Species introduction through seeds from an old,species‐rich hay meadow: Effects of management

Abstract. A local seed mixture from plants growing in a species‐rich, traditionally managed hay meadow site at Varaldsoy, Hardanger, western Norway, where many endangered hay meadow species of the region are growing, was sown in a newly harrowed experimental field 1 km from the source meadow in order to increase the habitat area for the endangered species. Of 25 endangered species recorded in the source meadow, only one (Holcus lanatus) was present in the target meadow. After sowing, 16 of the endangered species in addition to Holcus lanatus were recorded in the new site. Six species were only present in sown plots and seven others were more frequent there, while three species might have arrived by chance or originated from the seed bank. Replacing the traditional management regime, including one late cut and grazing in spring and in autumn, with three cutting times and the creation of gaps in the sward, resulted in a higher number of endangered species in plots which were only cut, possibly because the grazing was too intensive in the small enclosures.     

Restoring the Victorian Western (Basalt) Plains grassland. 1. Laboratory trials of viability and germination, and the implications for direct seeding

Summary   The Victorian Western (Basalt) Plains grassland is one of Australia's most threatened plant communities. Practitioners using seed for its restoration need to know whether seed can be sown fresh or whether it requires an after-ripening period. This study assessed the viability and germination of freshly harvested wild seed from 64 grassland species indigenous to the Basalt Plains of western Victoria. The seed was collected as part of a broader experiment that examined the potential of direct-sown complex seed mixes for the restoration of grassland communities. The germination of fresh seed at 25°C varied widely between species. Comparisons with tetrazolium viability tests for each species indicated varying levels of dormancy within the species pool. Germination separated into three broad responses at day 28. One-third of the species failed to germinate, one-third germinated at 1% to 50% and the remaining species germinated between 51% and 100%. Therefore, if the aim of a sowing was the rapid and synchronous establishment of most of the sown species, the use of fresh seed in restoration could be problematic. After 3 months of dry storage, eight species were re-tested for germination. Each of the selected species had shown high viability but low initial germination. Only two species significantly increased their total germination at 25°C. The annual species, Triptilodiscus pygmaeus , increased its total germination from 6% as fresh seed to 99% after dry storage. Testing the viability and germination capacity of freshly harvested seed from a large and diverse sample of native grassland species demonstrated that many of the species were unlikely to germinate rapidly or synchronously when sown in complex seed mixes soon after harvest. This finding has implications for the scheduling and management of restoration projects that rely on the use of such seed.     

Seed size, shape and vertical distribution in the soil: indicators of seed longevity

1. We investigated the vertical distribution of seeds in the soil, using data from nine studies in five European countries. We discovered significant correlations between seed shape and distribution in the soil.
2. The classification of the longevity of seeds of plant species has been improved by the introduction of a 'longevity index', expressing on a continuous scale the most recent information on seed longevity represented as the proportion of non-transient seed bank records in the database of Thompson et al. (1997 ). Remarkably, no difference in seed longevity was found if the index was based on direct observations only when compared with the index based on the complete data set where indirect, 'depth-derived' observations were included.
3. Seed longevity was best estimated using a multiple regression model with an integrated measure of seed size and shape and depth distribution of seeds.
4. The shape of seeds, known to be a consistent character of species, was shown to be constant within species, whereas depth distribution of seeds was highly variable among sites. This is consistent with the variability of seed longevity found in published seed bank data.     

Soil nutrient input effects on seed longevity: a burial experiment with fen-meadow species

