Seed Bank Density Research Articles

Global patterns of potential future plant diversity hidden in soil seed banks

Soil seed banks represent a critical but hidden stock for potential future plant diversity on Earth. Here we compiled and analyzed a global dataset consisting of 15,698 records of species diversity and density for soil seed banks in natural plant communities worldwide to quantify their environmental determinants and global patterns. Random forest models showed that absolute latitude was an important predictor for diversity of soil seed banks. Further, climate and soil were the major determinants of seed bank diversity, while net primary productivity and soil characteristics were the main predictors of seed bank density. Moreover, global mapping revealed clear spatial patterns for soil seed banks worldwide; for instance, low densities may render currently species-rich low latitude biomes (such as tropical rain-forests) less resilient to major disturbances. Our assessment provides quantitative evidence of how environmental conditions shape the distribution of soil seed banks, which enables a more accurate prediction of the resilience and vulnerabilities of plant communities and biomes under global changes.

The feasibility of using soil seed bank for natural regeneration of degraded sandy grasslands

Desertification in degraded grasslands is manifested through the development of bare sandy patches, which eventually lead to habitat fragmentation. The ability of these bare sandy patches to regenerate naturally through in-situ soil seed banks is not well understood. To fill this knowledge gap, we randomly selected 24 bare sandy patches with areas ranging from 19 to 898 m2 in a desertified grassland of the Horqin sandy land, Northern China to determine whether soil seed bank can be used for natural regeneration of bare sandy patches. Species composition and density of soil seed bank as well as aboveground vegetation composition, abundance and coverage were investigated. We then determined their relationships with in-situ habitat characteristics. Our observations showed that the studied area had low soil seed bank density and species richness, as well as depauperate soil seed bank communities. Consequently, local soil seed bank was not able to provide sufficient seed source for natural regeneration. This was indicated by the relationships between aboveground vegetation, soil seed bank and the in-situ habitat characteristics. For bare patches with an area between 300 m2 and 900 m2, increase the soil seed bank density and species richness should be the main restoration measures. For bare patches with a small area of less than 50 m2, restoration of vegetation density should be the main measure. Our data highlighted that different extents of desertification, indicated by different bare patches, are requiring distinct restoration measures.

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

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

Do common assumptions about the wetland seed bank following invasive plant removal hold true? Divergent outcomes following multi‐year Phragmites australis management

AbstractQuestionLimited funds and compressed timelines frequently translate into a reliance on seed banks for native plant recovery following invasive plant management. This approach assumes: (a) baseline seed bank communities are sufficient for native plant recovery regardless of site environmental conditions; (b) different management actions variably impact native and invader seed banks; (c) management actions reduce invader seed banks; while (d) native seed banks do not decline following management; and (e) returning above‐ground vegetation reflects the seed bank. Do these assumptions hold true in the context of invasive Phragmites australis management?LocationGreat Salt Lake wetlands, Utah, USA.MethodsAcross six sites, we applied six Phragmites management treatments (solarization, or glyphosate or imazapyr herbicide in the summer or fall with mowing) for three years, and monitored two more. Each year, we assessed the above‐ground vegetation and seed bank using the seedling emergence method.ResultsSite environmental conditions drove baseline seed bank communities: seed banks differed substantially across sites with varying anthropogenic degradation as less disturbed sites had greater seed bank richness. Different management actions had similar impacts on native and invader seed banks. Phragmites seed density was reduced after herbicide treatments while native seed bank communities were unaffected. Above‐ground vegetation generally reflected seed bank communities. However, native graminoids were present in seed banks but surprisingly rare above‐ground.ConclusionCommonly held assumptions about invasive plant management and native recovery from the seed bank did not all hold true. Native seed banks were particularly insufficient for recovery at sites with greater degradation, suggesting managers should prioritize management at less degraded sites or consider revegetation in highly degraded sites. Despite reductions in Phragmites seed bank density, Phragmites propagule pressure remained high, requiring a long‐term management commitment. Often seed banks are insufficient and revegetation of desired above‐ground species is necessary to meet restoration goals.

