Soil Seed Bank Research Articles

Spatiotemporal variation of common ragweed soil seed bank density in cornfields

AbstractCommon ragweed (CR) (Ambrosia artemisiifolia L.) can reduce agricultural productivity, especially in corn (Zea mays L.) fields. The spatiotemporal variation of the soil seed bank (SSB) of CR is important for understanding the growth potential and control options of this weed. In 2018, we measured SSB density and seed germination characteristics of CR on the margins of cornfields (18 cornfields, each is >1 ha) as well as 2, 5, and 10 m inside the fields from the margin based on the year of CR invasion (2012–2017) in the Yili Valley, Xinjiang, China. From 2016–2018, we studied the effect of eradicating CR plants on reducing the SSB density of CR. Along the cornfield margins, 80.5% of the total CR seeds were viable in the 0‐to‐5‐cm soil layer (SL) after 6 yr of invasion; however, fewer were viable at 2, 5 and 10 m (respectively, 49.5, 44.1, and 42.3%) inside the cornfields. Different modes of SSB accumulation led to different distribution characteristics of the SSB. The increase in the SSB in cornfields was driven by large‐scale seed production of CR along the margins of cornfields. When there was no new CR seed input for 2 yr (in 2018), the density of the SSB at cornfield margins and 2, 5, and 10 m inside the fields decreased by 90.0, 72.9, 75.4, and 74.6%, respectively. Eradicating CR plants before their seeds mature, and doing so for several years, appears to be an effective strategy for controlling CR.

Elevation and micro environmental conditions directly and indirectly influence forests’ soil seed bank communities

The soil seed bank (SSB) plays an important role in determining future community composition and health of forests. The extent to which abiotic conditions alter the abundance and diversity of the future forest composition via modulating the regenerative capacity of the SSB and their relationship with each other is not fully understood. We studied how elevation and abiotic conditions (canopy openness, slope, aspect, soil pH, and a natural gradient of these soil nutrients: total nitrogen [N], total carbon [C], C:N ratio, available phosphorus [P], available potassium [K], calcium [Ca], iron [Fe], magnesium [Mg], manganese [Mn], and sulfur [S]) affect community characteristics, calculated as: (1) seedling abundance, (2) species richness, (3) Shannon-Weiner diversity index, (4) Simpson index, (5) Chao 2 richness estimator, (6) number of species represented by only one individual, and (7) number of species that occur only in one plot. We used soils sampled in 13 1-ha plots along an altitudinal gradient from 400 to 1850 m above sea level. We determined both direct and indirect causal relationships between abiotic factors and SSB community characteristics using linear mixed models and structural equation modeling. Increased elevation and canopy openness resulted in lower species richness and diversity as well as fewer rare species. However, greater canopy openness resulted in higher abundance. Abundance and richness of the SSB were lower in steeper slopes, but this negative effect appeared to be along an indirect pathway through soil pH and nutrients such as soil Mn and S. Soil P had a significant negative relationship with SSB characteristics for all indices evaluated here, except for SSB abundance, which was positively affected by increased soil pH. Our results highlight the role of abiotic factors in forest regeneration and resilience through their influence on the soil seed bank community. This study is one of the very first to provide data on the SSB along a wide elevational range in subtropical forests, and can be the basis to assess the regeneration potential and health of the study region.

Soil seed bank characteristics in relation to different shrub species in semiarid regions

AbstractLittle information is available about the effects of different species of shrubs on the composition of the soil seed bank (SSB) in the semiarid regions. We determined the role of three dominant shrub species on SSB characteristics and evaluated their potential for their possible use in rangeland restoration projects. Fifteen sites, each containing three shrub species (Amygdalus scoparia, Daphne mezereum and Ebenus stellata) and a herbaceous patch (control) in close proximity, were sampled and their SSB density, species richness and diversity at 0–10 cm depth were determined. The results showed that the density of the SSB was highest under A. scoparia and lowest in the control. The highest SSB density of grasses was found under A. scoparia, while the highest SSB density of forbs was found under E. stellata. Species diversity of the SSB was significantly greater under E. stellata than under the other shrubs and control. This study revealed that the extent to which shrubs affected SSB characteristics did not only depend on the presence of shrubs, but also on the species of shrubs. These different roles of different species of shrubs on SSB are advised to be considered in the restoration of degraded areas through the SSB in the semiarid areas. In the case of changing management type from intensive grazing to extensive grazing or non‐grazing, the role of different shrub species in the conservation herbaceous species through their SSB can be different.

