Seedling Emergence Method Research Articles

Weed seedbank as influenced by tillage and herbicide in direct seeded rice‐mustard cropping sequence in lateritic soil of eastern India

AbstractThe above‐ground community dynamics of weeds represent the soil weed seedbank in an agro‐ecosystem. Hence, understanding the seedbank will offer an idea for future weed management tactics. We aimed to determine the density of weed seedbank and emergence of major weeds in direct seeded rice (DSR) (Oryza sativa L.)—mustard (Brassica campestris L. var. yellow sarson) cropping sequence under varied tillage and herbicide combinations. The present study on weed seedbank was conducted using seedling emergence method after collecting the soils at the harvest of mustard at the completion of 2 years field experimentation. The experiment was conducted in split‐plot design with two tillage practices [zero tillage (ZT) and conventional tillage (CT)] in main plot and eight weed management practices in DSR [oxadiargyl followed by (fb) bispyribac‐sodium, penoxsulam + cyhalofop‐butyl, oxadiargyl fb penoxsulam + cyhalofop‐butyl, fenoxaprop‐p‐ethyl + ethoxysulfuron, oxadiargyl fb fenoxaprop‐p‐ethyl + ethoxysulfuron, pendimethalin fb bispyribac‐sodium, unweeded control, and weed free check] as subplot. The carry‐over effect of tillage and weed management practices were recorded in mustard crop. Seed emergence study revealed that ZT reduced the emergence of grassy weeds (by 13.7%) and total weed emergence (19.5%) in comparison to the CT (p < 0.05). However, emergence of broadleaf weeds was 24.5% higher in ZT than in CT. The higher infestation was recorded for Ludwigia parviflora (Jacq.) Raven under penoxsulam + cyhalofop‐butyl, fenoxaprop‐p‐ethyl + ethoxysulfuron, Cyperus iria (L.) under fenoxaprop‐p‐ethyl + ethoxysulfuron, and Eleusine indica (L.) Gaertn. under pendimethalin fb bispyribac‐sodium, oxadiargyl fb bispyribac‐sodium. Sole application of post‐emergence (POE) herbicide decreased the total weed emergence by 22.2%–28.1% than unweeded control (p < 0.05). Whereas, sequential application of PRE + POE herbicides decreased the total weed emergence by 32.8%–36.9% than unweeded control (p < 0.05). Notably, sedge weeds such as Cyperus iria (L.) and Fimbristylis miliacea (L.) Vahl were lower in ZT than in CT under herbicide treated plots (by 66.6%–84.3%) than unweeded control. Thus, ZT with oxadiargyl 90 g a.i. ha−1 fb fenoxaprop‐p‐ethyl + ethoxysulfuron (90 + 15 g a.i. ha−1) as tank‐mix can be effectively used to lower the weed seedbank density vis‐à‐vis managing complex weed flora in DSR and rice‐mustard cropping sequence.

Soil seed bank dynamics of two invasive alien plants in Nigeria: implications for ecosystem restoration.

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 such as 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- and U. lobata-invaded habitats and -non-invaded habitats making a total of 30 sites. We collected 200 soil samples from 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 when 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 us 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.

Snow, fire and drought: How alpine and treeline soil seed banks are affected by simulated climate change.

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. 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. 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. 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.

Facilitation by Haloxylon persicum Shrubs Enhances Density and Richness of Soil Seed Bank of Annual Plants in a Hyper-Arid Ecosystem.

The soil seed bank is an essential functional component of plant communities. In arid ecosystems, the island-like distribution of shrubs influences the spatial distribution of the soil seed bank. Very little is known about seed banks in deserts of the Middle East. The present study aimed to evaluate the facilitative effects of Haloxylon persicum shrubs on the soil seed bank of annual plants in a sandy desert region in northwestern Saudi Arabia during two consecutive growing seasons (2017-2018 and 2018-2019) with contrasting rainfall. A total of 480 soil samples at 12 stands were collected from two microhabitats, under shrubs and in open areas, soon after the two growing seasons. The germinable seed bank of annual plants was estimated by controlled seedling emergence method. Shrubs significantly facilitated the accumulation of seed bank beneath their canopies after the two growing seasons. In both microhabitats, the size and species richness of soil seed bank were significantly greater after the wet growing season (2018-2019) than following the dry season (2017-2018). The facilitative effects of shrubs were greater following the moister growing season than after the dry season. The effect of shrubs on seed bank-annual vegetation similarity varied between growing seasons, being greater in shrub interspaces than beneath shrub canopies for the dry growing season, while during the wet season, the similarity of the seed bank with standing annual vegetation was greater in sub-canopy microhabitat than in bare soil.