Seasonal Dynamics in Forest Soil Seed Banks along an Elevational Gradient in the Rocky Mountainous Area of North China

Although exploring soil seed bank characteristics and dynamics is conducive to plant diversity protection and restoration, few investigations have been undertaken in the rocky mountainous area of North China. To address this research gap, qualitative and quantitative changes in soil seed bank characteristics over different seasons and elevations as well as potential causes for differences were examined, using data from 25 secondary forest communities in the Songshan area of Beijing, China. Nonmetric multidimensional scaling (NMDS) was used to test the similarity of the composition of the seed bank and the understory vegetation during different seasons. In addition, the structural equation model (SEM) was used to explore the direct and indirect effects on seed bank density. The results indicate that abundance and species richness decreased with elevation, with seed density reaching its maximum and minimum levels in April and July at all elevation levels, respectively. In terms of species composition, the understory vegetation was significantly different from the seed bank, and the proportion of herbaceous plants species in the seed bank was higher. Soil total nitrogen, available phosphorus and available potassium all changed with elevation, directly or indirectly affecting seed bank density. The application of seed banks present in topsoil from the rocky mountainous area of North China can be potentially used for ecological restoration. It is important, however, to consider the elevation and the season related to the removal of the topsoil to achieve optimal effects.

The Similarity between Species Composition of Vegetation and Soil Seed Bank of Grasslands in Inner Mongolia, China: Implications for the Asymmetric Response to Precipitation.

The asymmetric response of productivity to precipitation was recently proposed as an early warning signal for the shifts in temperate grassland function in China. It was hypothesized that the asymmetry was influenced by the increased growth of the newly emerged seedlings from the soil seed bank. Therefore, the seed density in the soil seed bank and the similarity between species composition of the vegetation and the soil seed bank should be maximized where asymmetry was maximized. However, this knowledge was still limited and unconfirmed. In this study, the desert steppe, typical steppe and the transition zone between them (with the highest asymmetry) were selected for studying the similarity index in both 2018 (dry year) and 2019 (wet year). Plant species composition was monitored in situ using an unmanned aerial vehicle. Soil seed bank samples were collected, and the seed bank density and species composition were then examined and identified in the laboratory. Results showed that: (1) The variation in vegetation species richness between the two years was the highest (41%) in the transition zone (p < 0.05), while it was only 7% and 13% for the desert steppe and typical steppe, respectively. The presence of herbaceous species mainly caused the differences in variation among three grassland types. (2) Seed density was the highest in the transition zone (114 seeds/m2 and 68 seeds/m2 in the transient and persistent soil seed bank, respectively) (p < 0.05). Additionally, herbaceous species were the main components of the soil seed bank. (3) The similarity index was the highest in the transition zone (p < 0.05), with 38%/44% and 33%/44% for the transient/persistent soil seed bank in 2018 and 2019, respectively. Our study demonstrated that variation in vegetation species composition was very similar to the composition of the seeds accumulated in the soil seed bank. These results warrant further investigation for the mechanism of asymmetric response of productivity to precipitation.

Extreme drought has limited effects on soil seed bank composition in desert grasslands

AbstractQuestionDoes climate change affect vegetation and seed bank composition in desert grasslands?LocationSevilleta National Wildlife Refuge, New Mexico, USA.MethodsVegetation and seed bank species composition were recorded in black grama (Bouteloua eriopoda) and blue grama (Bouteloua gracilis) grasslands. At each site, two rainfall manipulations and ambient controls were established in 2013 (n = 10). Treatments included extreme drought (−66% rainfall reduction during the growing season) and delayed monsoon (precipitation captured during July–August and reapplied in September–October). Above‐ground species composition was assessed, and composite soil samples were collected in 2017, five years after the experiment started. Seed bank was evaluated using the seedling emergence method.ResultsRainfall treatments increased the above‐ground vegetation and seed bank richness in the blue grama community, but not in the black grama community. Vegetation cover was reduced by both rainfall manipulations, but seed bank density increased or remained the same compared with controls. In above‐ground vegetation, cover of annual and perennial forbs increased, and dominant perennial grasses decreased under drought. In the soil seed bank, species composition was similar among all treatments and was dominated by annual and perennial forbs.ConclusionsThe seed bank was more resistant to drought than above‐ground vegetation. Because seed banks can enhance long‐term community stability, their drought resistance plays an important role in maintaining ecosystem processes during and following drought in these grassland communities.