1. Effects of high nutrient input on the longevity and viability of buried seed are examined. Seeds of 17 fen-meadow species were buried in nylon mesh bags at four sites in the Netherlands and one site in Great Britain in plots to which N, P, K fertilizers are applied. Prior to burial germination tests were conducted on the seeds of each species. This paper describes the results of the viability tests on the seeds that were exhumed after one and 2 years of burial.
2. The percentage of seeds that germinated after 1 year of burial was significantly lower than the pre-burial percentage for the majority of the species. After 2 years of burial the germination percentage further decreased. A few species, such as the Carex species, did, however, show an increase in germination percentage indicating that the burial conditions allowed dormancy controls to be broken.
3. Differences in the edaphic conditions between the sites appeared to affect germination percentages after 1 year of burial. A difference in germination response between sites was observed for Carex acutiformis, Filipendula ulmaria and Lychnis flos-cuculi .
4. A significantly higher germination percentage was found at the Great Britain site for F. ulmaria in the phosphate treatment compared with the potassium treatment and the control after 1 year of burial. In contrast to many literature assessments no significant effects of fertilizer application was found after 2 years.
5. For all sites, except one in the Netherlands, the total number of seeds that germinated was lower in 1996 than in 1995.     

Seed‐enhancement combinations improve germination and handling in two dominant native grass species

The use of native grasses for both restoration and commercial purposes is becoming increasingly important globally. Many native grasses have limited success in seed‐based restoration (e.g. post‐mine rehabilitation) and commercial industries (e.g. agriculture) due to poor seed germination and handling. Seed‐enhancement technologies can assist in overcoming these barriers. This study aimed to use combinations of seed enhancements to overcome the germination and handling challenges in two dominant Australian native grass species with demand in restoration and commercial industries (Triodia wiseana C.A Gardner and Rytidosperma caespitosum [Gaudich.] Connor & Edgar). Selected enhancements included hydropriming (including inoculation with karrikinolide [KAR₁]), flash flaming, and seed coating. Combinations of these seed enhancements allowed improvements in both germination (by up to 55% and 18% for T. wiseana and R. caespitosum, respectively) and floret geometry (flowability, as measured through a mechanized seeder, improved by up to 6‐fold and 17‐fold for T. wiseana and R. caespitosum, respectively), with the order of enhancement application being important. The responses of each species to enhancements corresponded with key biological processes and ecological cues required for recruitment events in nature, such as fire and rainfall events. Triodia wiseana germination was driven by fire‐related cues (i.e. KAR₁, flaming), while R. caespitosum germination was highest in response to moisture‐related cues (i.e. hydro‐priming). Responses to seed enhancements (and combinations of) may have implications for the management and scaled use of the targeted species. This can assist in improving the restoration and commercial success of the study species, and potentially other grasses with germination and handling challenges, into the future.     

Risks of overharvesting seed from native tallgrass prairies

Seed supply often limits the size and scope of restoration projects that require active revegetation. To meet demand from more and larger tallgrass prairie restoration projects in the Great Plains, U.S.A., seed is wild‐harvested—collected from remnant habitats—using agricultural combine harvesters. We investigated the potential impacts of wild‐harvest by comparing prairie remnants of northwestern Minnesota that varied in their histories of harvest frequency but were otherwise similar. We asked: (1) Do wild‐harvested prairies differ in species composition from unharvested prairies? (2) If so, can life history traits be used to predict the response of prairie communities to wild‐harvest? We conducted a retrospective study of 17 prairies harvested for seed frequently (annually/biennially), infrequently (2–3 times), or not at all. We sampled vegetation at 45 points within each site, recording all species present within 0.25 m² quadrats. To address the first question, we used non‐metric multidimensional scaling and Mantel tests, followed by analysis of variance contrasts to identify any species less likely to occur on frequently harvested sites (“harvest‐negative”). For the second question, we used logistic regression to test whether lifespan, clonality, and seed production predicted harvest‐negative species. Plant community composition in frequently harvested prairies differed from that of infrequently or unharvested prairies. Fourteen species, generally short‐lived and non‐clonal, were classified as harvest‐negative. Our results suggest that frequent wild‐harvest disrupts reproduction of species relying on seed, and that life history traits may provide a basis for predicting a species' response to wild‐harvest.     