Continuous grazing disrupts desert grass-soil seed bank composition under variable rainfall

Long-term field studies help unveil mechanisms of grass soil seed bank (SSB) persistence and resilience. We wonder whether grazing is a disruptive force that changes grass SSB composition and size, while heavy rainfall is a positive bottom-up force that restores the grass SSB in grazed areas of the Monte desert, Argentina. We used core sampling to study the grass SSB in cattle-free (17 year) and grazed (10 year) grasslands. The SSB size in cattle-free sites usually responded in a continuous positive fashion to rainfall, and the proportion of palatable grasses in the SSB was similar among years. Most grass species formed a transient SSB, but the presence of a stand of perennial plants would prevent their local extinction. In contrast, the SSB size in the grazed habitats showed a threshold response to rainfall (i.e. it did not increase under low-moderate rainfall), the seeds of palatable grasses were always scarce, and the proportion of seeds of less palatable grasses increased under extreme rainy conditions. Seed production from grasses that grew tillers from axillary buds during a drought was zero, suggesting that the bank of plants could have a role in the replenishment of the grass SSB only in mesic years. Within the time span assessed here, continuous heavy grazing together with scarce as well as heavy rainfall were disruptive forces that reduced the number and proportion of seeds from palatable grasses in the SSB, which are also the species preferred by seed-eating animals.

Ambrosia trifida L. - trolisna ambrozija

Ambrosia trifida L. (AMBTR, fam. Asteraceae/Compositae) is native to North America. It was introduced accidentally to Europe at the end of the 19th century, with contaminated animal feed and seeds for planting. Today A. trifida is present in ruderal and agricultural habitats of many European countries (France, Italy, Germany, Russia, Spain, Romania, Slovakia, Czech Republic, Poland, Serbia, Bulgaria, etc.). Giant ragweed was detected for the first time in 1981 in Serbia (site Čoka). Over the following period it disappeared from this site, but was recorded again in 2006 in another site (central Bačka: Despotovo, Kucura, Savino Selo, Ravno Selo, Ruski Krstur). Currently in Serbia it has the status of an alien naturalized weed species. This summer annual plant can grow up to 6 m in height and exhibits a high degree of morphological and reproductive plasticity in response to encroachment by neighboring plants. It is present in disturbed habitats, such as agriculture fields, where it plays the role of the dominant species throughout the entire growing season. In most cases, leaves are opposite and always simple and generally have 3 distinct lobes but can also have as many as 5. It is a diploid (2n = 24), meso-hygrophilic species, preferring wet habitatse and can tolerate a wide variety of soil types. Also, this is a monoecious plant, where male and female flowers are separated on the same individual. A. trifida can hybridise with A. artemisiifolia (A. x helenae Rouleau, with 2n= 27 and 2n= 33), but this hybrid has been described as sterile. Compared to other summer annual species, A. trifida is among the first to emerge in early spring, at optimal temperatures from 10-24°C. Under optimal environmental conditions, giant ragweed produces around 1,800 (max 5,100) seeds plant-1. It flowers and bears fruit from July to September (October).The pollen of this species has allergenic potential. Additionally, in the USA and Canada giant ragweed populations have developed resistance to acetolactate synthase inhibitor herbicides and glyphosate. Giant ragweed can be a problematic weed in row crops (corn, soybean, sunflower, sugerbeet) and vegetables. In A. trifida the control measures should prevent further spread, and existing populations should be controlled by integrated weed management practices. Furthermore, A. trifida has a relatively low fecundity, a transient soil seedbank and a high percentage of non-viable or low-survivorship seeds, which are features that may have constrained its establishment and spread in the current environmental conditions in Serbia.

