Seed size effects on plant establishment under low atmospheric CO2, with implications for seed size evolution

Background and AimsLow atmospheric CO₂ concentration depresses photosynthesis and resource use efficiency, and therefore can inhibit phases of the life cycle such as seedling establishment. Seed reserves can compensate for photosynthetic inhibition by accelerating seedling growth. We therefore hypothesize that seedlings arising from large seeds show less inhibition from low atmospheric CO₂ than young plants from small seeds. Seed size effects on seedling responses to low CO₂ may also be enhanced in warm environments, due to greater photorespiration at high temperature.Methods Phaseolus and Vigna seeds differing in mass by over two orders of magnitude were planted and grown for 14 d in growth chambers with CO₂ concentrations of 370, 180 or 100 ppm, in thermal regimes of 25 °C/19 °C, 30 °C/24 °C or 35 °C/29 °C (day/night). We measured leaf area expansion, shoot growth and mortality of the seedlings arising from the variously sized seeds at 14 days after planting (14 DAP).Key ResultsRelative to small-seeded plants, large-seeded genotypes produced greater leaf area and shoot mass at 14 DAP across the range of CO₂ treatments in the 25 °C/19 °C and 30 °C/24 °C regimes, and at 100 ppm in the 35 °C/29 °C treatment. The proportional decline in leaf area and seed mass with CO₂ reduction was generally greater for seedlings arising from small than from large seeds. Reductions in leaf area due to CO₂ reduction increased in the warmer temperature treatments. In the 35 °C/19 °C treatment at 100 ppm CO₂, seedling mortality was greater in small- than in large-seeded genotypes, and the small-seeded genotypes were unable to exit the seedling stage by the end of the experiment.ConclusionsThe results support a hypothesis that seedlings from large seeds grow and establish better than seedlings from small seeds in warm, low CO₂ environments. During low CO₂ episodes in Earth’s history, such as the past 30 million years, large seeds may have been favoured by natural selection in warm environments. With the recent rise in atmospheric CO₂ due to human activities, trade-offs between seed size and number may already be affected, such that seed size today may be non-optimal in their natural habitats.     

Seed size and plant strategy across the whole life cycle

We compiled information from the international literature to quantify the relationships between seed mass and survival through each of the hazards plants face between seed production and maturity. We found that small-seeded species were more abundant in the seed rain than large-seeded species. However, this numerical advantage was lost by seedling emergence. The disadvantage of small-seeded species probably results from size-selective post-dispersal seed predation, or the longer time small-seeded species spend in the soil before germination. Seedlings from large-seeded species have higher survival through a given amount of time as seedlings. However, this advantage seems to be countered by the greater time taken for large-seeded species to reach reproductive maturity: our data suggested no relationship, or perhaps a weak negative relationship, between seed size and survival from seedling emergence through to adulthood. A previous compilation showed that the inverse relationship between seed mass and the number of seeds produced per unit canopy area per year is countered by positive relationships between seed mass, plant size and plant longevity. Taken together, these data show that our old understanding of a species' seed mass as the result of a trade–off between producing a few large offspring, each with high survival probability, versus producing many small offspring each with a lower chance of successfully establishing was incomplete. It seems more likely that seed size evolves as part of a spectrum of life history traits, including plant size, plant longevity, juvenile survival rate and time to reproduction.     

Importance of seed size for the establishment of seedlings of five deciduous broad-leaved tree species

Effects of seed size and phenology on the establishment of five deciduous broad-leaved tree species were examined in deciduous woodland. Treatments included absence and presence of litter in the forest understory, a small gap, and a large gap. Seedling emergence of large-seeded speciesQuercus mongolica var.grosseserrata andAcer mono was not reduced by accumulation of litter in the forest understory, but was promoted in the large gap where litter was less. Seedling emergence of small-seeded species,Alnus hirsuta, Cercidiphyllum japonicum andBetula platyphylla var.japonica, was reduced by the litter in almost all of the sites. Seedlings of large-seeded species avoid shade stress phenologically by unfolding all of their large leaves in a short period before canopy closure in the forest understory. These species had little mortality after seedling emergence. In contrast, small-seeded species have a longer duration of leaf emergence, shorter leaf longevity, and rapid leaf turnover in all the sites. These seedlings attained similar height to those of the large-seeded species at the end of the second year in the large gap, but survival and height growth rate decreased after canopy closure in the forest understory. We suggest that the importance of seed size in determining seedling establishment largely depends on the relationships between seasonal changes of environmental conditions and phenological traits of seedlings, which are related to seed size.Abbreviations Ah Alnus hirsuta - Am Acer mono - Cj Cercidiphyllum japonicum - Bp Betula platyphylla var.japonica - Qm Quercus mongolica var.grosseserrata     