封育和放牧条件下退化荒漠草地土壤种子库特征

连续2年地不同退化程度天然干旱荒漠草原围封后群落的土壤种子库进行研究。结果显示,土壤种子库物种数、种子密度和植物生活型在年际间、封育与放牧样地间及退化梯度问均有明显差异。种子库物种数为封育高于放牧样地;退化梯度相比,物种数除2003年封育样地随退化程度加剧呈减少趋势外,放牧样地及2004年各样地均随退化程度加剧而增加。种子岸密度结果显示．2003年种子库密度明显高于2004年;各封育样地2年中土壤种子库密度显著或极显著（P＜0．01）高于放牧样地;退化梯度相比种子库密度除2003年封育样地随退化程度加剧而急剧增加外,其余各样地种均随退化程度加剧而明显下降。植被生活型分析结果为,2003年以一年生草本植物种出现频率最高,各样地分别达94．0％～98．4％．多年生草本及灌木出现频率则很低,分别为1．59％～5．15％和0．03％～0．4％,2004年则为多年小草本植物种比例上升．且显示出封育高于放牧、退化程度愈轻增幅愈大的趋势。2年的结果显示种子库物种Shannon－Wiener多样性指数和Peilow均匀性系数均以封育低于放牧样地。种子库密度与地上植被盖度相关性分析表．2年结果中仅一年生草本和2003年灌木的土壤种子库密度与相应地上植被盖度之间具相关趋势和显著（P〈0．01）相关。     

Evaluation of topsoil inversion in U.K. habitat creation and restoration schemes

Habitat creation and restoration schemes on former agricultural soils can be constrained by high residual soil fertility, a weedy seed bank, and a lack of suitable species in the seed rain. Topsoil inversion has been trialled across the United Kingdom as a novel technique to address these constraints. We investigated 15 topsoil inversion sites ranging in age (time since inversion) from 6 months to 5 years. We assessed surface soil fertility compared to adjacent noninverted soil, and vegetation composition with respect to the species introduced at each site. Soil organic matter, total and extractable N and P were lower in topsoil inversion surface soils, demonstrating that topsoil inversion can successfully reduce surface soil fertility prior to habitat creation and restoration. This reduction was maintained over the timescale of this study (5 years). Cornfield annual nurse crops provided instant visual appeal and gave way to grassland species over time. Sown species varied widely in their establishment success, and sowings were more successful than plug plantings. Grasses colonized naturally following sowing forb‐only seed mixes, allowing introduced forbs to establish early on with reduced competition from the seed bank. Plant communities did not yet resemble seminatural communities, but all were in the early stages of community development. Results indicate that topsoil inversion can successfully lower surface soil fertility and reduce competition between sown species and agricultural weeds.     

Geographic variation in the flood-induced fluctuating temperature requirement for germination in Setaria parviflora seeds

Our aim was to search for specific seed germinative strategies related to flooding escape in Setaria parviflora, a common species across the Americas. For this purpose, we investigated induction after floods, in relation to fluctuating temperature requirements for germination in seeds from mountain, floodplain and successional grasslands. A laboratory experiment was conducted in which seeds were imbibed or immersed in water at 5°C. Seeds were also buried in flood-prone and upland grasslands and exhumed during the flooding season. Additionally, seeds were buried in flooded or drained grassland mesocosms. Germination of exhumed seeds was assayed at 25°C or at 20°C/30°C in the dark or in the presence of red light pulses. After submergence or soil flooding, a high fraction (>32%) of seeds from the floodplain required fluctuating temperatures to germinate. In contrast, seeds from the mountains showed maximum differences in germination between fluctuating and constant temperature treatment only after imbibition (35%) or in non-flooded soil conditions (40%). The fluctuating temperature requirement was not clearly related to the foregoing conditions in the successional grassland seeds. Maximum germination could also be attained with red light pulses to seeds from mountain and successional grasslands. Results show that the fluctuating temperature requirement might help floodplain seeds to germinate after floods, indicating a unique feature of the dormancy of S. parviflora seeds from floodplains, which suggests an adaptive advantage aimed at postponing emergence during inundation periods. In contrast, the fluctuating temperature required for germination among seeds from mountain and successional grasslands show its importance for gap detection.     

