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.     

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。     

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.     

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.     

Response of a rare herb (Trioncinia retroflexa) from semi‐arid tropical grassland to occasional fire and grazing

Trioncinia retroflexa (Asteraceae) is a rare perennial herb endemic to Dichanthium‐dominated grasslands on basaltic soils in central Queensland. Trioncinia lives for approximately 5 years and some seed remains viable in the soil for at least 18 months. Population densities increased sixfold over 4 years, coinciding with recovery during a period of above‐average rainfall after a 4‐year drought preceding this study. The species’ lifespan, which can exceed 5 years, coupled with its extended seed‐bank viability ensures that populations can endure drought despite low levels of seedling recruitment. The restricted occurrence of the species to spasmodically grazed stock routes provides evidence that Trioncinia is sensitive to the continuous grazing that typically occurs in paddocks. The hypothesis that the species requires occasional disturbance for survival was experimentally tested. Recruitment was depressed with burning and inflorescence production enhanced with both burning and simulated intense spasmodic grazing after the first application of treatments. However, these effects were not evident after a second application of the treatments and there were no significant effects of treatment on population densities at the completion of the 4‐year experiment. Although not requisite, sporadic dry‐season grazing and burning of these areas would appear to be compatible with the survival of Trioncinia. This project highlights the value of stock routes for rare plant conservation.     

Seasonal distribution of increased precipitation in maternal environments influences offspring performance of Potentilla tanacetifolia in a temperate steppe ecosystem

Aims Precipitation is predicted to increase in arid and semiarid regions under climate change, with greater changes in intra- and inter-annual distribution in the future. As a major limiting factor in these regions, changes in precipitation undoubtedly influence plant growth and productivity. However, how the temporal shifts in precipitation will impact plant populations are uncertain.     

Reduced germination success of temperate grassland seeds sown in dung: consequences for post‐dispersal seed fate

• Endozoochory is one of the main drivers shaping temperate grassland communities by maintaining plant populations of its constituents and enabling plants to colonize new habitats. Successful endozoochorous dispersal implies that seeds not only get consumed and survive the digestive tract but are also able to develop into viable seedlings in a dung environment.
• We experimentally assessed the germination probability and timing of 15 annual and perennial temperate European grassland species in cattle and horse dung and in different climatic conditions (greenhouse and outdoor conditions).
• Interspecific variation in germinability and germination timing are found, while life strategy had only an effect on germination timing. We found adverse effects of both cattle and horse dung on the germination characteristics of all tested grassland species, but the effects of cattle dung were more pronounced. In comparison with the control treatment, fewer seeds emerged in dung and more time was needed to germinate. Also, germination metrics clearly differed between the artificial greenhouse and outdoor conditions, with generally a lower germinability in outdoor conditions.
• According to our results, a large cost seems to be associated with endozoochorous dispersal in this stage of the life cycle, as seed dispersal effectiveness strongly depends on the quality of the deposition site with a lowered survival and germination probability when seeds are deposited in dung.

     

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 Western (Basalt) Plains grassland. 2. Field emergence, establishment and recruitment following direct seeding

Summary   Both reservation of small remnants and ecological restoration of degraded areas will be crucial if the Victorian Western (Basalt) Plains grassland community is to be conserved in the long term. This study examined the potential of direct seeding as a technique for grassland restoration by recording the initial establishment and subsequent recruitment success of 64 (predominantly perennial) grassland species direct sown onto a constructed site. Forty-three (67%) of the sown species emerged and established during the 2-year study and a further three species were recorded in subsequent years. In the second year, 32 species increased their number either through seedling or vegetative recruitment and 30 species dispersed beyond their original sown plot. Seed size was not correlated with field emergence but life form did influence initial field success for some groups. The finding that many species are able to establish and recruit under the study conditions supports the need for further investigation of direct seeding in the restoration of grassland communities.     

放牧方式影响高寒草地矮生嵩草种子大小与数量的关系

种子大小和种子数量变异是植物适合度研究的核心问题, 探究不同大型草食动物对嵩草(Kobresia spp.)草地优势种种子大小与数量的影响, 有助于了解其繁殖策略和种群更新机制。该研究依托青藏高原高寒草地-家畜系统适应性管理技术平台, 对不放牧(对照)、牦牛单牧、藏羊单牧、牦牛藏羊1:2混牧、牦牛藏羊1:4混牧、牦牛藏羊1:6混牧6个放牧处理下矮生嵩草(K. humilis)的种子大小和数量特征, 种子大小和数量与生殖性状的关系, 种子大小和数量的权衡关系进行研究。结果显示: 1)放牧处理增加矮生嵩草种子大小15%以上, 增加种子数量30%以上; 除了牦牛藏羊1:2混牧处理, 其他放牧处理与对照相比种子大小变异系数降低15%以上, 种子数量变异系数降低25%以上。2) Pearson相关分析结果显示, 放牧处理下矮生嵩草种子数量、种子大小与生殖相关性状均呈正相关关系。3)放牧处理增加了矮生嵩草种子大小与数量的权衡, 单条生殖枝质量是影响种子大小与数量权衡的重要性状。研究表明, 即使是中度放牧, 家畜依旧是矮生嵩草资源获取的限制性因子; 长期的放牧改变了矮生嵩草性状间的潜在联系和权衡关系, 稳定了种子大小和种子数量特征, 并通过提高种子大小和种子数量的方式优化繁殖策略, 提高了子代的竞争力和适合度。     

Influence of Seed Mixture and Hydrological Regime on the Establishment of a Diverse Grassland Sward at a Site with High Phosphorus Availability

Abstract Three experiments were undertaken to investigate the influence of seed mixture on the establishment of a target grassland community on a site with high available phosphorus. In the first experiment autumn‐ and spring‐sown commercial seed mixtures were compared with seed harvested from a nature reserve with respect to their ability to produce an inundation grassland community similar to that described by the British National Vegetation Classification (NVC) as Agrostis stolonifera–Alopecurus geniculatus grassland (MG13). In the second experiment the composition and sowing rate of a commercial seed mixture were altered to investigate whether these factors were significant in the establishment of a sward similar to MG13. Similarly, in the third experiment the composition of a commercial seed mixture designed to achieve an alternative community, Cynosurus cristatus–Caltha palustris grassland (NVC code MG8), was sown. The vegetation resulting from each of these treatments was monitored with permanent quadrats for a 3‐year period, and the hydrological regime of each quadrat location was modeled and quantified. The results showed that seed mixture, timing of sowing, and seeding rate had an initial effect on the vegetation that established. However, by the third year of monitoring there were no significant differences between these treatments, and hydrological regime had become the most important factor in determining the distribution of species. The vegetation was less diverse than predicted from germination tests and decreased in diversity over the monitoring period. It is suggested that this may be a result of the hydrological regime being unsuitable for several of the sown species or due to the extremely high available phosphorus concentration in the soil. This study highlights the need to understand the soil and hydrological conditions of a site before choosing a target community and designing a seed mixture.     

苜蓿种子萌发和幼苗生长对温度、光照和埋深的响应

紫花苜蓿(Medicagosativa)是世界人工草地重要的优良牧草.研究其种子萌发和幼苗生长对温度、光照及埋深等环境因子的响应,对苜蓿草地的种植及管理具有重要的实践指导意义.采用室内控制实验,分析了紫花苜蓿种子萌发和幼苗生长对恒温(10、15、20、25、30℃)、变温(6/15、10/20、15/25、15/30、...