Post‐dispersal probability of germination and establishment on the shorelines of slow‐flowing or stagnant water bodies

Sarneel, Judith M.; Soons, Merel B.

doi:10.1111/j.1654-1103.2011.01367.x

Cited by 16 publications

(17 citation statements)

References 30 publications

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“…This was done under ‘field capacity’ (the amount of water left in the sediment when excess water has been drained) and ‘waterlogged’ conditions (water‐saturated sediments), representing two realistic field moisture conditions. Results showed that, in contrast to a study with slightly different mesh bags (Sarneel & Soons ), enclosing seeds in mesh bags lowered germination proportions for all species on average (±SD) from 0·50 (±0·23) to 0·30 (±0·22) under field capacity, and from 0·56 (±0·28) to 0·41 (±0·19) under waterlogged conditions. Crucially, the effect of mesh bags was similar between moisture treatments.…”

Section: Methodscontrasting

confidence: 86%

Early plant recruitment stages set the template for the development of vegetation patterns along a hydrological gradient

et al. 2015

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Summary1. Recruitment processes are critical components of a plant's life cycle. However, in comparison with later stages in the plant life cycle (e.g. competition among adults), relatively little is known about their contribution to the regulation of plant species distribution. Particularly, little is known about the individual contributions of the three main recruitment processes -germination, seedling survival and seedling growth -to community assembly, while quantitative information on these contributions is essential for a more mechanistic understanding of the regulation of plant species distribution and biodiversity. 2. Riparian zones along streams provide a globally-relevant case study for evaluating the importance of the different stages of plant recruitment. The natural hydrological gradients of stream riparian zones are currently being restored after a period of world-wide habitat degradation. To identify how recruitment contributes to vegetation patterns and biodiversity in riparian zones, we carried out field experiments at restored lowland streams. We quantified the germination of introduced seeds, and survival and growth of introduced seedlings of 17 riparian plant species across a gradient from the stream channel to upland. 3. The hydrological gradient of riparian zones acted as a strong environmental filter on all three recruitment processes, through imposing an abiotic limitation (excess water) at low elevations and a resource limitation (water shortage) at higher elevations. Other variables, such as soil organic matter content and nutrient availability, only affected recruitment marginally. 4. Species-specific patterns of environmental filtering initiated niche segregation along the riparian gradient during all three recruitment processes, but particularly during germination and seedling growth. These recruitment niches appeared strongly related to indicator values for adult distribution optima, suggesting that at least some riparian plant species may have evolutionary adaptations that promote recruitment under favourable hydrological conditions for adult growth and reproduction. 5. Our results suggest that strong environmental filtering during germination and seedling growth plays an important role in determining later adult distributions, by forming the spatial template on which all subsequent processes operate. In addition to well-known mechanisms, such as competitive exclusion at the adult stage, environmental filtering during early recruitment stages already strongly affect plant distribution and diversity.

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Section: Methodscontrasting

confidence: 86%

Early plant recruitment stages set the template for the development of vegetation patterns along a hydrological gradient

et al. 2015

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“…In a natural environment, this may happen when cypselae find themselves in contact with the substrate at river's edge after flash flooding, or when they are washed out from irrigation canals. This event has also been observed on exposed banks after dispersal (Sarneel & Soons ). A post‐flooding survey of soil seed bank of riparian corridors should be considered in downstream regions of highly infested area, and further control should be applied to prevent water spread in those area that parthenium weed has been detected.…”