Forest degradation and short-term seasonal exclosure effects on biotic and abiotic factors linked to rangeland rehabilitation in semiarid Chaco, Argentina

In semiarid Chaco, wet season grazing exclosures allow a rapid grass recovery in mature and secondary forest patches, but not in the most degraded patches dominated by shrublands. In order to understand the causes of their dissimilar rehabilitation dynamics, we analyzed the effects of the forest-patch type (mature forest = MF, secondary forest = SF, and shrubland = S) and 4-year seasonal exclosures (vs continuous grazing) on biotic and abiotic factors (vegetation structure, incident radiation, grass seed bank, litter and soil traits) that could affect grass recovery. We found that vegetation structure, through determining litter quantity, controlled soil chemical traits. As forest degradation level increased, litter mass (MF = 6260, SF = 5410, S = 1220 kg DM/ha), total soil organic matter (MF = 5.1%, SF = 4.1%, S = 3.5%) and nitrogen (MF = 0.25%, SF = 0.22%, S = 0.18%) decreased, and the incident radiation at soil level rose (MF = 28%, SF = 41%, S = 52%). After 4 years of seasonal grazing rest, we found reduced soil bulk density (from 1.13 to 1.07 and 1.07 to 1 g/cm3) and increased total porosity (from 57 to 60 and 60 to 62%) at 0–10 and 10–30 cm depth, respectively, in all forest patch types. Exclosure also increased soil seed bank density (from 28 to 251 grass seeds/m2) both in the forests (with grass) and in the shrublands (even before grass recovery), which would receive seeds from the adjacent forest patches, which coexist in the same landscape matrix. Our results suggest that the low tree cover, litter, and soil chemical traits related to lower availability of water and nutrient in shrublands, could hamper grass recovery in recently established exclosures. However, improvements in the grass seed bank and soil physical traits related to higher water infiltration could favor its late recovery, which is triggered by an extremely wet cycle after several years of the seasonal exclosure. Exclosure is a promising management strategy for degraded areas involving intermingled patches of forests and shrublands.

Composition of native and alien invasive species in soil seed banks of five different physiognomies in Akure Forest Reserve, Ondo State, Nigeria

The study investigated the composition of native and alien invasive species in soil seed banks of five different vegetation physiognomies in Akure Forest Reserve Ondo State, Nigeria. This was done with a view to determining and providing an insight into the population dynamics of alien, invasive species for subsequent prediction of potential plant population of the extant population. Five distinct sites (Natural forest, Teak plantation, Taungya system, Taungya + Teak + Gmelina and Teak + Gmelina + Pinus Plantation) designated as A, B, C, D and E were selected in the Forest Reserve. Two plots 25 m x 25 m each were selected for sampling in each of the five distinct physiognomies. Five replicates soil samples were randomly collected at 0-15 cm soil depth in dry and rainy seasons in each site and they were subjected to seedlings emergence for six months to determine the density and species composition (natives or aliens and percentage contribution) of the seed bank. The results of the seedling emergence revealed that the seed bank was dominated by herbaceous stems and also the proportion of aliens to natives was low. Analysis of variance revealed that there was no significant difference (P&gt;0.05) in the density of both the aliens and native species in sites A, B and C indicating similarities in the seed bank density of the aliens and natives in the three sites while in sites D and E, there was a significant difference (P&lt;0.05) indicating dissimilarity in the seed bank density of the aliens and natives in the two sites.Keywords: Plant Ecology, Forest, Seedling Emergence, Seed Bank, Alien Species, Conservation.

Rice Paddy Soil Seedbanks Composition in a Mediterranean Wetland and the Influence of Winter Flooding

Soil seedbanks are defined in composition and quantity by many environmental factors inherent to a specific area, and they can be an indicator of the potential problems of weeds in crops. In Valencia (Spain), rice is cultivated with continuous flooding during the growing season, and after harvesting, many of the paddy fields are flooded again during the winter. This study investigates the paddy fields’ soil seedbank composition in this Mediterranean paddy area and the effect of winter flooding on the soil seedbank. Multispectral images from the Sentinel-2 satellite were used to characterise the water level of paddies in winter. Satellite images facilitated the characterisation of winter flooding in fields. Soil samples from sixty-nine points distributed over 15,000 ha of paddies were used to determine the composition of the seedbank plots. The data were spatially represented by geographic information systems. The species that contributed most to the paddy seedbank were Cyperus difformis L., an important rice weed in the Mediterranean area, and other rice weeds such as Echinochloa sp. and Leptochloa fusca subspecies. Other species with a great contribution to the seedbank are species that develop in paddy fields that produce a large quantity of small seeds, such as Lemna sp., Polypogon monspeliensis (L.) Desf., and Nasturtium officinale R. Br. These species interfere little or do not interfere with the rice crop. The study revealed that in general, flooding reduced seedbank density with differences between species. Furthermore, the influence of winter flooding on the different plant species obtained as well as their distribution maps are a further step in this protected area from the point of view of weed management in rice crop, as well as in the management of this Mediterranean wetland.