种子大小和干旱胁迫对辽东栎幼苗生长和生理特性的影响

在温室内遮阴条件下,设置80%、60%、40%和20%田间持水量(对照、轻度、中度和重度干旱)4个处理,研究种子大小和干旱胁迫对盆栽辽东栎幼苗生长和生理特性的影响。结果表明:大种子(3.05±0.38 g)幼苗的单株叶面积、总干质量和根冠比在所有处理均显著大于小种子(1.46±0.27 g)幼苗,前者的株高、基径、叶片数、比叶面积、相对生长率和净同化率等生长参数在轻度、中度和重度干旱处理均不同程度大于后者。大种子幼苗叶片过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性均高于小种子幼苗,前者叶片丙二醛(MDA)、可溶性蛋白、游离脯氨酸含量和叶绿素总量在部分干旱处理显著大于后者。除根冠比外,其他生长参数均随干旱胁迫增强逐渐减小,重度干旱处理大、小种子幼苗总干质量分别比对照降低19.4%和20.0%。POD、CAT和SOD活性均随干旱胁迫增强先升后降,在中度干旱处理,大、小种子幼苗POD活性分别显著高于对照126.7%和142.1%,CAT活性分别显著高于对照170.0%和151.9%。在重度干旱处理,大、小种子幼苗MDA含量分别显著高于对照86.5%和68.9%。可...     

Effect of seed size and plant growth on nodulation and nodule development in lima bean (Phaseolus lunatus L.)

Lima bean (Phaseolus lunatus L.) cultivars vary widely in their growth habit and seed size. Preliminary experiments indicated that a large-seeded pole cultivar (King of the Garden) formed many more nodules than a small-seeded bush cultivar (Henderson). The relative importance of seed size and shoot mass in determining nodule number and mass was assessed in five lima bean cultivars differing in seed size and growth habit. Between cultivars, significant positive correlations between initial seed mass, plant weight and nodule number and mass were observed during the first four weeks after planting. Comparisons within cultivars indicated a strong correlation between nodule mass and shoot dry weight. The influence of plant morphology on nodule formation and mass was secondary to the effects of seed and shoot mass. As plants matured, the increase in nodule mass paralleled the increase in plant mass, while nodule number was relatively stable after day 18. These results suggest that the highly regulated process of nodule formation was under the influence of seed derived factors, while the continued accumulation of nodule tissue was related to shoot growth.     

Seed size and seedling emergence: an allometric relationship and some ecological implications

We develop a geometric model predicting that maximum seedling emergence depth should scale as the cube root of seed weight. We tested the prediction by planting seeds from 17 species ranging in weight from 0.1 to 100 mg at a variety of depths in a sand medium. The species were spread across 16 genera and 13 families, all occurring in fire-prone fynbos shrublands of South Africa. Maximum emergence depth was found to scale allometrically with seed weight with an exponent of 0.334, close to the predicted value. We used the allometry to predict recruitment response to experimentally simulated variation in fire intensity. Five species with small (<2 mg) seeds and five with large (>10 mg) seeds were planted at ≤20-mm and 40-mm depths and exposed to low and high heat treatments and a control. The allometric equation predicted that species with large seeds would be able to emerge from a depth of 40 mm but those with small seeds would not. Only 1% of 481 seedlings from small-seeded species emerged from the 40-mm planting compared with 40% of 626 seedlings from the large-seeded group. The simulated fire treatments killed seeds in shallow, but not deeper, soil layers. At simulated high fire intensities, seedling emergence was poor in small-seeded species but good in large-seeded species, with most seedlings emerging from the 40-mm planting depth. Seed size could be a useful general predictor of recruitment success under different fire intensities in this system. We suggest that allometric relationships in plants deserve wider attention as predictive tools. Received: 28 September 1998 / Accepted: 3 March 1999     

THE EFFECT OF SEED SIZE AND MATERNAL SOURCE ON INDIVIDUAL SIZE IN A POPULATION OF LUDWIGIA LEPTOCARPA (ONAGRACEAE)

