized mixed-effects models were used to determine the factors contributing to variation in fruit nutlet fusion and seed viability. Our results indicate that fruit volume and shape are the most important variables affecting nutlet fusion and seed viability. Additionally, other potential influences only show a weak correlation and are not predicted to significantly impact nutlet fusion or seed viability. These findings provide insights into evolved strategies used by plants to increase reproductive success via scatter-hoarding rodents. Our study benefits the conservation and restoration of Arctostaphylos stands by emphasizing the importance of animal-mediated dispersal and providing estimates of seed viability for different species. With the anticipated effects of climate change, such as departures from historic fire regimes, the preservation of the relationship between plants and animal foragers is crucial for the continued survival of Arctostaphylos and California's evergreen chaparral.

Elevated Temperature Affects Avena sterilis ssp. ludoviciana Reproductive Biology

The weed Avena sterilis ssp. ludoviciana has a high economic impact in the winter cereal crop production systems of Australia’s northern grains region (NGR). In the NGR, the frequency of high-temperature periods at the end of winter is increasing. This shift in climate may modify this weed’s maturity time and reproductive biology, and thereby impact on crop production. This study examined the reproductive biology of four A. ludoviciana biotypes in relation to elevated temperature when applied at different times during their seed development. Plants of all four A. ludoviciana biotypes were grown in an ambient temperature glasshouse (23/14 °C day/night). At panicle initiation, a portion of the plants were transferred to an elevated temperature glasshouse (29/23 °C day/night) and remained there until maturity. This process of plant movement was repeated on three further occasions with separate batches of plants, each 10 days apart. The remaining plants were kept under ambient conditions for their whole lifespan. Plants exposed to elevated temperature from panicle initiation to maturity, matured 18 days earlier than plants kept under ambient conditions, had 30% fewer filled seeds, 37% lower seed mass, and 40% less seed dormancy. Depending on the time and duration of plants exposed to elevated temperature, predicted seed longevity was ranged from 1 to 4 years in the soil seedbank. All reproductive traits were less affected when plants were exposed to elevated temperature at a later stage of development. If the frequency of high-temperature periods continues to increase, then it may lead to the development of less dormant populations of this weed that would be ready to germinate and re-infest the next winter crops under no-tillage conservation agriculture (that does not bury seeds deep in the soil profile). However, the seasonal climatic variability of the NGR in addition to the weed’s natural genetic variability may contribute to a seedbank of both dormant and less dormant seeds—making this species an even more difficult-to-control weed.

Patterns of Seedling Emergence from North Dakota Grazing Lands Invaded by Kentucky Bluegrass

Kentucky bluegrass (Poa pratensis, POPR) is a dominant invader of the northern Great Plains, but little is known about its impact on seedbanks. We quantified patterns of seedling emergence from samples of litter, thatch, and mineral soil collected from invaded grassland sites, hypothesizing that POPR would be the dominant emergent species, but that composition of seedling populations would differ between the layers with a higher incidence of native species in mineral soil. POPR accounted for 84% of the emergent seedlings, and curves, fit with a Hill model, indicated that 50% of cumulative emergence was reached after 40.5 d. Rank-abundance diagrams were highly skewed and strongly dominated by POPR but indicated differences among litter, thatch, and soil layers. POPR accounted for 94.3%, 71.9%, and 69.9% of emergent seedlings from litter, thatch, and soil layers, respectively. More POPR seedlings emerged from litter material than the other layers. Management of POPR by fire or grazing should consider their possible effects on seed production, distribution, and longevity of buried seeds.

A quantitative analysis of temperature-dependent seasonal dormancy cycling in buried Arabidopsis thaliana seeds can predict seedling emergence in a global warming scenario.

Understanding how the environment regulates seed-bank dormancy changes is essential for forecasting seedling emergence in actual and future climatic scenarios, and to interpret studies of dormancy mechanisms at physiological and molecular levels. Here, we used a population threshold modelling approach to analyse dormancy changes through variations in the thermal range permissive for germination in buried seeds of Arabidopsis thaliana Cvi, a winter annual ecotype. Results showed that changes in dormancy level were mainly associated with variations in the higher limit of the thermal range permissive for germination. Changes in this limit were positively related to soil temperature during dormancy release and induction, and could be predicted using thermal time. From this, we developed a temperature-driven simulation to predict the fraction of the seed bank able to germinate in a realistic global warming scenario that approximated seedling emergence timing. Simulations predicted, in accordance with seedling emergence observed in the field, an increase in the fraction of the seed bank able to emerge as a result of global warming. In addition, our results suggest that buried seeds perceive changes in the variability of the mean daily soil temperature as the signal to change between dormancy release and induction according to the seasons.