Is endozoochoric seed dispersal by large herbivores an evolutionary adaptation? Revisiting the Janzen's ‘Foliage is the fruit’ hypothesis

Many plant species develop fruits to attract animals that will eat them and then disperse the seeds. However, there are many plant species, whose seeds are dispersed endozoochorically, but their fruits are not particularly attractive to animals. The “Foliage is the fruit” (FF) hypothesis proposes that entire biomass of the plant exists to encourage herbivores to eat it, in order to enhance seed intake and dispersal (Janzen, 1984).We tested the FF hypothesis by combining the results from the greenhouse seedling emergence method (GR) and DNA-metabarcoding of plant remnants in faeces of European moose (Alces alces L.). We processed 665 samples by the GR and 429 by the MB method, hypothesizing that if the safe passage of seeds through the gut of a large herbivore is the result of an evolutionary adaptation to endozoochoric dispersal, then the species composition of plants revealed by the two methods should largely overlap and the abundance of seedlings revealed by the GR method should be positively correlated in time with the read abundance of DNA of the same species. The large discrepancy between the lists of species detected by DNA metabarcoding and the GR method argues against the FF hypothesis. However, in the case of Urtica dioica, Lysimachia vulgaris and Lythrum salicaria, some clues of evolutionary adaptation to endozoochoric dispersal were revealed for: 1) their foliage is attractive to herbivores; 2) seeds are small, rounded in shape, yielded in large numbers and pass safely through the herbivore's gut; 3) the abundance of seeds (seedlings) was significantly and strongly influenced by the abundance of the plant biomass (DNA reads) in dung samples; 4) peaks in seed abundance and biomass consumption coincided in time. However, it should be considered that moose's diet is mostly composed of woody browse, which makes this animal not an optimal model for testing the Janzen's hypothesis and studies on typical grazers are needed in this respect.

Effect of wild boar disturbances on the soil seed bank in alpine plant communities

AbstractSoil seed bank (SSB) determines essential ecological processes by maintaining species diversity and recovering damaged plant communities, and supports conservation of lost plant species. Nevertheless, the variation of SSBs, their densities, and composition changes when accompanied by wild boar disturbances are scarcely studied in sensitive habitats such as alpine grasslands. The aim of this study is to assess the effect of wild boar rooting on SSB characteristics. Five plant communities were selected and four disturbed patches in each community were recognized in alpine grassland, Albors Mountain Chain, Iran. SSB density, richness, diversity, evenness and similarity with aboveground vegetation were compared between disturbed and adjacent undisturbed patches. In total 80 soil cores in each community, 40 disturbed and 40 undisturbed were collected and transported to the greenhouse. The seedling emergence method was used to identify and quantify seeds from the germinable seed bank. The results showed that, totally, the SSB within disturbed patches was smaller than in undisturbed patches. Wild boar (Sus scrofa) rooting decreased SSB density, richness and diversity in all plant communities. We found that rooting homogenized SSBs in disturbed patches as indicated by the Pielou evenness index. The results suggested a deep alteration of the structure of seed banks by wild boar rooting, which in turn, vegetation recovery did not rely on SSBs after disturbances. In order to reduce wild boar rooting damage, a large reduction in wild boar abundance is suggested.

Endozoochorous seed dispersal by Korean water deer (Hydropotes inermis argyropus) in Taehwa Research Forest, South Korea

Endozoochorous seed dispersal by ungulates can facilitate the dispersal of seeds over long distances. Endozoochorous seed dispersal can also result in the ecological filtering of plant species by dispersing plant seeds with distinctive traits. The Korean water deer (Hydropotes inermis argyropus) is a potential long-distance seed dispersal vector in lowland areas of South Korea. In this study, to test the endozoochorous seed dispersal role of Korean water deer in forested areas, we collected 202 fresh fecal pellet group samples in Taehwa Research Forest, Gwangju City, Gyeonggi Province, South Korea. Additionally, we conducted a vegetation survey to compare the traits of dispersed seeds from feces with the seed traits of flora in the study site. To test whether the composition of species traits dispersed by endozoochory is consistent with that of lowland areas, which consist of forested hills, arable land, and wetlands, we compared the results with a former study conducted in the lowlands. From the seedling emergence method applied to feces, we found a total of 22 species and 115 seedlings. Among 202 fecal pellet groups, 19.8% had at least one germinable seed. Species of forbs, with small-sized seeds (≤2 mm in length), from open habitat, and seeds without special morphology for dispersal are most frequently dispersed through Korean water deer endozoochory. These traits were consistent with the former endozoochory study conducted in a lowland area, irrespective of the different available flora. Therefore, we suggest that deer can potentially disperse seeds with the aforementioned traits to forest plant communities, acting as a consistent ecological filter through endozoochory.