Seed size is normally distributed for many annual species, while mature plant size is frequently positively skewed. A study was conducted to determine the influence of seed size and the role of genetic differences in determining relative seedling size for Ludwigia leptocarpa. Seed size had a significant effect on percentage germination and time of seed germination but no effect on dry weight or leaf area of seedlings. Seed size and spacing had a significant effect on seedling dry weight for plants grown under competition, while relative day of emergence had no effect. Familial (genetic) differences were found in average seed weight between maternal plants, but not in average number of days to germination, average weight of seeds which germinated, or shoot dry weight. It is concluded that neither seed size alone nor genetic differences between plants are directly responsible for the development of size hierarchies in Ludwigia leptocarpa populations. Large seed size does convey an advantage in growth when plants from seeds of differing initial size interact.     

Seed size and recruitment limitation influence seedling establishment in three tallgrass prairie species

A seed size–seed number tradeoff predicts that large numbers of seeds have an establishment advantage under low levels of competition, while large seed size is advantageous under asymmetric competition. Testing these predictions in the context of tallgrass prairie restoration should increase predictability of outcomes of species composition—restoration technique combinations. I conducted field and greenhouse experiments comparing seedling establishment among three tallgrass prairie species with different seed mass-seed number combinations, but with similar mass of seeds sown. Species were prairie dock [Silphium terebinthinaceum, mass = 33.2 + 2.1 mg ( \(\overline{x}\)  + SE, n = 100)], wild quinine (Parthenium integrifolium, mass = 3.1 + 0.3 mg), and smooth blue aster (Symphyotrichum laeve var. laeve, mass = 0.53 + 0.02 mg). Seeds were sown into mowed or tilled plots with shade and mulch treatments in an old field in northeastern Illinois USA, and seeds were sown into containers with or without vegetative cover in a greenhouse. In mowed plots, species with larger numbers of seeds sown had higher seedling densities. In tilled plots, seedling densities of the large-seeded Silphium were reduced less by shade than the small-seeded Parthenium. Symphyotrichum, however, did not respond to treatments as expected based on its seed size. High relative growth rate possibly increased Symphyotrichum seedling establishment in competitive environments. Results of this study demonstrated recruitment limitation when seedlings established into existing vegetation, and suggest that species composition resulting from specific seeding rates during prairie restoration may be more predictable when species are interseeded into existing vegetation, than when seeds are sown into tilled fields.     

Seed size: a key trait determining species distribution and diversity of dry tropical forest in northern India

The study examined the relationships among seed size, plant distribution and abundance in a dry tropical forest of northern India. Results indicated that small-seeded species, which were generally wind-dispersed, were more widely distributed, at this local scale, compared to large-seeded species. However, the proportional abundance and basal cover of seed size categories indicated that the structure of the dry forest was largely determined by the medium- to large-seeded species. There was a considerable amount of redundancy within each seed size group, which added to the species diversity. Variability in seed size and the variable degree of shade-tolerance permit the species to occupy the full range of the gradient of light environments of the forest floor. This study revealed that in little to moderately disturbed locations seedlings of large-seeded species increased in abundance, whereas in extremely perturbed locations seedlings of species with medium-sized to small seeds were more abundant.     

Germination responses to water potential in neotropical pioneers suggest large-seeded species take more risks

Background and Aims

In neotropical forests, very small-seeded pioneer species (<0·1 mg seed mass) recruit preferentially in small tree fall gaps and at gap edges, but large-seeded pioneers do not. Since water availability is related to gap size, these differences in microsite preference may reflect in part species-specific differences in germination at reduced water potentials.

Methods

For 14 neotropical pioneer species, the hypothesis is tested that small-seeded species, with shallow initial rooting depths, reduce the risks associated with desiccation by germinating more slowly and at higher water potentials than large-seeded species.

Key Results

Germination occurred both more quickly and at lower water potentials with increasing seed mass. For example, Ochroma pyramidale (seed mass 5·5 mg) had a time to 50 % germination (T₅₀) of 2·8 d and a median base potential for germination (ψ_b50) of −1·8 MPa while Clidemia quinquenervia (seed mass 0·017 mg) had a T₅₀ of 17·6 d and ψ_b50 of −1·1 MPa.