Rehabilitation of waste rock piles: Impact of acid drainage on potential toxicity by trace elements in plants and soil

The restoration of mining areas, in particular if they are located near towns or villages, is essential to reduce their potential risks for human health and to minimize their visual impacts. In this study, we assess the rehabilitation of a waste rock pile adjacent to the town of Tharsis (SW Spain). We measured vegetation cover and its diversity, and chemical composition of plants and soil, twelve years after remediation by lime amendments, added topsoil and planted vegetation. In general, the applied measures were successful covering with woody vegetation the upper part of the waste rock pile, and providing a greening visual landscape for the town nearby. The most abundant species were the gum rockrose (Cistus ladanifer) and the legume shrub Retama sphaerocarpa, this latter species most probably introduced in the seedbank of the added topsoil. Also in the soil seedbank, probably arrived the invasive Acacia saligna, of fast growth. In contrast, the lower part of the slopes was almost devoid of vegetation. We interpret that partial failure in the rehabilitation process as due to the acid mine drainage, which caused downslope a decrease of soil pH and increased availability of trace elements, thus impeding growth and establishment of plants. In addition, some plants, like C. ladanifer, growing at the base of the rock pile, had concentrations of Cd above the maximum tolerable level for animals, therefore representing a toxicity risk. Finally, we propose here an alternative technique to restore waste rock piles, by sorting and selectively handling the extractive wastes, thus reducing infiltration rates, seepages and the negative effect of the acid mine drainage. Those modified waste rock piles will be rehabilitated by the addition of topsoil and planted vegetation, as successfully worked out in the upper slopes of the study site.

Modeling smallholder agricultural systems to manage Striga in the semi-arid tropics

Across southern Africa (SA), significant maize yield losses are attributed to invasive and parasitic weeds. Abundance of Striga (Striga asiatica) has become more frequent in smallholder farms (<2 ha) in the past decade. Various Striga control practices (SCPs) have been disseminated across SA, yet often, without decision support tools to inform extension officers and researchers which ones are most appropriate for smallholder contexts. System dynamics modeling (SDM) provides an opportunity to evaluate the efficacy of SCPs across multiple seasons in different agroecosystems and their associated environments. We developed a SDM to evaluate the long-term efficacy of four SCPs popularly used in maize-based cropping systems. Observations from studies outlining local soil seedbanks, emergence and flowering rates in farmer fields were used to calibrate the SDM. Model simulations indicate that while a combination of SCPs are necessary to manage the weed, future research should focus on developing smallholder-adapted SCPs that address the attachment stage of the weed's lifecycle (e.g., timely manure application) rather than its germination, emergence or flowering stages. Given the devastating effects S. asiatica has had on food security in Malawi and across SA, it is imperative to develop decision support tools like systems models to evaluate SCPs for smallholders. Models that do not capture the underlying mechanisms driving S. asiatica infestations may provide extension officers with potentially misleading information, and subsequently, the delivery of ineffective SCPs.