Precipitation regulates the livestock dung seed bank through above ground vegetation productivity in the Qaidam basin

AbstractThe livestock dung seed bank (DSB) plays an important role in the regeneration and sustainability of grasslands in grazing ecosystems. As global precipitation patterns change, the productivity of the above ground vegetation (AGV) in semiarid and arid regions may be substantially affected, as will both the size and composition of the livestock DSB. However, the effects of altered precipitation patterns remain to be determined. Dung was collected for three consecutive years (2018–2020) from horses, cattle and sheep in the desert region of the Qaidam basin, China. The seedling emergence method was used to examine species richness and seed density in the DSB, and the structure and composition of the DSB and the AGV were also investigated. Combined with precipitation data, a structural equation model was used to explore how precipitation affects the livestock DSB by quantifying changes in the AGV in the basin. The results showed that horses [seedling density 5.32 (2018), 6.30 (2019) and 7.44 (2020) g−1 dung] had greater seed dispersal potential than cattle (3.91, 5.08 and 6.42 g−1 dung) or sheep (0.88, 1.32 and 2.96 g−1 dung), indicating that horse dung contributes the most to the AGV in the Qaidam basin. Furthermore, the seed composition of the DSB differed substantially from species of the AGV, implying that the DSB can promote the diversification of grasslands. An increase in precipitation increased both the productivity of the AGV (and hence livestock forage) and the size and composition of the DSB. These results highlight that the DSB is an essential driver of the development of grasslands in arid areas and that the indirect effect of precipitation on the livestock DSB for the regeneration and conservation of grasslands should be considered in arid regions.

Impact of crop rotation with chemical and organic fertilization on weed seed density, species diversity, and community structure after 13 years

We presumed that ecological engineering approaches such as pulse crop inclusion in crop rotation and integrated nutrient management (INM) would have higher weed seed density and diversity compared with continuous cereal-cereal rotation and chemical fertilization in long–run. Hence, we investigated the viable weed seed density and diversity in soil using the seedling emergence method in 0–7.5, 7.5–15, and 0–15 cm depth. Soil sampling was performed in 2016 after 13 years of field experimentation with same treatment combinations and layout on a sandy loam soil of Kanpur, India. The field experiment consisted of four crop rotations (since 2003): rice (Oryza sativa L.)–wheat (Triticum aestivum L.) (R–W), rice–wheat–mungbean [Vigna radiata (L.) R. Wilczek] (R–W–Mb), rice–wheat–rice–chickpea (Cicer arietinum L.) (two years rotation: R–W–R–C), rice–chickpea (R–C) and three nutrient management: control (without fertilization: CT), integrated nutrient management (INM), and recommended inorganic fertilization (RDF). Of the total 30 emerged weed species, 21 species were broad–leaved (70%), 8 grasses (26.7%), and 1 sedge (3.3%). Seed density of Leptochloa chinensis (L.) Nees was significantly higher in R–C(RDF) than R–W–Mb(RDF) and R–W(RDF). While, Lepidium didymum L., Dactyloctenium aegyptium (L.) Willd. and Anagallis arvensis L. were higher in R–W–Mb rotation over the R–W (P < 0.05). Pulse based cropping resulted in 6.1–13.2% higher (P < 0.05) seed density over R–W rotation at 0–7.5 cm depth, while, R–W rotation attributed 2.5–4.9% higher (P < 0.05) seed density than those of remaining rotations at 7.5–15 cm depth. In total depth (0–15 cm), total viable seed density followed the order of R–C = R–W–Mb (P > 0.05) > R–W–R–C (P < 0.05) > R–W (P < 0.05) and INM > RDF > CT (P < 0.05). Importance value index (IVI) of Cyperus rotundus L. and Medicago polymorpha L. was higher for R–W rotation than R–W–Mb, R–W–R–C and R–C (P < 0.05). Notably, pulse based cropping (R–W–Mb and R–C) had the lower ecological dominance and higher Shannon, Simpson, and richness indices than the R–W rotation at 0–7.5 cm and 0–15 cm layer, because of higher species diversity. RDF contained 31% higher ecological dominance than in the INM practice (P < 0.05). Principal component analysis showed that crop rotations and nutrient management mainly influenced the M. polymorpha, D. aegyptium, L. chinensis and L. didymum after 13 years. Medicago polymorpha came out as strongly associated with R–W(INM), while, Spergula arvensis L. and Ammannia baccifera L. emerged as characteristic species in R–C rotation. Thus, it is implied that pulse based cropping and INM could enhance weed seed density with higher species diversity compared with the R–W rotation and RDF in long-run.