Conclusions

These data suggest that small-seeded species germinate only in comparatively moist microsites, such as small canopy gaps, which may reduce the risk of drought-induced mortality. Conversely, large-seeded species are able to germinate in the drier environment of large gaps, where they benefit by enhanced seedling growth in a high irradiance environment. The positive association of seed size and canopy gap size for optimal seedling establishment is maintained by differential germination responses to soil water availability coupled with the scaling of radicle growth rate and seed size, which collectively confer greater drought tolerance on large-seeded species.Key words: Germination, seed size, Panamá, neotropical, pioneer, water potential     

Non-native grass invasion suppresses forest succession

Multiple factors can affect the process of forest succession including seed dispersal patterns, seedling survival, and environmental heterogeneity. A relatively understudied factor affecting the process of succession is invasions by non-native plants. Invasions can increase competition, alter abiotic conditions, and provide refuge for consumers. Functional traits of trees such as seed size and life history stage may mediate the effects of invasions on succession. We tested the effects of the forest invader Microstegium vimineum on planted and naturally regenerating trees in a multi-year field experiment. We established plots containing nine species of small- and large-seeded tree species planted as seeds or saplings, and experimentally added Microstegium to half of all plots. Over 3 years, Microstegium invasion had an overall negative effect on small-seeded species driven primarily by the effect on sweetgum, the most abundant small-seeded species, but did not affect large-seeded species such as hickory and oak species, which have more stored seed resources. Natural regeneration was over 400% greater in control than invaded plots for box elder, red maple, and spicebush, and box elder seedlings were 58% smaller in invaded plots. In contrast to the effects on tree seedlings, invasion did not affect tree sapling survival or growth. Microstegium may be directly reducing tree regeneration through competition. Invaded plots had greater overall herbaceous biomass in 2006 and 2008 and reduced light availability late in the growing season. Indirect effects may also be important. Invaded plots had 120% more thatch biomass, a physical barrier to seedling establishment, and significantly greater vole damage to tree saplings during 2006 and 2007. Our results show that two tree functional traits, seed size and life history stage, determined the effects of Microstegium on tree regeneration. Suppression of tree regeneration by Microstegium invasions may slow the rate of forest succession and alter tree species composition.     

Seed size,establishment sites and species coexistence in a Chilean rain forest

Abstract. Seedling densities on the forest floor and on elevated microsites (logs and stumps) were compared for eight woody species in a temperate rain forest in southern Chile. Degree of association with elevated microsites varied significantly between species, showed no systematic relationship with reported shade tolerance, but was significantly negatively correlated with seed mass. Large-seeded Podocarpus nubigena established preferentially on undisturbed forest floor sites, whereas seedlings of small-seeded species such as Nothofagus nitida and Laurelia philippiana were found mainly on fallen logs and stumps. The abundance of large seedlings and saplings of N. nitida on logs/stumps, and the growth forms of canopy trees, confirm that recruitment of this species occurs mainly on decaying wood. The relationship between seed size and microsite preferences may be caused by effects of seed size on (1) ability to establish in forest floor litter and (2) retention of seeds on logs. Seedling occupancy of logs and stumps varied with state of decay. Few seedlings of any species were present on logs in the early stages of decay. N. nitida established earlier than the other species, attaining maximum abundance on wood in the middle decay classes. Species richness and overall seedling abundance were highest on wood in advanced stages of decay. Seed size differences are suggested as a determinant of differential utilization of forest floor heterogeneity, and hence of plant species coexistence.     

Granivory in California sage scrub: implications for common plant invaders and ecosystem conservation

Seed predation may influence community assembly and invasion dynamics when seed predators preferentially select some seed species over others. However, the role of different seed predators and their preferences for seeds in multiple ecological contexts, including the endangered California sage scrub ecosystem, remain unresolved making predictions about which processes limit or promote invasions difficult. In addition, selection criteria, specifically how seed size and biogeographic origin (native versus invasive) influences selection, requires further research across multiple granivore guilds. We examined seed predator preference for common native and invasive seeds across small and large seed classes using seed dish experiments with motion-sensor video observation. We also quantified the relative importance of ants, birds, and mammals as seed predators in sage scrub. Community-wide, granivores preferred the small-seeded invasive mustard Brassica nigra, avoided the large-seeded invasive grass Bromus rubens and the native large-seeded shrub Encelia californica, and did not show significant selection or avoidance for the small-seeded native shrub Salvia apiana. Birds, notably California towhees (Melozone crissalis), were the most frequent granivore while rodents and ants rarely removed seeds. This study reveals that birds are important seed predators in California sage scrub and have the potential to contribute to biotic resistance to mustard invasions (Brassica nigra and potentially others).