Dispersal and recruitment limitations in secondary forests

AbstractAimsSecondary forests are expanding rapidly in tropical regions and could play an important role in conserving native biodiversity and stabilising global climate. The recovery rate of plant communities in secondary forests varies considerably due to mechanisms associated with seed dispersal and recruitment dynamics. We explored these mechanisms along a chronosequence of tropical secondary forests in an agricultural landscape that was extensively cleared.LocationWe explored these mechanisms along a chronosequence of secondary forests in tropical Australia.MethodsWe used selected plant traits to characterise plant species and compared community composition between demographic stages (i.e. soil seedbank, understorey and overstorey) and forest age categories. We collected soil samples to assess seedbank composition and used quadrants and transects to assess understorey and overstorey plant community composition at each site.ResultsFor all demographic stages, we found that young (4‐12 years) and intermediate‐aged forests (16‐20 years) were dominated by early successional, small‐seeded species and traits associated with disturbed forests. In old secondary forest (23‐34 years) some traits associated with late successional stages were present (e.g. large seeds, trees). However, the traits and species composition of mature forests remained distinct from all secondary forests. Across the chronosequence, forest age and demographic stage were significant factors in discriminating species and trait composition between forest sites. We found clear plant community similarities within demographic stages, despite the forest age differences. This suggests stronger limitations to dispersal and recruitment between demographic stages than between forest ages.ConclusionsOur results show that secondary forests in this region assemble slowly with dispersal and recruitment limitations constraining their recovery. Although a successional transition in species and plant traits composition along the chronosequence is clear, similarities to mature forests remain low. The slow recovery of late successional and large‐seeded species in these secondary forests suggests that active restoration of such species may be necessary if we want to enhance the capacity of these forests to conserve native biodiversity.

Germination biology of three populations of Navua sedge (Cyperus aromaticus)

AbstractNavua sedge [Cyperus aromaticus (Ridley) Mattf. &amp; Kük.] is an aggressive perennial sedge native to equatorial Africa that has become problematic in many Pacific islands and wet, tropical Queensland, Australia. It has had a significant impact on the livestock-grazing industry, sugarcane (Saccharum officinarum L.) and banana (Musa acuminata Colla) plantations, and various other ecosystems. A laboratory-based research investigation was conducted to understand germination and emergence requirements under various environmental conditions of three geographically varied populations sourced from South Johnstone (SJ), Mackay (M) and Nyleta Creek (NC) in Queensland. Germination was identified to be stimulated by light, with no germination recorded under darkness. Populations SJ and NC had optimal germination at alternating temperatures of 25/15, 30/20, and 35/25 C, whereas population M had optimal germination at 25/15 and 30/20 C. All populations recorded greater than 85% germination at all pH levels tested. Seeds of population SJ were more sensitive to salinity compared with populations M and NC, with SJ showing no germination at 100 mM, whereas populations M and NC had 23% and 9% germination, respectively. An inverse relationship was observed between osmotic potential and germination, with no germination recorded at osmotic potentials below −0.8 MPa in any population, indicating moisture availability is a critical requirement for germination. Exposing seeds to 120 C radiant heat completely inhibited germination in populations M and NC, whereas 3% of population SJ germinated following a 180-s exposure at 120 C. Seedling emergence decreased as planting depth increased. Emergence was greatest for seeds on the soil surface or at 0.5-cm burial depth, consistent with germination being stimulated by light. Knowledge of these biological characteristics of C. aromaticus seed germination will assist in investigation of suitable control actions for this species, particularly in the early stage of its invasion into new areas, and will contribute to significant reduction in the soil seedbank.

Best served deep: The seedbank from salvaged topsoil underscores the role of the dispersal filter in restoration practice

AbstractQuestionsGlobally, ecological restoration is required to restore degraded landscapes and to contribute to biodiversity conservation. Ecological theory suggests that manipulating dispersal, abiotic and biotic filters limiting plant re‐establishment will improve restoration outcomes. Here, we manipulated spread depth of soil containing a salvaged soil seedbank (dispersal filter), soil compaction (abiotic filter) and herbivore grazing (biotic filter) in a topsoil transfer experiment to test their effects on restoration success.LocationBanksiawoodland of the Swan Coastal Plain, Western Australia.MethodsTopsoil (upper ~7 cm) with its seedbank was removed from a donor site (20 ha) of recently cleared native vegetation and transferred to six recipient restoration sites (16 ha). Deep (10 cm thick) and shallow (5 cm thick) layers of topsoil were applied in a fully factorial experiment, with and without soil ripping and fencing, respectively. We analysed emergence, survival and functional types (alien/native, life form, fire response) of all vascular plant species for two consecutive years after topsoil transfer.ResultsThe most successful restoration treatment was deep topsoil with a mean density of 14.3 m−2native perennial germinants in year one and 7.3 m−2in year two. Application of deep topsoil increased native seedling emergence by 34% and decreased weed density by 21% compared with shallow topsoil. Overall seedling survival across the two‐year period was unaffected by filter treatments (range 0.6%–5%). After two years, the resulting plant community was 6%–38% weed species and of native perennial species, 12%–48% were capable of resprouting.ConclusionsManipulation of the dispersal filter alone, that is deep topsoil application, can lead to near‐equivalent native species number emerging on restoration sites as compared to pre‐cleared woodland. However, more research is required to test additional restoration tools to improve survival of biodiverse plant communities. For example, targeted herbicide application coupled with soil ripping to improve weed management and native seedling establishment.