Which factors influence the density of birch (Betula pendula Roth) seeds in soil seed banks in temperate woodlands?

The natural regeneration of disturbed forest sites is becoming increasingly important due to climate change. Following disturbance events affecting large areas seed trees are often absent from the site, and regeneration solely by means of seed rain may not be successful. In these situations, soil seed banks are an important driver of the regeneration and reforestation of forest sites. The aim of the study was to determine the birch seed density in the soil of birch stands, spruce–birch stands and spruce stands dependent upon the number of seed trees (stands) and upon varying degrees of ground cover using the ‘seedling emergence method.’ The study revealed a significant link between the quantity of germinated birch seedlings in soil samples and the presence of seed sources. Seedling densities of birch in the different stand categories reached 2644–6414 seedlings per m2 [n m−2] in birch stands, 392–759 n m−2 in spruce–birch stands and 25–122 n m−2 in pure spruce stands. The density of germinated birch seedlings was also negatively affected by the soil layer. In all stand types, the factors humus thickness, litter cover, moss cover and herb cover had no significant influence on the amount of birch seedlings. Successful rapid regeneration of disturbed sites by means of the birch soil seed bank is guaranteed in cases where birch stands, or at least birch seed trees, were present before the event. The influence of ground cover on the regeneration potential of birch from the soil is negligible.

Influence of Short-term Maize–Green Manure Cover Crop Rotations on Germinable Weed Seed Bank under Conservation Agriculture

The effects of one- and two-year maize-cover crop rotations on weed seed bank density and species composition were evaluated in fields at the University of Zimbabwe (UZ) and the International Maize and Wheat Improvement Center (CIMMYT, Harare) between 2014 and 2017. Nine cover crops were rotated, and maize and weed seed bank analyses were done using the seedling emergence method. Maize was used as the control. The results indicated that weed seed density was not significantly (p &gt; 0.05) affected by cover crop mulch type across the seasons. There was a significant (p &lt; 0.05) decline in weed density in the second maize phase of the rotation in UZ Field A. Bidens pilosa, Galinsoga parviflora, Amaranthus hybridus and Eleusine indica were the dominant weeds. B. pilosa density significantly decreased in the second season in UZ Field A but did not vary significantly among cover crops. Significant changes in weed species richness, evenness, and diversity were observed only in the second phase of the rotation in UZ Field A. The results suggest that maize-cover crop rotations could be effective in reducing seed bank size in the short term but have no short-term effect on weed species community composition.

Spatiotemporal characteristics and restoration potentiality of seed banks of aquatic plants in Dabokou wetland in Lake Dianchi, southwest China