Evaluation of Soil Physicochemical Properties, Soil Seed Bank and Species Density of Five Plant Communities in Awka Anambra State

The research study investigated the physicochemical properties of the soil in five different locations around Nnamdi Azikiwe University Awka campus for their above ground and seed bank status with regards to their germination rate and species density. The study areas were located at Cattle grazed field at gariki Amansea, abandoned farmland near Chisco Transportation and Engineering workshop, frequently mowed lawn at Unizik e-library, a Savanna woodland behind the banking plaza Unizik and tropical lowland forest at Botanical garden Unizik. The seed bank investigation was conducted from September 2016 to March, 2017. Analysis of variance was used to test significant differences between seed bank densities among experimental plots at different soil horizons. The soil physiochemical parameters among the experimental plots were also analyzed by one-way analysis of variance. Significant differences were tested at P= 0.05 at 95% confidence intervals. Results revealed the highest value for above ground species was found in tropical lowland forest (53.67±6.11) while the lowest was in cattle grazed field (8.00±0.82). Meanwhile the highest value for seed bank was in the frequently mowed lawn Unizik e-library (93.00±18.00) and the lowest was in the forest (6.50±4.95). The comparison of the two groups using T-test revealed that there was a significant difference between the above ground and seed bank values of the tropical lowland forest P=0.003 and also between the above ground and seed bank values of the frequently moved lawn, Unzik e-library P=0.001. More so, the Savanna above ground values and seed bank species value were not significant at P=0.006, as well as cattle grazed field (8.00 ± 0.82) and (50.00± 19.31) at P=0.006. Also, the Savanna plot comparison of above ground (44.50±3.54) and the seed bank (14.00±5.20) revealed significant differences between the two groups at P=0.006. Electrical conductivity was highest in the cattle grazed field (40.00+1.08) and the highest pH value was found in the Unizik e-library (6.19+0.22). Sorensen’s coefficient index revealed the highest similarity between above ground and seed bank species occurred in the cattle-grazed field followed by the frequently mowed lawn Unizik e-library (0.196), then the abandoned farmland (0.074), the Savanna (0.060) and the forest (0.025) respectively. Since the similarity is measured between 0 and 1, it means therefore that there is a weak similarity (0.276) between above ground vegetation and the seed bank in the cattle grazed field while the frequently mowed lawn (0.196) above ground similarity with seed bank was very weak. There is no similarity (0.025) between the above ground vegetation and the seed bank in the tropical forest. This seed bank investigation showed that the number of plant species in the seed bank does not reflect the total number of species in the above ground and the soil properties have an impact on the species density of the areas.

Long-Term Soil Nutrient Management Affects Taxonomic and Functional Weed Community Composition and Structure

Weed communities can be influenced by nutrient availability, nutrient form (e. g., ammonium vs. nitrate), amendment timing, amendment type (e.g., organic vs. inorganic), and by immigration of seeds during amendment applications. The objective of this research was to compare the long-term effect of different fertility treatments in a corn (Zea mays L.)-alfalfa (Medicago sativa L.) rotation on taxonomic and functional structure and composition of weed communities by analyzing the soil weed seedbank. After 14 years of a long-term experiment in Aurora, NY, United States, soils were sampled in five fertility treatments for corn years in the rotation: liquid dairy manure, semi-composted separated dairy solids; or inorganic nitrogen (N) as starter fertilizer with either no sidedress N, a low rate or a high rate of inorganic N as sidedress fertilizer. Soil was collected in early spring 2015 and a greenhouse weed seed germination bioassay was used to quantify the germinable soil weed seedbank. Total weed seedbank density, species richness, and evenness did not vary by treatment. However, fertility treatments modified the ecological niche represented by 20 environmental descriptors, which filtered the weed community creating distinct functional group assemblages. A trait-based analysis revealed that nitrophilic dicotyledons preferring alkaline soil were associated with high concentrations of inorganic N fertilizer, whereas highly specialist monocotyledons preferring high amounts of light were associated with low concentrations of inorganic N fertilizer. Because fertility treatments affected weed community composition but not seed bank density and richness, results encourage the development of holistic management strategies that adopt coherent weed management and crop fertilization.