Legacy effects of non-native Cytisus scoparius in glacial outwash soils: Potential impacts to forest soil productivity in western Washington

Scotch broom (Cytisus scoparius (L.) Link) is a highly competitive, nonnative, leguminous shrub species of major concern in coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) forests of the Pacific Northwest that has potential to impact long-term soil productivity. We conducted a bioassay to assess the potential for legacy effects on soils (e.g., soil nutrient effects, soil seedbank, etc.) following Scotch broom removal and the potential for recovery over time. The bioassay was conducted using glacial-outwash soils from an existing Long-Term Soil Productivity study near Matlock, WA, USA, where Scotch broom had been removed or kept out for 0 (broom present), 4, 10, or 14 years. Soils from each broom removal duration were combined with fertilizer treatments to assess mechanisms of response of three native plant species: yarrow (Achillea millefolium L.), Roemer’s fescue (Festuca idahoensis Elmer ssp. Roemeri), and coast Douglas-fir. There was evidence for negative soil legacy effects on Douglas-fir growth and biomass, which decreased with time since broom removal. Responses to the fertilizer treatments indicated the effect was not associated with reduced nutrient availability. In contrast, both yarrow and Roemer’s fescue had significantly greater biomass in soil from where broom was recently present, which decreased with time since broom removal. Responses to the fertilizer treatments indicated that this positive legacy effect is associated with nutrient availability, likely increased N. Soils from 0 and 4 years since broom removal were estimated as having the potential to produce over 578,500 Scotch broom germinants ha−1. Our results demonstrate the potential for both negative and positive soil legacy effects of broom depending on the responding plant species. Combined effects of negative soil legacies and a large and viable seed bank from Scotch broom create growing conditions likely to hinder long-term productivity of Douglas-fir.

The resilience of weed seedbank regulation by carabid beetles, at continental scales, to alternative prey

Carabids are generalist predators that contribute to the agricultural ecosystem service of seedbank regulation via weed seed predation. To facilitate adoption of this ecosystem services by farmers, knowledge of weed seed predation and the resilience of seedbank regulation with co-varying availability of alternative prey is crucial. Using assessments of the seedbank and predation on seed cards in 57 cereal fields across Europe, we demonstrate a regulatory effect on the soil seedbank, at a continental scale, by groups formed of omnivore, seed-eating (granivore + omnivore) and all species of carabids just prior to the crop-harvest. Regulation was associated with a positive relationship between the activity-density of carabids and seed predation, as measured on seed cards. We found that per capita seed consumption on the cards co-varied negatively with the biomass of alternative prey, i.e. Aphididae, Collembola and total alternative prey biomass. Our results underline the importance of weed seedbank regulation by carabids, across geographically significant scales, and indicate that the effectiveness of this biocontrol may depend on the availability of alternative prey that disrupt the weed seed predation.