以滇池典型生态修复区——大泊口水域为研究对象，研究了富营养化高原湖泊种子库时空特征、种子库与地表覆盖水生植被及水环境的相关关系和恢复潜力.利用高密度样方原位观测与温室控制种子萌发实验相结合，基于2014-2016共3年的长期定位研究，分析湖泊平均种子库密度、分布格局及与覆盖水生植物Sørensen相似性关系，结果显示：年平均种子库形成率在20.35%~34.13%之间，种子库密度2014年为546.67粒/m²，2015年为826粒/m²，2016年为1682粒/m²，眼子菜科的篦齿眼子菜（Potamogeton pectinatus L.）、金鱼藻科的金鱼藻（Ceratophyllum demersum L.）等耐污种属对种子库构成和年增长率贡献较大；垂直方向上种子主要分布于深层底泥（5~30 cm）.随着在时间尺度上的延长，种子库分布更为广泛，且规模越来越大（其中500粒/m²以上规模的分布频率显示增多）.离散系数（V/m）与Lloyd平均拥挤指数（m^*）分析显示主要优势群丛（篦齿眼子菜等）为聚集分布，其余为均匀空间分布格局；种子库与水生植被关系评价指标Sørensen相似性系数（SC）研究显示，滇池大泊口平均SC=（0.3628±0.0265），在湖泊湿地类型和草本群落植被类型属性上处于较低水平，即显示目前植物群落演替过程发生较快，耐污先锋种属在恢复进程上占据优势生态位，而历史优势种和对水环境要求较高的物种却未能规模萌发，一定程度上揭示了高原富营养化湖泊种子库中历史优势植被可恢复性的特征及难点.;Based on long-term dynamics and recent in situ observations across three consecutive years, combined with soil seed samples and greenhouse controlled seedling-emergence methods, this study comprehensively analyzed the scale heterogeneity and spatial-temporal characteristics of seed banks under eutrophic and damaged ecosystems in Dabokou wetland, Lake Dianchi. Seventy-five soil cores were collected from sampling sites within the water area. The sites were systematically distributed using the line-transect method. Investigations were completed a total of 3 times from 2014 to 2016. Species-area relationships were then modeled for pattern detection using seed banks density and characteristics; variance/mean ratio (V/m); and Lloyd's index of mean crowding(m^*). Relationships between seed banks and extant vegetation were also evaluated using Sørensen similarity coefficient(SC). Results showed that the seed density increased significantly accounting for 27.24%. Across the three year period, the mean seed bank densities were:546.67 ind./m², 826 ind./m² and 1682 ind./m², respectively for 2014, 2015 and 2016. Additionally, seven species were detected from seed banks, and most of them were distributed in the deeper bottom sludge as compared to the topsoil(0-5 cm). Over the course of time, there were more and more seed banks dispersal and large-scale density amounting to a distribution frequency of 500 ind./m². The seed pattern of Potamogeton pectinatus L. was aggregated while other extant vegetation was evenly distributed as indicated by aforesaid indices of pattern detection. The mean Sørensen similarity coefficient of Dabokou wetland was 0.3628, a low value for a lake wetland and herbosa-ecosystem. Overall, the succession of aquatic plant communities occurred intensely at Lake Dianchi.

Effects of soil and crop management practices and pedo‐hydrological conditions on the seedbank size of Galinsoga spp. in organic vegetable fields

AbstractGalinsoga quadriradiata and Galinsoga parviflora are very troublesome weeds in many organic vegetable crops in Europe. A very straightforward method to keep Galinsoga infestations under control is by targeting the Galinsoga seedbank. To identify cropping systems able to reduce the seedbank size in vegetable‐based cropping systems, the relationships between the seedbank size of Galinsoga species and prevailing soil/crop management practices and pedo‐hydrological conditions were investigated. Hereto, the seedbank of the 0–20 cm topsoil layer was sampled in 50 organic vegetable fields and analysed according to the seedling emergence method. Field history data were collected for the past 5 years, and physical, chemical and microbial soil quality was determined. Galinsoga quadriradiata was the most frequent and abundant Galinsoga species in the weed seedbank. The genus Galinsoga was present in 90% of the soil weed seedbanks of organic vegetable fields but displayed wide variation in abundance. Smallest Galinsoga seedbanks were found in fields that were predominantly tilled with non‐inversion implements or rotationally ploughed, and continuously cropped with competitive crops during the entire growing season (April 15‐November 15). Contrary to G. quadriradiata, seedbank size of G. parviflora was closely related to soil organic carbon content and sand fraction. Remarkably, soils with a low level of easily plant‐available phosphorus and concomitant high activity of arbuscular mycorrhizae had smaller G. quadriradiata seedbanks. To reduce Galinsoga infestations, fields should preferably be tilled without soil inversion, fertilised with organic amendments with low content of readily plant‐available phosphorus and cropped with competitive crops all season long.