Nitrogen addition decreases seed germination in a temperate steppe

Seed germination and seedling establishment play an important role in driving the responses of plant community structure and function to global change. Nitrogen (N) deposition is one of the driving factors of global change, which often leads to a loss in species richness in grassland ecosystems. However, how seed germination responds to N addition remains unclear. A pot incubation test was conducted in a semi‐arid grassland in the Mongolian Plateau, Northern China, to investigate the effect of N addition (0, 5, 10, 20, 40, and 80 g N/m²) on seed germination from May to October 2016. Twenty species germinated under all treatments; however, the responses of the 20 species to N addition were different. The densities of Stipa krylovii, Leymus chinensis, and Artemisia frigida, which are the dominant species in this temperate steppe, decreased significantly as the amount of N addition. Moreover, N addition significantly suppressed seedling densities of the community, perennial forbs, perennial grasses, and annuals and biennials. Furthermore, species richness of the community, perennial forbs, and annuals and biennials decreased sharply with increasing N addition level, but perennial grass species richness did not change. The Shannon–Wiener diversity index also decreased as the amount of N addition increased. Our results suggest that N enrichment plays an important role in the seed germination stage and decreases supplements of seedlings to adult plants. These findings may help explain the causes of species loss by atmospheric N deposition in grassland ecosystems.     

Composition,size and dynamics of the seed bank in a mediterranean shrubland of Chile

Abstract Analysis was performed of the richness and abundance of woody species, forbs, and annual grasses in the easily germinating soil seed bank (henceforth seed bank) in a mediterranean shrubland of central Chile. The effects of successional development after fire and by microsite type (underneath or outside shrubs) on the density of seeds in the soil, and the relationship of species abundance in the seed bank with its abundance in the above‐ground vegetation was examined. A total of 64 plant species were recorded in the seed bank, of which 44 were annual or biannual. Eight species were woody and another eight were perennial herbs. Four could not be identified to species level. The highest richness of established herbaceous species was recorded in late spring, with 31 species. The regeneration of the herbaceous vegetation was driven by the annual production of seeds and by a reserve of short‐lived propagules in the soil. Density of all germinating seeds was significantly higher during late spring and late summer. Density of grass seeds was greater during late spring, while that of all other species was greater during late summer. Annual grass seeds accumulated in higher proportion at exposed microsites rather than under woody canopy, and in young (< 5 years old) and intermediate‐age patches (10–20 years old) rather than in mature vegetation (30–50 years old). The abundance of established woody and herb species was uncorrelated with that of the seed bank.     

The Role of Soil Seed Banks in Natural Restoration of the Degraded Hunshandak Sandlands, Northern China

The density of seeds in soil seed banks and the species composition of both seed banks and aboveground vegetation were examined in naturally restored sites (NRS) and aerially seeded sites (ASS) in the Hunshandak sandlands of northern China. Five sites were naturally restored 1, 2, 4, 8, and 15 years ago and four sites were aerially seeded 1, 2, 5, and 7 years ago. In total, 36 species were recorded in the seed bank and 41 species in the aboveground vegetation for all NRS, whereas the numbers were 17 and 19, respectively, for ASS, indicating that the NRS can support higher diversity of species than the ASS. During the initial 2 years of restoration, introduced alien shrubs by aerial seeding dominated the vegetation of ASS, although there were indigenous pioneer species in the seed bank which failed to establish in the community. In contrast, indigenous species were dominant components in both the seed bank and the vegetation at the NRS. These findings suggest that the establishment of introduced species might have restricted the germination of certain indigenous pioneer species. Seed bank density of NRS significantly increased with time from 459 ± 76 seeds m⁻² at NRS2 to 3,351 ± 694 seeds m⁻² at NRS15, showing that the seed bank in degraded grassland is large enough to allow natural restoration. It is not always necessary to actively introduce seeds to enhance vegetation diversity.     