Abandoned corrals: colonization and vegetation recovery of ephemeral habitats in silvo-pastoral systems

Abstract Aims Management of silvo-pastoral systems in planted and natural forests in semi-arid Mediterranean regions often employs seasonal night corrals for animal protection. This management system changes the spatial distribution of animal excreta, resulting in a net transfer of soil mineral resources and their accumulation in the corrals. After abandonment, corrals are colonized by ruderal species, becoming focal sources for their spread in the forest. We aimed to implement a rational management of seasonal sheep corrals based on a better understanding of the vegetation processes occurring in abandoned corrals, in order to alleviate their negative impact in the forest. Methods Relationships between temporal changes in the vegetation, the soil seed-bank and levels of soil nutrients were studied in a chronosequence of abandoned sheep corrals and compared with nearby reference plots in planted Eucalyptus forests grazed by sheep in the semi-arid North-Western Negev, Israel. The region has a bi-seasonal Mediterranean climate, with high dominance of annual species in the grazing range. Important Findings Abandoned sheep corrals were colonized by seeds of ruderals originating in older abandoned corrals. Subsequent successional changes occur at a slow rate, driven by the depletion of soil resources in the abandoned corrals, and were still in progress 20 years after abandonment. Ruderals were gradually replaced, first by taller grasses and followed by short grasses, but most forbs and particularly geophytes did not recover during this period. Recovery of the original herbaceous vegetation in the corrals was through seed dispersal from the surrounding vegetation, not from the original soil seed-bank remaining in the corrals after abandonment. Ruderal species in the grazed, planted forests behave as patch-tracking metapopulations. Their persistency depends on constant creation of new corrals compensating for the gradually dwindling populations in older abandoned corrals, and on the availability of dispersal vectors.

Effects of herbicide management practices on the weed density and richness in dicamba-resistant cropping systems in Indiana

AbstractThe addition of dicamba as a weed control option in soybean [Glycine max (L.) Merr.] is a valuable tool. However, this technology must be utilized with other herbicide sites of action (SOAs) to reduce selection pressure on weed communities and ensure its prolonged usefulness. A long-term trial was conducted for 7 yr in Indiana to evaluate weed community densities and species richness with four levels of dicamba selection pressure in a corn (Zea mays L.)–soybean rotation. Monocot densities and richness increased over time in the dicamba-reliant treatment. Dicot densities in the dicamba-reliant treatment declined over time, but dicot richness increased. The soil weed seedbank was affected by the varying herbicide strategies. The dicamba-reliant strategy had greater than 43% higher total weed density than all other treatments, primarily due to having a monocot density that was at least 71% higher than the other treatments. The fully diversified strategy with eight SOAs and residual herbicides used every year had the lowest total weed species richness in the soil seedbank, which supported the in-field observations.

Banco de sementes do solo em três fitofisionomias de cerrado no leste de Mato Grosso do Sul

O objetivo do trabalho foi avaliar a composição do banco de sementes do solo de três fitofisionomia do Bioma Cerrado buscando responder as seguintes hipóteses: (1) a diversidade do banco de sementes do solo reflete a diversidade da fitofisionomia nativa ao qual está inserido; (2) o banco de sementes do solo dessas fitofisionomias têm potencial para restauração de áreas degradadas. Para avaliar estatisticamente banco de sementes do solo foi utilizado um delineamento inteiramente casualizado (DIC) com quatro tratamentos e trinta repetições (4 x 30): T1- testemunha (areia lavada e autoclavada); T2- banco de sementes do solo do Cerrado Stricto sensu (CS); T3-banco de sementes do solo do Cerradão (CD); T4- banco de sementes do solo da Mata de Galeria (MG). O banco de sementes do solo apresentou uma representatividade de 1.240 indivíduos, distribuídos nas três áreas. Nesse estudo, rejeita-se a hipótese de que a diversidade do banco de sementes do solo é um reflexo da vegetação ao qual está inserido, sendo evidente uma dissimilaridade do banco de sementes do solo entre as três áreas avaliadas. Sugere-se que essas diferenças encontradas na diversidade florística do banco de sementes do solo podem ser influenciadas pelas perturbações antrópicas de áreas adjacentes e pelas características edafoclimáticas como tipo de solo, umidade e relevo. A segunda hipótese pode ser atendida se o banco de sementes do solo for utilizado para conferir um rápido recobrimento do solo, no entanto, deve ser aliado com enriquecimento de espécies nativas zoocóricas características da vegetação a ser recuperada.

