Role of temperature and light in the germination ecology of buried seeds of weedy species of disturbed forests. I. Lobelia inflata

Lobelia inflata L. is a weedy species that may be abundant in disturbed forest sites. Temperature and light requirements for germination were determined at 12-h daily thermoperiods of 15:6, 20:10, 25:15, 30:15, and 35:20 °C for seeds exhumed after 0–28 months (September 1987 to February 1990) of burial in soil at near-natural temperatures. At maturity in autumn 1987, 2–15% of the seeds germinated after 15 days incubation at the five thermoperiods in light but 0% germinated in darkness. By January 1988, 68–100% of the seeds germinated in light at all thermoperiods except 15:6 °C. Germination at 20:10, 25:15, and 30:15 °C did not decrease to below 60% during the remainder of the study, and germination at 35:20 °C was less than 60% only four times. Germination at 15:6 °C was erratic with peaks in spring 1988, and in spring to early summer and autumn 1989. Regardless of the season in which seeds were exhumed, they did not germinate in darkness. In a laboratory study, stratification at 5 °C broke dormancy but did not substitute for the light requirement. Seeds of L. inflata have the potential to form long-lived seed banks, and buried seeds can germinate at any time during the growing season if exposed to light. Key words: seed dormancy, seed germination, buried seeds, Lobelia inflata, stratification.

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The role of soil temperature and seed dormancy in the creation and maintenance of persistent seed banks of Nassella trichotoma (serrated tussock) on the Northern Tablelands of New South Wales

The Rangeland Journal ◽

10.1071/rj20008 ◽

2020 ◽

Vol 42 (2) ◽

pp. 85

Author(s):

Annemieke Ruttledge ◽

Ralph D. B. Whalley ◽

Gregory Falzon ◽

David Backhouse ◽

Brian M. Sindel

Keyword(s):

Seed Bank ◽

New South ◽

Soil Seed Bank ◽

Seed Banks ◽

Early Summer ◽

Secondary Dormancy ◽

South Wales ◽

The Creation ◽

Persistent Soil Seed Bank

A large and persistent soil seed bank characterises many important grass weeds, including Nassella trichotoma (Nees) Hack. ex Arechav. (serrated tussock), a major weed in Australia and other countries. In the present study we examined the effects of constant and alternating temperatures in regulating primary and secondary dormancy and the creation and maintenance of its soil seed bank in northern NSW, Australia. One-month-old seeds were stored at 4, 25°C, 40/10°C and 40°C, in a laboratory, and germination tests were conducted every two weeks. Few seeds germinated following storage at 4°C, compared with seeds stored at 25°C, 40/10°C and 40°C. Nylon bags containing freshly harvested seeds were buried among N. trichotoma stands in early summer, and germination tests conducted following exhumation after each season over the next 12 months. Seeds buried over summer and summer plus autumn had higher germination than seeds buried over summer plus autumn plus winter, but germination increased again in the subsequent spring. Seeds stored for zero, three, six and 12 months at laboratory temperatures were placed on a thermogradient plate with 81 temperature combinations, followed by incubation at constant 25°C of un-germinated seeds. Constant high or low temperatures prolonged primary dormancy or induced secondary dormancy whereas alternating temperatures tended to break dormancy. Few temperature combinations resulted in more than 80% germination.

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Germination requirements of Oenothera biennis seeds during burial under natural seasonal temperature cycles

Canadian Journal of Botany ◽

10.1139/b94-098 ◽

1994 ◽

Vol 72 (6) ◽

pp. 779-782 ◽

Cited By ~ 26

Author(s):

Carol C. Baskin ◽

Jerry M. Baskin

Keyword(s):

Seed Banks ◽

Late Winter ◽

Seasonal Temperature ◽

Oenothera Biennis ◽

Light Requirement ◽

Term Survival ◽

Temperature Changes ◽

Buried Seeds ◽

Dormancy Cycles

Buried seeds of Oenothera biennis, which have the potential to form long-lived seed banks, were investigated to determine whether or not they (i) undergo seasonal changes in their dormancy states and (ii) require light for germination. Seeds were buried in soil and exposed to natural seasonal temperature changes. Samples of seeds were exhumed at monthly intervals for 31 months and tested for germination in light and darkness at 12-h daily thermoperiods of 15:6, 20:10, 25:15, 30:15, and 35:20 °C. At maturity in autumn, seeds germinated to 84–95% in light at 30:15 and 35:20 °C, but to 0–69% at other test conditions. By late winter, seeds germinated to 95–100% at the five thermoperiods in light and in darkness. In summer and autumn, germination in light decreased at 15:6 °C, and in darkness it dropped to 0% at 15:6 °C and decreased at 20:10, 25:15, 30:15, and 35:20 °C. Following the second winter of burial, seeds germinated to near 100% at all thermoperiods in light and darkness. Thus, seeds exhibited an annual nondormancy – conditional dormancy cycle, being nondormant from midwinter to late spring and conditionally dormant in summer and autumn. Oenothera biennis is 1 of 10 species whose seeds live for 39–40 years or longer in soil and also have an annual conditional dormancy – nondormancy cycle. Seeds of six of these species, including O. biennis, can germinate in darkness in spring or summer at simulated habitat temperatures. Therefore, a light requirement for germination is not necessarily a prerequisite for long-term survival of buried seeds, and something other than darkness prevents germination of seeds of some species buried in soil. Key words: seed banks, buried seeds, germination, dormancy cycles, light requirement, Oenothera.