Seed bank persistence of a South American cordgrass in invaded northern Atlantic and Pacific Coast estuaries.

Invasive alien plant species impart considerable impacts that contribute to the decline of biodiversity worldwide. The ability of an invasive species to overcome barriers to establish and spread in new environments, and the long-term effects of plant invasions supporting their persistence are keys to invasion success. The capacity of introduced species to form soil seed banks can contribute to their invasiveness, yet few studies of invaders have addressed seed bank dynamics. Improved knowledge of this recruitment process can improve conservation management. We studied temporal and spatial changes in soil seed bank characteristics of the cordgrass Spartina densiflora from two continental invaded ranges. In the Odiel Marshes (Southwest Iberian Peninsula), S. densiflora formed transient seed banks (<1 year). At Humboldt Bay Estuary (California), viable seeds persisted for at least 4 years though the germination percentage fell abruptly after the first year from 29 % to less than 5 % of remaining viable seeds. Total soil seed bank density increased with S. densiflora above-ground cover in both estuaries, pointing to the transient component of the seed bank as a critical component of vegetation dynamics during S. densiflora invasion. Even so, seed densities as high as c. 750 seeds m-2 in Odiel Marshes and c. 12 400 seeds m-2 in Humboldt Bay were recorded in some plots without fruiting S. densiflora plants. S. densiflora spikelet (dispersal unit) density was more than double close to the sediment surface than deeper within soil. Our study shows the importance of evaluating seed banks during the design of invasive species management since seed bank persistence may vary among invaded sites, and can affect the timing and duration required for desired management outcomes.

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 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 &gt;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.

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.

The effects of land use and microsite availability on early seedling recruitment of Acacia tortilis (synonym: Vachelia tortilis) in a southern African savanna

Many tree recruitment studies in African savannas target individual factors that limit recruitment, yet recruitment of some species could be limited by an interplay of environmental filters. This study investigated the effects of land use and microsite availability on early seedling recruitment of Acacia tortilis in riverine woodlands in north-western Zimbabwe. The riverine woodlands were divided according to the level of human disturbance into protected and unprotected sites. Each site was further divided into riverine and off riverine microsites. In each microsite, we laid five main plots (100 × 50 m) and nine seedling subplots (5 × 5 m) nested in each main plot, making a total of 60 main plots and 180 subplots. We found higher seedling recruitment in unprotected than protected sites. Although seeder density was twice greater in protected than unprotected sites, seed bank density was lower in the former by a factor of 1.5. Tree cover and herbaceous biomass was 1.4 and 1.8 times greater in protected than unprotected sites, respectively but were negatively correlated with seedling density. Across all microsites, herbivory-related mortality was less than 40% while drought-related mortality was more than 60%. Put together, the results suggest that higher recruitment in unprotected sites was most likely facilitated by domestic ungulates through seed dispersal and grass suppression which enhanced the quality of regeneration sites. We conclude that encroachment of A. tortilis in communal grazing sites is not only important for its conservation but for a variety of goods and services derived from it.

Inferring trait‐based mechanisms and variance consequences of abiotic secondary dispersal from the spatio‐temporal distribution of a desert soil seed bank