冷蒿草原土壤可萌发种子库特征及其对放牧的响应

（１）采用萌发试验法对内蒙古冷蒿（Ａｒｔｅｍｉｓｉａ ｆｒｉｇｉｄａ）草原土壤种子特征及其在不同放牧压力下的变化进行了研究。（２）冷蒿草原可萌发种子库由４种多年生禾草,１１种种多年生杂草及３种１年生植物所组成。（３）每样中的可萌发种子是变化于４５到３０５之间,平均１０２／样。多年生禾草、多年生杂类草及１年生植物的土壤中种子量分别占总可萌发种子库的４６．５７％、５１．９６％和１．５７％。多年和禾 草     

Cracking the case: Seed traits and phylogeny predict time to germination in prairie restoration species

Traits are important for understanding how plant communities assemble and function, providing a common currency for studying ecological processes across species, locations, and habitat types. However, the majority of studies relating species traits to community assembly rely upon vegetative traits of mature plants. Seed traits, which are understudied relative to whole‐plant traits, are key to understanding assembly of plant communities. This is particularly true for restored communities, which are typically started de novo from seed, making seed germination a critical first step in community assembly and an early filter for plant establishment. We experimentally tested the effects of seed traits (mass, shape, and embryo to seed size ratio) and phylogeny on germination response in 32 species commonly used in prairie grassland restoration in the Midwestern USA, analyzing data using time‐to‐event (survival) analysis. As germination is also influenced by seed dormancy, and dormancy break treatments are commonly employed in restoration, we also tested the effects of two pretreatments (cold stratification and gibberellic acid application) on time to germination. Seed traits, phylogeny, and seed pretreatments all affected time to germination. Of all traits tested, variables related to seed shape (height and shape variance) best predicted germination response, with high‐variance (i.e., pointier and narrower) seeds germinating faster. Phylogenetic position (the location of species on the phylogenetic tree relative to other tested species) was also an important predictor of germination response, that is, closely related species showed similar patterns in time to germination. This was true despite the fact that all measured seed traits showed phylogenetic signal, therefore phylogeny provided residual information that was not already captured by measured seed traits. Seed traits, phylogenetic position, and germination pretreatments were important predictors of germination response for a suite of species commonly used in grassland restoration. Shape traits were especially important, while mass, often the only seed trait used in studies of community assembly, was not a strong predictor of germination timing. These findings illustrate the ecological importance of seed traits that are rarely incorporated into functional studies of plant communities. This information can also be used to advance restoration practice by guiding restoration planning and seed mix design.     

A Photochemical Mechanism for Homochirogenesis. Part 2

A theoretical investigation of the photochemistry of racemic compounds with circularly polarized light was undertaken. The exact solutions of the differential equations by numerical integration to the approximate solutions used in an earlier article were compared. The exact solutions showed that sequential reactions yield enhanced optical activities in the products. For irreversible reactions, all enantiomeric excesses are lost if the reactions are carried to completion, but appreciable resolution occurs in many cases for partial conversion. For reversible reactions, significant enantiomeric excesses are found at the photostationary state. Chirality 25:16‐21, 2013. © 2012 Wiley Periodicals, Inc.     

Degradation of β-Conglycinin β-Homotrimer by Papain: Independent Occurrence of Limited and Extensive Proteolysis

Limited and extensive proteolysis occur when β-conglycinin β homo-trimer (β₃-conglycinin) from soybeans is attacked by papain. Slow limited proteolysis is restricted to cleavage of β₃-conglycinin polypeptides into subunit halves (N- and C-terminal domains) that are further slightly truncated. The kinetics of limited and extensive proteolyses analyzed separately indicates that the two processes occur independently from the very beginning of the reaction. In contrast, limited proteolysis of phaseolin from common beans has been found to be prerequisite for the onset of its extensive proteolysis. The dramatic distinction between the degradation patterns of β₃-conglycinin and phaseolin, homologous storage 7S globulins, suggests the existence of intrinsic differences in their structures. This hypothesis is supported by comparative analysis of the accessibilities to the solvent of amino acid residues in phaseolin and β₃-conglycinin structures, which indicated the relatively low packing density of the latter, resulting in enhanced susceptibility of it to extensive proteolysis.