Vertical distribution of soil seed bank and the ecological importance of deeply buried seeds in alkaline grasslands.

BackgroundSoil seed banks play a central role in vegetation dynamics and may be an important source of ecological restoration. However, the vast majority of seed bank studies examined only the uppermost soil layers (0–10 cm); hence, our knowledge on the depth distribution of seed bank and the ecological significance of deeply buried seeds is limited. The aim of our study was to examine the fine-scale vertical distribution of soil seed bank to a depth of 80 cm, which is one of the largest studied depth gradients so far. Our model systems were alkaline grasslands in East-Hungary, characterised by harsh environmental conditions, due to Solonetz soil reference group with Vertic horizon. We asked the following questions: (1) How do the seedling density and species richness of soil seed bank change along a vertical gradient and to what depth can germinable seeds be detected? (2) What is the relationship between the depth distribution of the germinable seeds and the species traits?MethodsIn each of the five study sites, four soil cores (4 cm diameter) of 80 cm depth were collected with an auger for soil seed bank analysis. Each sample was divided into sixteen 5-cm segments by depth (320 segments in total). Samples were concentrated by washing over sieves and then germinated in an unheated greenhouse. Soil penetration resistance was measured in situ next to each core location (0–80 cm depth, 1-cm resolution). We tested the number and species richness of seedlings observed in the soil segments (N = 320), using negative binomial generalized linear regression models, in which sampling layer and penetration resistance were the predictor variables. We ran the models for morphological groups (graminoids/forbs), ecological groups (grassland species/weeds) and life-form categories (short-lived/perennial). We also tested whether seed shape index, seed mass, water requirement or salt tolerance of the species influence the vertical distribution of their seed bank.ResultsGerminable seed density and species richness in the seed bank decreased with increasing soil depth and penetration resistance. However, we detected nine germinable seeds of six species even in the deepest soil layer. Forbs, grassland species and short-lived species occurred in large abundance in deep layers, from where graminoids, weeds and perennial species were missing. Round-shaped seeds were more abundant in deeper soil layers compared to elongated ones, but seed mass and ecological indicator values did not influence the vertical seed bank distribution. Our research draws attention to the potential ecological importance of the deeply buried seeds that may be a source of recovery after severe disturbance. As Vertisols cover 335 million hectares worldwide, these findings can be relevant for many regions and ecosystems globally. We highlight the need for similar studies in other soil and habitat types to test whether the presence of deep buried seeds is specific to soils with Vertic characteristics.

Relative importance of region, seasonality and weed management practice effects on the functional structure of weed communities in French vineyards

Winegrowers have diversified their weed management practices over the last two decades changing the structure and the composition of weed communities. Complementary to taxonomic studies, trait-based approaches are promising ways for a better understanding of weed community responses to environmental and agronomic filters. In the present study, the impacts of climate, soil characteristics, seasons and weed management practices (chemical weeding, tillage and mowing) were assessed on weed communities from 46 plots in three French wine-growing regions (Champagne, Languedoc and Rhône valley). These agro-environmental gradients structuring weed communities according to their combinations of traits were highlighted using multivariate analysis (RLQ). The impacts of these filters on Community Weighted Means (CWM) and Community Weighted Variance (CWV) of weed communities were analysed using mixed and null modelling. Our results showed that spatio-temporal and weed management practice variables explained from 13% to 48% of the total variance of CWM (specific leaf area, maximum height, seed mass, flowering onset and duration and lateral spread). Region, seasonality and management practices explained 53%, 28% and 19% of CWM marginal variance, respectively. Weed management impacted CWM and CWV through two main gradients: (i) a soil disturbance gradient with high mechanical disturbance of soil in tilled plots and low mechanical disturbance in chemically weeded plots and (ii) a vegetation cover gradient with high vegetation abundance in mowed plots compared to barer soils in tilled and chemically weeded plots. In Languedoc, chemical weeding filtered weed communities with ruderal strategy trait values (low seed mass, small-stature) while mowed communities were more competitive (higher seed mass, higher stature and lower SLA). In Languedoc and Champagne, tillage favoured communities with high seed mass that increases the viability of buried seeds and high lateral spread values associated to the ability to resprout after tillage. This study demonstrated that trait-based approaches can be successfully applied to perennial cropping systems such as vineyards, in order to understand community assembly to better guide weed management practices.

Soil Seed Bank Persistence Across Time and Burial Depth in Calcareous Grassland Habitats.