Section: Discussionsupporting

confidence: 60%

Spread pathways of the invasive weed Parthenium hysterophorus L.: The potential for water dispersal

et al. 2019

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Parthenium hysterophorus L. (Asteraceae) utilises multiple mechanisms to facilitate its dispersal. It has been speculated that the cypsela, the propagule of this species, can be dispersed by water under varying environmental conditions. Four experiments were conducted to test this hypothesis, using simulated shaking and immersion to test floating ability and viability of the propagule in water. The influence of the acidity of the immersion medium on cypsela viability was also examined. Our results revealed that the freshly harvested cypselae could float on river water for at least 20 days, although around 80% sank within a week if moderate or severe turbulence was applied. Sinkage was observed to be more rapid in naked seeds (within a day) than in cypsela (within a week). On still water surfaces, germination occurred within a week but extended to 1.5 weeks under turbulent conditions due to sinkage. In river water, initial germination of floating cypselae was greater (70%) under illuminated conditions as compared to dark conditions (20%). The viability of immersed cypselae was found to remain high in distilled water for 45 days, when immersion was in cool conditions (10 or 15°C). However, in moderate (20 and 24°C) or warm (25 and 30°C) conditions, the rate of viability loss increased, and at 34°C, around 50% of the cypselae died after 20 days of immersion. Similar trends for cypselae longevity were observed in studies using river and pond water; viability loss was faster, especially in pond water. In summary, a proportion of cypselae will float in turbulent water and could be carried significant distances in river systems. Immersed cypselae can remain viable for weeks and can germinate on contact with soil. Water bodies or floods are therefore considered as important pathways in parthenium weed dispersal; hence, post-flood monitoring is strongly recommended to minimise its spread.

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“…At the community level, we found that germination of both seeds emerging from the seed bank and those dispersed into the mats responded to the flooding regime following unimodal relationships, indicating distinct optimal germination conditions. The overall lower germination in the field suggests that a field situation provides strong additional restrictions on recruitment (Sarneel & Soons ).…”

Section: Discussionmentioning

confidence: 99%

Windows of opportunity for germination of riparian species after restoring water level fluctuations: a field experiment with controlled seed banks

Sarneel

Janssen

Rip³

et al. 2014

Journal of Applied Ecology

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Summary 1.Restoration activities aiming at increasing vegetation diversity often try to stimulate both dispersal and germination. In wetlands, dispersal and germination are coupled as water and water level fluctuations (WLF) simultaneously influence seed transport and germination conditions (soil moisture). Water regime shifts have been shown to affect vegetation composition. However, the interactions between WLF, dispersal and subsequent germination as drivers of such changes are still poorly understood, especially within the complexity of a field situation. 2. We tested the effect of soil moisture on ten riparian species in the greenhouse and sowed these species on 135 field locations in nine wetlands with recently restored WLF. We used quantile regressions to test the effects of WLF on the window of opportunity for germination from sown seeds and other seeds naturally dispersed to our plots, as well as on community diversity. 3. Soil moisture significantly affected germination both in the greenhouse and in the field. In the complexity of a field situation, a flooding depth just below the soil level, an intermediate flooding duration and a high flooding frequency provided the best opportunities for maximal germination. This was because these conditions enhanced germination from the seed bank as well as increasing germination from dispersed seeds. Seedling diversity showed identical patterns. 4. Other known (i.e., light conditions) and unknown factors played a role as we found low and variable germination, even under optimal conditions. We found evidence that WLF can affect vegetation zonation as flooded seedling communities contained more species with high moisture affinity. 5. Synthesis and applications. Water level fluctuations provide clear windows of opportunity for germination both from the seed bank and from dispersed seeds. Water regime changes are therefore likely to strongly affect recruitment opportunities and subsequent community assembly in riparian ecosystems, for instance through climate change or management. Water level fluctuations can be used as management tool to stimulate plant recruitment and seedling diversity in riparian wetlands.

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Post‐dispersal probability of germination and establishment on the shorelines of slow‐flowing or stagnant water bodies

Cited by 16 publications

References 30 publications

Early plant recruitment stages set the template for the development of vegetation patterns along a hydrological gradient

Early plant recruitment stages set the template for the development of vegetation patterns along a hydrological gradient

Spread pathways of the invasive weed Parthenium hysterophorus L.: The potential for water dispersal

Windows of opportunity for germination of riparian species after restoring water level fluctuations: a field experiment with controlled seed banks

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