A comparison between reclamation stockpile and boreal forest seed banks and plant communities

Soil stockpiles are essential to the reclamation of large‐ and small‐scale mining and other industrial sites. However, stockpiling soils can lead to the degradation of seed banks. This study examines the diversity, composition, depth of seed storage, and relationships between the aboveground and seed bank plant communities in stockpiles and compares them to the nearby boreal forest. The seed bank and aboveground vegetation sampled at eight stockpiles and six mature forest sites were near Fort McMurray (57.337°N, 111.755°W) and Cold Lake (54.695°N, 110.730°W), Alberta, Canada. Seed bank samples were taken from the forest floor (LFH) and depths of 0–5, 5–10, 10–20, 20–30, &gt;50 cm. Aboveground vegetation cover was also estimated at these locations. The seed bank composition was determined using the seedling emergence method in a greenhouse. Stockpile seed banks had higher seedling abundance and species richness than nearby forested sites but were dominated by grasses and non‐native forbs. Most seeds germinated from the surface layer, with 92% of seeds germinating from the LFH layers in the forested sites, and 68% from the 0 to 5 cm layer in the stockpiles. Mature forest sites had more similar aboveground and seed bank communities than the stockpiles. Overall, integrating information on seed bank and aboveground plant communities would improve reclamation decisions, rather than relying on aboveground vegetation alone.

How Does the Engineering Species Affect Forest Ecosystems? Changes in Germination and Development Rate of Non-Forest Species Under the Nests of Ardea cinerea L.

Abstract An ecosystem engineer is a species that indirectly changes the availability of resources for other organisms via physical modification of the habitat. A good example of such species is Ardea cinerea L. – a big waterbird that forms colonies up to a few hundreds of nests during the breeding season. The colonies modify the habitat in the close vicinity of the nests mainly through heavy input of organic matter (feces, dropped or regurgitated food leftovers, eggshells, dead birds, etc.), which in turn affects vegetation. In our previous study, we observed that the probability of occurrence of non-forest species under the nests was 29.5 times higher in control plots in two types of forest vegetation (oligotrophic pine forest and riparian mixed forest). Adaptation for long-distance dispersal turned out to be insignificant for the probability of species occurrence, which suggested that the diaspores of those species must have been present in the forest soil before the establishment of the grey heron colony. In the present study, we used the seedling emergence method to compare the structure of the soil seed bank in breeding sites and control plots in two forest ecosystems mentioned above. We also tested whether the increased amount of nitrates in soil had a positive effect on the rate of germination and growth of seedlings. The results have shown that some reservoir of ruderal species was indeed present in the control plots, although their amount was higher under the heronries. We have proved that the number of germinating seeds of ruderal species depends on the concentration of nitrate in the soil of the pine forest. Comparison of the dry weight of 30- and 60-day-old seedlings of Rumex acetosella (pine forest) and Betula pendula (riparian forest) from the control and breeding sites showed an increased size of seedlings coming from the breeding sites of both forest communities.

Improvement of the seedling emergence method in soil seed bank studies using chemical treatments

The seedling emergence method (SEM) is the most frequently used method for studying the soil seed bank. The main problem with this method is that it cannot provide a complete assessment of the seed flora present in the soil because its results are influenced by seed dormancy. In order to break seed dormancy of the soil seed bank, SEM can be combined with some chemical treatments. The objectives of this study were to determine the best chemical treatment which is able to overcome seed dormancy, and to study the effects of different chemical treatments on soil seedling emergence of different plant functional groups. Therefore, twenty soil samples were collected in the early spring in subalpine rangelands in northern Iran. Each soil sample was divided into four equal subsamples, and each subsample was treated by one of the dormancy-breaking treatments including gibberellic acid (GA3), hydrogen peroxide (H2O2), potassium nitrate (KNO3) and distilled water as control. The emergent species from the soil samples were categorized into functional groups, i.e., annual forbs, perennial forbs and perennial grasses. The results showed that the highest total seedling emergence was observed in the soil samples treated with GA3 (5465 seedlings/m2), whereas the lowest seedling emergence was found in the soil samples by KNO3 application (586 seedlings/m2). The perennial forbs were the only functional group that responded to all chemical treatments. We concluded that the use of GA3 for breaking seed dormancy can be useful for providing a more reliable estimation of the soil seed bank characteristics.

Variabilidade espacial do banco de sementes em área de Caatinga no Nordeste do Brasil