AbstractQuestionsQuantifying the combined effects of seed traits, microsite types, and abiotic dispersal agents on the mean and variance of seed bank density and composition will help understand vegetation dynamics in deserts. In a site with NE slope and mainly southerly winds, we asked whether large and oblong seeds were more likely to be transported and deposited in water obstructions and underneath the northern part of shrub understories. We also asked whether seed standing crop was less variable in water obstructions than in other microsites less affected by seed deposition.LocationA sand field in San Juan province, Argentina.MethodsWe sampled the soil seed banks of four microsite types: water obstructions where debris/litter accumulates, southern and northern shrub understories, and open spaces among shrubs. Sampling was carried out in 11 plots and replicated at six moments between 2010 and 2012.ResultsDebris microsites showed the highest levels of seed density, species richness and standing crop; seed density and standing crop were also least variable in these microsites. Debris microsites also contained high seed abundance of stress‐intolerant, shrub‐dependent species. Seed density, species richness, seed standing crop, and the proportions of both large and oblong seeds were all higher in northern than in southern understories. The relationship between seed mass and the proportion of seeds that were apparently retained (i.e., not washed away and deposited in water obstructions) was more strongly negative in southern than in northern understories.ConclusionsNorthern and southern understories appeared to act as water run‐on (i.e., seed recipients) and run‐off zones (i.e., seed donors), respectively. Seed accumulation under the shelter provided by shrubs may promote seed predation in these microsites. Abiotic dispersal would therefore contribute to the maintenance of vegetation patches when seed arrival underneath shrub canopies saturates granivore consumption.

IDENTIFICATION OF LOCAL SEEDS BANK WEED AND THE EFFECT OF WEEDING FREQUENCY ON GROWTH AND RESULTS OF CAYENNE (Capsicum frutescens)

Weed is a plant pest organism whose existence is very detrimental to the production of cultivated plants. Weeds and major plants compete to obtain nutrients, sunlight, and water so that their availability is limited to the main plants. Weed abundance in a cultivated land is inseparable from the presence of weed seed banks in the soil. This study aims to identify weed bank seeds in chili cultivation in Tandon Hamlet, Selogiri Subdistrict, Wonogiri Regency and find out the right weeding frequency to get the highest productivity of cayenne pepper. Identification of local weed bank seed by taking soil samples at four different depths, a) 0-5 cm depth; b) 5-10 cm depth; c) 10-15 cm depth; and d) a depth of 15-20 cm. The variables observed included weed frequency, weed density, and summed dominance ratio (SDR). The frequency of weeding of cayenne plants, using a randomized completely block design (RCBD) with one treatment factor, namely weeding frequency (without weeding; 1 weeding at 2 weeks after planting (MST); 2 times weeding at 2 MST and 4 MST; 3 times weeding at 2 MST, 4 MST, and 6 MST; 4 times weeding at 2 MST, 4 MST, 6 MST, and 8 MST). The results showed that the highest weed seed bank density was found in the depth of soil 0-5 cm and 5-10 cm. While the frequency of weeding shows the frequency of 3 times weeding gives the best results on the growth and production of cayenne

Effects of Long-Term Cover Cropping on Weed Seedbanks

Cool-season cover crops have been shown to reduce soil erosion and nutrient discharge from maize (Zea maysL.) and soybean [Glycine max(L.) Merr.] production systems. However, their effects on long-term weed dynamics are not well-understood. We utilized five long-term research trials in Iowa to quantify germinable weed seedbank densities and compositions after 10+ years of cover cropping treatments. All five trials consisted of zero-tillage maize-soybean rotations managed with and without the inclusion of a yearly winter rye (Secale cerealL.) cover crop. Seedbank sampling was conducted in the early spring before crop planting at all locations, with three of the five trials having grown a soybean crop the preceding year, and two a maize crop. Two of the trials (both previously soybean) showed significant and biologically relevant decreases (4,070 and 927 seeds m−2, respectively) in seedbank densities in cover crop treatments compared to controls. In another two trials, one previously maize and one previously soybean, no difference was detected in seedbank densities. In the fifth trial (previously maize), there was a significant, but biologically unimportant increase of 349 seeds m−2. All five trials' weed communities were dominated by common waterhemp [Amaranthus tuberculatus(Moq.)], and changes in seedbank composition from cover-cropping were driven by changes in this species. Although previous studies have shown that increases in cover crop biomass are strongly correlated with weed suppression, in our study we did not find a relationship between seedbank changes and the mean amount of cover crop biomass produced over a 10-years period (experiment means ranging from 0.5 to 2.0 Mg ha−1yr−1), the stability of the cover crop biomass production, nor the amount produced going into the previous crop's growing season. We conclude that long-term use of a winter rye cover crop in a maize-soybean system has the potential to meaningfully reduce the size of weed seedbanks compared to winter fallows. However, identifying the mechanisms by which this occurs requires further research into processes such as seed predation and seed decay in cover cropped systems.