     

Sabal palmetto seed size: causes of variation,choices of predators,and consequences for seedlings

High variation in seed size, as is common among angiosperms, may be maintained in a plant species when several factors select for seed size. Variation may also result from differences among adult plants, such as nutrient and water availability or the amount of photosynthetic tissue. In a study of Sabal palmetto seed ecology I found high seed size variation both within- and among-palms, and investigated possible factors maintaining this variation. Seed size was positively correlated with the number of leaves on parent palms. Larger seeds produced more vigorous seedlings that had greater leaf length, area, and mass, and greater root mass. Caryobruchus gleditsiae (Bruchidae: Coleoptera), whose larvae develop within palm seeds, preferentially oviposited on larger seeds, which in turn produced larger beetle offspring. By choosing the largest seeds available, ovipositing beetles thus affect both the quantity and the quality of seeds available for recruitment. I conclude that because beetle predation selects against large seeds, while larger seeds promote seedling vigor, the maintenance of seed size variation may be an adaptation of S. palmetto promoting both seed escape from predators and seedling vigor.     

Influence of seed size on dispersal patterns of woolly monkeys (Lagothrix lagothricha) at Tinigua Park, Colombia

Seed size in tropical forests is expected to vary in relation to dispersal mode, recruitment requirements and the nature of seed enemies in each community. Some studies have emphasized an advantage of large-seeded species in environments subject to low rates of disturbance, but at the same time the number of dispersers tends to decrease as seed size increases. In this paper we describe how seed size affects the probabilities of seed dispersal by woolly monkeys at Tinigua National Park and we compare dispersal patterns among age/sex classes. The results are based on 1236 fecal samples recovered from focal individuals during two years. Woolly monkeys are able to swallow wide seeds; however, there seems to be a limit imposed by anatomical constraints that does not allow them to swallow seeds wider than 18 mm. Most of the seed mass dispersed by the monkeys falls in the categories between 6 and 12 mm wide. Seed selection in terms of mass was not observed for small-seeded species, but it was observed for some of the medium sized species (without any clear size preference) and there was a clear tendency to swallow relatively small seeds from the large-seeded species. Although we did not observe a difference in the number of seeds dispersed by deposition among age/sex classes, juveniles disperse a lower seed mass than adult animals. These differences highlight that different age/sex categories play distinct ecological roles in terms of seed dispersal processes. Seed selection by primates might impose selection pressures in seed size traits, but more studies are necessary to ascertain their potential evolutionary role.     

Seed size as an indicator of seed quality: a case study of Primula veris

Seed size is a widely accepted measure of seed quality, because many earlier studies have shown that large seeds have high seedling survival, growth and establishment. We tested whether ovule loss increases size of the remaining seeds and whether such size increase affects seedling establishment. We removed all except one flower from inflorescences of Primula veris L. (Primulaceae), a perennial hemicryptophyte herb, at a late stage of flowering. Flower removal (FR) increased seed size by 33% compared to the control plants. We then divided the seeds within each treatment to small, middle-sized and large seeds and carried out a sowing experiment in the field. Within each experimental group, seedling establishment was positively associated with seed size. However, despite size differences, seeds from the FR and control groups had the same seedling establishment probability. Seeds from FR plants had a higher seedling emergence in May than those from control plants, but the number of seedlings alive per sowing plot in the late summer was the same in both experimental groups. Increase in seed mass after partial FR thus did not enhance seedling performance, although seed size variation due to other causes was positively correlated with seedling establishment. Further studies are needed to show whether plastic changes of seed size are usually adaptive or not.     

Impacts of secondary seed dispersal and herbivory on seedling survival in Aesculus turbinata

Abstract. Aesculus turbinata is a tree species with large seeds (6.2 g mean dry weight). We studied the demography of its seeds and seedlings in a temperate deciduous forest in northern Japan to elucidate the ecological significance of large seeds with special reference to herbivory and secondary dispersal. Both seed and seedling stages suffered greatly from herbivores. Seedling herbivory was important judged from experiments with shoot clipping and hypogeal cotyledon removal. However, some seedlings survived through re-sprouting after herbivory. Survival rate and percentage resprouting seedlings were lower than those with remaining cotyledons, though seedling size was not affected. This suggests that stored resources in hypogeal cotyledons are working as a kind of ‘risk hedge’ against severe aboveground shoot clipping experienced by A. turbinata. The spatial distribution of seedlings was expanded via seed scatter-hoarding by rodents. Seedling survival rate was higher within canopy gaps than under closed canopy, indicating that canopy gaps are safe sites for establishment, and was negatively correlated with seedling density. Therefore, secondary seed dispersal in this species seems to be effective in ‘finding’ safe sites and in ‘escaping’ density-dependent mortality. The large seeds and seedlings of A. turbinata are attractive to herbivores, but the high resistance of seedlings to herbivory due to large reserves and the effective secondary dispersal appear to mitigate these disadvantages.     