Soil seedbank: Old methods for new challenges in agroecology?

AbstractThe weed soil seedbank is of interest in agroecosystems as a major source of weed infestation in fields and as a reservoir of plant and seed‐feeder diversity. A seedbank is a characteristic of annual plants and has been the focus of numerous studies, as it reflects the past aboveground vegetation and is the reservoir of the future vegetation. Therefore, it potentially can be used to evaluate the past, present and future annual weed communities. The goal of this paper was to provide guidelines to help researchers to do a weed seedbank survey. Through a qualitative review of 60 weed seedbank articles, we investigate why and how the seedbank has been studied in agronomy. It shows that seedbank studies have been performed to address the following four major objectives: (a) the assessment of weed management practices on weed communities; (b) the relationship between seedbank and aboveground vegetation; (c) the study of composition and diversity of seedbank in a given area; and, (d) the quantification of seedbank as a food resource for wildlife. Because the analysis highlighted a wide range of methodologies to estimate the seedbank, we critically reviewed them. We show that the selected methodology strongly affects the seedbank estimate. Nevertheless, in our sample of research articles, the analysis revealed that the choice of the methodology was not always justified in terms of achieving a particular scientific goal, but was often determined by the resources available for the experiment (e.g., workload). While studying the soil seedbank remains of interest for scientists (proved by the amount of recent publications), it is time consuming and requires considerable botanical skill. Innovative methods of estimation are scarce and novel methodological developments are needed to increase the quality and reliability of the data obtained.

Herbaceous seeds dominates the soil seed bank after long-term prescribed fire, grazing and selective tree cutting in savanna-woodlands of West Africa

The soil seed bank (SSB) is an important source of resilience for plant communities subjected to disturbances. This study aimed to identify characteristics of the SSB, its relationship with aboveground vegetation (AGV), and its significance for restoration of vegetation in West African savanna-woodlands. Data were collected from two long-term factorial experiments established in 1992 in Burkina Faso to examine the long-term ecological effects of grazing, early fire, selective tree cutting on savanna-woodland ecosystem. A total of 1920 soil samples were taken from three soil layers (i.e. 0-3 cm, 3–6 cm and 6–9 cm) and the SSB was assessed using the seedling emergence technique. The emerged seedlings were dominated by non-woody taxa. Only two woody species that were Flueggea virosa and Mitragyna inermis emerged, showing that woody species feature little in the SSB. The SSB density and richness decreased significantly with soil depth. Non-metric multidimensional scaling (NMDS) ordination indicated a lack of correspondence between the AGV and SSB. The results suggest site-specific responses to disturbance also following long-term disturbance, the SSB will be ineffective in regenerating the remnant vegetation of West African savanna-woodlands. Hence, ensuring the resilience of West African savanna woodland ecosystems will require targeted introductions (i.e. planting and seeding) of indigenous species and a reduction in on-going disturbances.

Seed traits determine species' responses to fire under varying soil heating scenarios

Abstract Many plant species in fire‐prone environments maintain persistence through fire via soil seedbanks. However, seeds stored within the soil are at risk of mortality from elevated soil temperatures during fire. Seeds may be protected from fire‐temperature impacts by burial, however, those buried too deeply may germinate but fail to emerge. Thus, successful post‐fire seed regeneration is contingent upon a trade‐off between burial depth and survival through fire. We examined the relationships between seedling emergence behaviour, seed survival and soil temperatures during fire in 13 native and four non‐native woodland species in southwestern Australia. We assessed total seedling emergence per depth, maximum seedling emergence depth and seedling emergence speed from seeds planted at eight depths (0, 1, 2, 3, 4, 5, 7, 10 cm). Soil temperatures were quantified using distributed temperature sensing in optic fibre (DTS), measured continuously between 1 and 10 cm in depth (temperatures were subsequently categorized into 1 cm increments for analysis) during five experimental fires in beds with fine fuels manipulated between 8 and 20 t/ha. Using seed survival and emergence success relative to soil temperatures, we determined vulnerability of seedling emergence relative to soil temperatures generated by combustion of fuel quantities typically observed in woodlands. Maximum depth of emergence varied between species from 2 to &gt;10 cm, with a positive linear correlation to seed mass. Maximum soil temperatures from the two highest fuel masses exceeded seed lethal thresholds (T50—representing temperatures lethal to 50% of seeds) of at least five species. Lethal temperatures were exceeded at all potential emergence depths for all three grass species, and all four non‐native species studied. Of the remaining 10 species, temperatures did not exceed the lethal thresholds under any of the fuel mass levels tested. We found no relationship between lethal temperature thresholds and maximum emergence depth. Our data demonstrate that seeds exhibit variation in their response to soil heating and capacity to emerge from depth, with three distinct functional responses amongst our study species, which enable persistence through, and recruitment following, fire. Such variation in species attributes and fuel mass may lead to heterogeneity (within fires) or divergent trajectories (among fires) in community response under changed fire regime. A free Plain Language Summary can be found within the Supporting Information of this article.