O banco de sementes no solo é uma das principais estratégias de sobrevivência em longo prazo das comunidades vegetais diante da sazonalidade e da irregularidade do regime pluviométrico em áreas áridas e semiáridas. Considerando a forte variação na riqueza e a densidade do banco de sementes nesses ambientes, este estudo tem como objetivo avaliar a variação espacial do banco de sementes em uma área de Caatinga, no Nordeste do Brasil, determinando a sua composição florística e densidade de germinação. A área selecionada foi uma lagoa temporária no Cariri paraibano, com vegetação altamente antropizada, devido a diversos usos ao longo do tempo. Em cada ponto cardeal, tomando como referência o centro da lagoa, foram retiradas amostras de solo para o banco de sementes. Todo o material coletado foi distribuído em bandejas plásticas e irrigado diariamente. A determinação da densidade de sementes no banco do solo foi realizada pelo método de emergência de plântulas e expressa em sementes.m-². A flora do banco de sementes do solo da Caatinga foi representada neste estudo por 26 espécies e três morfoespécies, distribuídas em 11 famílias e 26 gêneros, dentre elas as famílias Poaceae e Asteraceae, com maior número de espécies. A principal forma de vida do banco de sementes foi herbácea e a densidade média da área de estudo foi de 2.942 sementes.m-2 (lagoa) e 3.826 sementes.m-2 (no entorno) e após o estresse hídrico foi de 732 sementes.m-2 e 1.208 sementes.m-2, nas áreas da lagoa e do seu entorno, respectivamente. A área do entorno da lagoa apresenta a maior densidade de plantas por m² e maior diversidade de espécies. Além disso, o sentido Norte, em ambas as áreas, apresentou menor densidade de sementes.m-².

Soil seed bank in a subtropical grassland under different grazing intensities

ABSTRACT Grazing is an important determinant for the composition and structure of grasslands; however, soil seed bank (SSB) response to grazing intensity is poorly investigated. We analyzed SSB richness and density in a subtropical grassland in southern Brazil with different forage offers (low, intermediate, high and very high), that is, contrasting grazing intensities. The SSB was evaluated by the seedling emergence method. We collected ten SSB samples at two layers (0-5 and 5-10 cm) in spring and autumn in each of grazing intensity treatments. We surveyed the established vegetation to assess its similarity with the SSB. Treatment effects were analyzed by Poisson regression while compositional differences were visualized by ordination. We found 103 species in the SSB, of which 71 were also found in established vegetation. We found a positive correlation between SSB density and grazing intensity. High grazing intensity influences patterns of composition and dominance in the SSB, while no strong differences were found among the other treatments. The SSB was characterized by low participation of dominant grasses in the vegetation and the dominance of ruderal species, indicating that recovery from the SSB after total removal of vegetation (severe disturbance) may be limited in grasslands in the region.

Banco de sementes em reflorestamento, borda e interior de remanescente de floresta estacional semidecidual no sul do Brasil

In order to compare the composition of the seed bank in the seasonal semi-deciduous forest remnant and in the adjacent reforestation, 60 soil samples were collected in four transects allocated in the forest interior (TIF), forest edge (TBF), reforestation edge (TBR) and reforestation interior (TIR). These samples were kept in greenhouse and monitored for eight months. The seed bank was registered according to the seedling emergence method. TIF presented the greatest richness of trees, while in the other transects there was a predominance of herbaceous and anemochorous species. We observed the occurrence of exotic species in the bank. The low richness of tree species in the reforestation seed bank, despite its proximity to a conserved fragment, suggests that management actions should be evaluated and implemented in order to accelerate the successional process.

Kelimpahan Vegetasi dan Simpanan Biji Gulma pada Pertanaman Jagung Berbeda Sejarah Pola Tanam di Lahan Kering

Weed management is an important aspect in the dry land; however, weed resides in dry land like East Nusa Tenggara is rarely reported. The study aimed to evaluate weed species and its seed bank on maize fields from the different history of cropping patterns in order to develop effective weed control. The research was conducted in April-June 2019 at farmer fields at Kupang District, East Nusa Tenggara, Indonesia. Weeds were evaluated from four maize fields experienced a different history of cropping pattern (L1, L2, L3, and L4), and its seed bank from the depth of 0-10, 11-20, 21-30, and 31-40 cm were evaluated using seedling emergence method. The evaluation revealed 13 species at which 4 species exclusively were found in vegetation analysis, 2 species in the seed bank and 7 species in both vegetation and seed bank analysis. Dominant weed at podzolic L2 and L3 that experienced fallow for two months was Chloris barbata, while without fallow of podzolic L1 and grumusol L4 were Digitaria adscendens and Mazus japonicus, respectively. Cropping history and soil depths affected weed density, but depths of 0-20 cm had the highest density irrespective preceding the cropping pattern. Research implies both vegetation and seed bank analysis should be addressed and integrated in weed management.&#x0D; Keywords: dry land, fallow, weed management, East Nusa Tenggara, vegetation analysis