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Role of temperature and light in the germination ecology of buried seeds of weedy species of disturbed forests. II. Erechtites hieracifolia

Canadian Journal of Botany ◽

10.1139/b96-240 ◽

1996 ◽

Vol 74 (12) ◽

pp. 2002-2005 ◽

Cited By ~ 16

Author(s):

Carol C. Baskin ◽

Jerry M. Baskin

Keyword(s):

Seed Bank ◽

Full Range ◽

Soil Disturbance ◽

Seasonal Temperature ◽

Temperature Changes ◽

Test Conditions ◽

Buried Seeds ◽

Weedy Species ◽

Dormancy Cycles

At maturity in September, about half the seeds (achenes) of Erechtites hieracifolia (Asteraceae) collected in Kentucky were dormant (did not germinate at any test condition), whereas the others were conditionally dormant (germinated only at a narrow range of test conditions). Seeds sown on top of soil in an unheated greenhouse in September failed to germinate in autumn because temperatures were below those required for germination; however, they germinated at comparable temperatures the following spring. Seeds buried in soil in September 1987 and exposed to natural seasonal temperature changes were nondormant (germinated over full range of test conditions) by April 1988, but they entered conditional dormancy by October 1988. Each October through 1995, exhumed seeds exhibited conditional dormancy. Since 89% of the seeds were viable after 8 years of burial, it appears that although seeds of this species are wind dispersed, they also have the potential to form a long-lived seed bank. Thus, soil disturbance at any time from May to September could result in establishment of plants from seeds in the seed bank. Keywords: seed dormancy, Asteraceae, dormancy cycles, buried seeds, light.

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Which factors influence the density of birch (Betula pendula Roth) seeds in soil seed banks in temperate woodlands?

European Journal of Forest Research ◽

10.1007/s10342-021-01411-x ◽

2021 ◽

Author(s):

Katharina Tiebel

Keyword(s):

Soil Seed Bank ◽

Seedling Emergence ◽

Soil Layer ◽

Ground Cover ◽

Seed Banks ◽

Soil Seed Banks ◽

Seed Sources ◽

Forest Sites ◽

Spruce Stands ◽

Disturbed Forest

AbstractThe natural regeneration of disturbed forest sites is becoming increasingly important due to climate change. Following disturbance events affecting large areas seed trees are often absent from the site, and regeneration solely by means of seed rain may not be successful. In these situations, soil seed banks are an important driver of the regeneration and reforestation of forest sites. The aim of the study was to determine the birch seed density in the soil of birch stands, spruce–birch stands and spruce stands dependent upon the number of seed trees (stands) and upon varying degrees of ground cover using the ‘seedling emergence method.’ The study revealed a significant link between the quantity of germinated birch seedlings in soil samples and the presence of seed sources. Seedling densities of birch in the different stand categories reached 2644–6414 seedlings per m2 [n m−2] in birch stands, 392–759 n m−2 in spruce–birch stands and 25–122 n m−2 in pure spruce stands. The density of germinated birch seedlings was also negatively affected by the soil layer. In all stand types, the factors humus thickness, litter cover, moss cover and herb cover had no significant influence on the amount of birch seedlings. Successful rapid regeneration of disturbed sites by means of the birch soil seed bank is guaranteed in cases where birch stands, or at least birch seed trees, were present before the event. The influence of ground cover on the regeneration potential of birch from the soil is negligible.

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The composition and diversity of natural regeneration of tree species in gaps under different intensities of forest disturbance

Journal of Forestry Research ◽

10.1007/s11676-020-01269-6 ◽

2021 ◽

Author(s):

Maame Esi Hammond ◽

Radek Pokorný ◽

Daniel Okae-Anti ◽

Augustine Gyedu ◽

Irene Otwuwa Obeng

Keyword(s):