Evaluation of Preemergence and Postemergence Herbicide Programs on Weed Control and Weed Seed Suppression in Mississippi Peanut (Arachis hypogea)

Weed control and reducing weed seed deposition to the soil seedbank is a challenging issues for Mississippi peanut producers. Research was established during 2017 and 2018 at the Delta Research and Extension Center in Stoneville, Mississippi, to evaluate herbicide programs for weed control and reducing weed seed production in Mississippi peanut production. Treatments were combinations of acetochlor, clethodim, flumioxazin, lactofen, paraquat, and S-metolachlor with their respective adjuvants if needed. Treatments were applied PRE, two to three weeks after emergence (EPOST), and/or four to five weeks after emergence (MPOST). All treatments included a PRE application followed by (fb) application of EPOST and/or MPOST application. Flumioxazin PRE fb lactofen plus clethodim MPOST provided greater than or equal to (≥) 88% control of barnyardgrass, hemp sesbania, Palmer amaranth, pitted morningglory, and prickly sida. Additionally, this treatment reduced total weed seed production 88% compared to the nontreated control. Flumioxazin PRE fb lactofen plus clethodim EPOST fb acetochlor MPOST provided similar weed control and peanut yield as flumioxazin PRE fb lactofen plus clethodim MPOST. This treatment reduced total weed seed production 93%. Treatments containing PRE, EPOST, and MPOST herbicide applications provided the best season-long control of weeds and weed seed suppression in Mississippi peanut.

Influence of flooding period and seed burial depth on Palmer amaranth (Amaranthus palmeri) seed germination.

Flooding throughout fall and winter months is an effective practice for rice (Oryza sativa L.) straw decomposition, soil seedbank depletion, and waterfowl habitat in Mississippi. Nevertheless, limited research is available regarding the effects of fall-winter flooding and seed burial depth on Palmer amaranth (Amaranthus palmeri S. Wats.) seed germination. The objective of this study was to evaluate the effect of flooding period and seed burial depth on A. palmeri seed damage and germination in three different soil textures in Mississippi. Amaranthus palmeri seed damage was greater when seeds were buried in sandy loam compared to silt loam soil textures. An interaction between flooding period and seed burial depth was present for A. palmeri seed germination. Flooding periods of 1-month (at 0 and 15 cm burial depth) and 2 months (at 0 cm burial depth) provided similar A. palmeri seed germination compared to no-flooding (at 0 cm burial depth). In addition, flooding periods of 3, 4, and 5 months reduced A. palmeri seed germination by 10, 10 and 14 percentage points at 0 cm burial depth, and 36, 40, and 41 percentage points when seeds were buried at 15 cm, respectively, across all soil textures. This research demonstrates that flooding for 3, 4, and 5-months throughout fall and winter is an effective cultural practice to increase soil seedbank depletion through reduced germination potential to help manage herbicide-resistant A. palmeri populations in sandy loam, silt, and silt loam soil textures. © 2020 Society of Chemical Industry.