Seed persistence in the soil is crucial for population dynamics. Interspecific differences in soil seed mortality could be a mechanism that may stimulate species coexistence in herbaceous plant communities. Therefore, understanding the levels and causes of seed persistence is vital for understanding community composition and population dynamics. In this study, we evaluated the burial depth as a significant predictor of the temporal dynamics of soil seed persistence. We suppose that species differ in this temporal dynamics of soil seed persistence according to burial depth. Furthermore, we expected that burial depth would affect soil seed persistence differently concerning the species-specific type of dormancy, light, and fluctuating temperature requirements for germination. Seeds of 28 herbaceous species of calcareous grasslands were buried in the field into depths of 1, 5, and 10 cm under the soil surface. Seed viability was tested by germination and tetrazolium tests several times for three years. Species-specific seed traits—a type of dormancy, light requirements and alternating temperature requirements for germination, and longevity index—were used for disentangling the links behind species-specific differences in soil seed persistence. Our study showed differences in soil seed persistence according to the burial depth at the interspecific level. Generally, the deeper the buried seeds, the longer they stayed viable, but huge differences were found between individual species. Species-specific seed traits seem to be an essential determinant of seed persistence in the soil. Seeds of dormant species survived less and only dormant seeds stayed viable in the soil. Similarly, seeds of species without light or alternating temperature requirements for germination generally remained viable in the soil in smaller numbers. Moreover, seeds of species that require light for germination stayed viable longer in the deeper soil layers. Our results help understand the ecosystem dynamics caused by seed reproduction and highlight the importance of a detailed long-term investigation of soil seed persistence. That is essential for understanding the fundamental ecological processes and could help restore valuable calcareous grassland habitats.

Seedbank persistence of four summer grass weed species in the northeast cropping region of Australia.

Summer grass weed species are a particular problem in the northeast cropping region of Australia because they are prolific seeders and favor no-till systems. Information on weed seed persistence levels can be used for the development of effective and sustainable integrated weed management programs. A field study was conducted over 42 months to evaluate the seedbank persistence of Chloris truncata, C. virgata, Dactyloctenium radulans, and Urochloa panicoides as affected by burial depth (0, 2, and 10 cm). Regardless of species, buried seeds persisted longer than surface seeds and there was no difference in seed persistence between 2 and 10 cm depths. Surface seeds of C. truncata depleted completely in 12 months and buried seeds in 24 months. Similarly, C. virgata seeds placed on the soil surface depleted in 12 months. Buried seeds of this species took 18 months to completely deplete, suggesting that C. truncata seeds persist longer than C. virgata seeds. Surface seeds of D. radulans took 36 months to completely deplete, whereas about 7% of buried seeds were still viable at 42 months. U. panicoides took 24 and 42 months to completely exhaust the surface and buried seeds, respectively. These results suggest that leaving seeds on the soil surface will result in a more rapid depletion of the seedbank. Information on seed persistence will help to manage these weeds using strategic tillage operations.

Stale seedbed preparation for sustainable weed seed bank management in organic cropping systems

Stale seedbed preparation is a neglected agronomic strategy used to decrease weed seed banks. The experiments aimed to verify the quantity-qualitative seed bank reduction after different soil tillage typologies: rotary cultivator, rotary harrowing and spike tooth harrowing (tillage depth in each case uniformed to about 15 cm). Tillage was carried out during the spring-summer period, with five tillage sequences spaced about 30-40 days. The weed seedbank analysis (10-30 cm) showed that beyond a 10 cm soil depth, the buried seeds were unaffected irrespective of the kind of soil tillage since no seed depletion was observed. In contrast, weed seed bank was heavily depleted in the shallowest soil layer (0-10 cm) due to the germination trigger induced by the soil aeration and by the consequent increase of oxygen availability after tillage. This seed bank reduction, was proportional to the degree of soil crumbling induced by the different tillage methods and it was higher in the case of the smaller soil clods size. Each weed species showed the highest emergence dynamics when soil tillage was carried out during the periods most suitable to meet the respective thermal requirements. Indeed the earliest soil tillage in April triggered germination and emergence of microthermal weeds, while those carried out in May and June triggered the emergence dynamics of weeds characterized by higher thermal requirements. The emergence rate, after the stale seedbed preparation, showed high values overall in the case of deep soil crumbling. In addition the extent of soil crumbling was positively related to the biodiversity of the emerged weed communities. The weed species that were the least sensitive to stale seedbed preparation were those characterized by small seeds and consequently those species would be more difficult to reduce through stale seedbed preparation.

Effects of precipitation and microorganisms on persistence of buried seeds: a case study of 11 species from the Loess Plateau of China

Effects of precipitation and microorganisms on persistence of buried seeds: a case study of 11 species from the Loess Plateau of China