Tree Species ◽

Natural Regeneration ◽

Forest Disturbance ◽

Forest Site ◽

Gap Formation ◽

Tree Species Composition ◽

Forest Sites ◽

Significant Difference ◽

Shade Tolerant Species ◽

Disturbed Forest

AbstractThe positive ecological interaction between gap formation and natural regeneration has been examined but little research has been carried out on the effects of gaps on natural regeneration in forests under different intensities of disturbance. This study evaluates the composition, diversity, regeneration density and abundance of natural regeneration of tree species in gaps in undisturbed, intermittently disturbed, and disturbed forest sites. Bia Tano Forest Reserve in Ghana was the study area and three gaps each were selected in the three forest site categories. Ten circular subsampling areas of 1 m2 were delineated at 2 m spacing along north, south, east, and west transects within individual gaps. Data on natural regeneration < 350 cm height were gathered. The results show that the intensity of disturbance was disproportional to gap size. Species diversity differed significantly between undisturbed and disturbed sites and, also between intermittently disturbed and disturbed sites for Simpson’s (1-D), Equitability (J), and Berger–Parker (B–P) indices. However, there was no significant difference among forest sites for Shannon diversity (H) and Margalef richness (MI) indices. Tree species composition on the sites differed. Regeneration density on the disturbed site was significantly higher than on the two other sites. Greater abundance and density of shade-dependent species on all sites identified them as opportunistic replacements of gap-dependent pioneers. Pioneer species giving way to shade tolerant species is a natural process, thus make them worst variant in gap regeneration.

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Light Requirements of Buried Seeds

Nature ◽

10.1038/213600a0 ◽

1967 ◽

Vol 213 (5076) ◽

pp. 600-601 ◽

Cited By ~ 46

Author(s):

G. WESSON ◽

P. F. WAREING

Keyword(s):

Light Requirements ◽

Buried Seeds

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Seed mass and light requirements for regeneration in Southeast Asian rain forest

Canadian Journal of Botany ◽

10.1139/b95-090 ◽

1995 ◽

Vol 73 (6) ◽

pp. 817-826 ◽

Cited By ~ 59

Author(s):

D. J. Metcalfe ◽

P. J. Grubb

Keyword(s):

Phylogenetic Analysis ◽

Rain Forest ◽

Secondary Forest ◽

Seed Mass ◽

Primary Forest ◽

Secondary Forests ◽

Light Requirement ◽

Lowland Rain Forest ◽

Light Requirements ◽

Shade Tolerant Species

Seed mass values are given for 140 species of primary lowland rain forest and associated secondary forests in Singapore. Among shade-tolerant species of primary forest there is a trend for a decrease in mean seed mass with tall trees > woody climbers > small trees > shrubs > herbs; the differences between tall trees and small trees or shrubs or herbs, and between herbs and small trees or woody climbers are significant. There are a few light-demanding herbs or shrubs in the primary forest; among small trees, light demanders have significantly lower seed mass values than shade tolerators. In 9 out of 13 comparisons within taxa including both shade tolerants and light demanders the former had appreciably larger seeds than the latter. Two out of 13 comparisons involved very small seeded shade tolerators, and one a notably large-seed light demander. Many shade-tolerant herbs, shrubs, and trees have seed mass values much smaller than those of trees of secondary forest conventionally regarded as small seeded, and exploit moist, litter-free sites, e.g., steep microslopes. The trees of secondary forests on degraded soils do not differ significantly in seed mass from those on nondegraded soils. Key words: seed mass, light requirement, regeneration, tropical rain forest, phylogenetic analysis.

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Seasonal variation of mono- and sesquiterpene emission rates of Scots pine

Biogeosciences ◽

10.5194/bg-3-93-2006 ◽

2006 ◽

Vol 3 (1) ◽

pp. 93-101 ◽

Cited By ~ 171

Author(s):

H. Hakola ◽

V. Tarvainen ◽

J. Bäck ◽

H. Ranta ◽

B. Bonn ◽

...

Keyword(s):

Seasonal Variation ◽

Scots Pine ◽

Early Summer ◽

Emission Rates ◽

High Concentration ◽

Temperature Dependent ◽

Emission Pattern ◽

Defensive Role ◽

Monoterpene Emission

Abstract. The seasonal variation of mono-and sesquiterpene emission rates of Scots pine was measured from April to October in 2004. The emission rates were measured daily in the afternoons with the exception of weekends. Emissions were measured from two branches; one of them was debudded in May (branch A), while the other was allowed to grow new needles (branch B). The monoterpene emission pattern remained almost constant throughout the measurement period, Δ3-carene being the dominant monoterpene (50-70% of the VOC emission). The standard monoterpene emission potential (30°C) was highest during early summer in June (the average of the two branches 1.35 µg g-1h-1) and lowest during early autumn in September (the average of the two branches 0.20 µg g-1h-1. The monoterpene emission potential of branch A remained low also during October, whereas the emission potential of branch B was very high in October. The sesquiterpenes were mainly emitted during mid summer, the dominant sesquiterpene being β-caryophyllene. Branch A had a higher sesquiterpene emission potential than branch B and the emission maximum occurred concomitant with the high concentration of airborne pathogen spores suggesting a potential defensive role of the sesquiterpene emissions. The sesquiterpene emissions were well correlated with linalool and 1,8-cineol emissions, but not with monoterpenes. Sesquiterpene and 1,8-cineol emissions were equally well described by the temperature dependent and the temperature and light dependent algorithms. This is due to the saturation of the light algorithm as the measurements were always conducted during high light conditions.

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