Single-Seeded Fruits and Seedling Establishment in Dalbergia miscolobium Benth. (Papilionaceae)1

Dalbergia miscolobium (Papilionaceae) is a tree of the Brazilian cerrado that produces ovaries with two ovules. Only one ovule usually matures, but when two mature, they are smaller than seeds of single-seeded pods. Germination percentage was lower in small seeds than in medium or large seeds. In general, small seeds gave rise to smaller seedlings (dry mass) than did medium and large seeds. The root/shoot ratio, however, was very similar for the first six months, indicating that this ratio is consistent across seedling sizes. There was no correlation between seed size and relative growth rate. Single-seeded fruit production in D. miscolobium resulted in greater seed reserves and increased fruit dispersal distance; single-seeded fruits were lighter than double-seeded ones. Together, these two features should increase the probability of successful seedling establishment of seeds from single-seeded versus double-seeded fruits.     

The importance of seed reserves for seedling performance: an integrated approach using morphological,physiological, and stable isotope techniques

To investigate how seed reserves affect early seedling performance, we conducted a factorial greenhouse experiment using Lithocarpus densiflora (Tanoak). Seedlings were grown from large (5.8±0.7 g) and small (3.2±0.4 g) seeds and, following shoot emergence, seeds were either removed or left attached. Seedlings were harvested for quantification of biomass and ¹³C at seven time periods following seed removal (2, 4, 8, 16, 32, 64, 128 days) and seedling photosynthesis was measured three separate time periods (2–4, 49–82, 95–128 days after seed removal). Biomass increased for all seedlings, but the increase was significantly larger for seedlings with attached seeds than with removed seeds. Seed removal just after shoot emergence significantly decreased seedling biomass, but seed removal 64 days after shoot emergence had no effect on seedling biomass. Seedling photosynthesis per unit leaf area varied by time and seed presence, but not by seed size. At the first period, seedlings with attached seeds had significantly higher photosynthetic rates than seedlings with removed seeds, at the second period there was no effect of seed removal, and at the third time period seedlings with attached seeds had significantly lower photosynthetic rates than seedlings with removed seeds. Despite temporal variation in photosynthesis per unit leaf area, seedlings with attached seeds always had significantly greater leaf area than seedlings with removed seeds, resulting in significantly higher total plant photosynthesis at all three time periods. The ¹³C values of both the leaves and roots were more similar to that of the seed for seedlings with attached seeds than for seedlings with removed seeds, however, seed removal and seed size strongly affected root ¹³C. This study demonstrates that seed reserves have important effects on the early growth, physiology, and ¹³C of L. densiflora seedlings.     

Effects of litter on seedling establishment: an indoor experiment with short-lived Brassicaceae species

Recruitment by seeds is essential both in vegetation dynamics and in supporting biodiversity in grasslands. The recruitment by seeds is feasible in suitable vegetation gaps from the seed rain and/or by establishment from persistent soil seed banks. Cessation of grassland management results in litter accumulation, which leads to the decline of species diversity by the decreased availability of open patches. Low amounts of litter is often beneficial, while high amounts of litter is detrimental for seed germination and seedling establishment of short-lived species. In a designed indoor experiment, we explored the effect of litter on seedling establishment by germinating six short-lived Brassicaceae species with both increasing seed mass and litter cover. We found that both seed mass and litter had significant effect on germination and establishment of the sown species. Small-seeded species were significantly negatively affected by the 300 and/or 600 g/m² litter layers. No negative litter effect was detected for species with high seed masses (Lepidium spp.). No overall significant positive litter effect was found, although for most of the species cumulative seedling numbers were not the highest at the bare soil pots. Our results suggest that the negative effects of litter are less feasible on the large-seeded short-lived species than on that of small-seeded ones.