A Nine Year Demographic Study of Helenium virginicum (Asteraceae), a Narrow Endemic Seasonal Wetland Plant

Knox, John S.

doi:10.2307/2996611

Cited by 22 publications

(11 citation statements)

References 9 publications

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“…This effect reduces competition from these plants and enables stronger development of B. nana due to the improved light conditions. Similarly, survival of wetland narrow endemics may rely on tolerance to stressful soils, combined with hydroperiod and relaxation of competition (Knox 1997).…”

Section: Discussionmentioning

confidence: 99%

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Demographic variation of dwarf birch (Betula nana) in communities dominated by Ledum palustre and Vaccinium uliginosum

Ejankowski

2010

Biologia

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Abstract:The structure and demographic processes were compared in shrub communities to test the effects of vegetation succession on population growth, fecundity and abundance of the dwarf birch (Betula nana L.), which is a rare and endangered plant species in Poland and a glacial relict in Central Europe. The effects of Ledum palustre L. and Vaccinium uliginosum L. were studied in the Linje nature reserve in Che lmińskie Lake District (northern Poland), in three permanent plots on a peat bog. Vegetative growth and reproduction of B. nana were lower in plant communities dominated by L. palustre and V. uliginosum, than in a reference site. Fecundity was also lower, despite the fact that the percentage share of potentially fertile age groups was similar in all study sites. Mortality of ramets was independent of vegetation, both for juvenile and mature stages. The results confirm that B. nana is intolerant of shade, and it is more abundant in vegetation without competitors. Light limitation can lead to its decline, primarily by a decrease in vegetative growth. Sexual reproduction may be negatively affected by shade, but it plays only small role in population growth. Butterfly larvae can destroy inflorescences, and thus contribute to low effectiveness of sexual reproduction. Increasing density of shrubs and trees in peat bogs can reduce the abundance of dwarf birch, and can lead to the extinction of its local populations.

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Section: Discussionmentioning

confidence: 99%

“…Low light availability also diminishes fertilisation and generative reproduction of many other plants in moist habitats (Falińska 1979b;Knox 1997).…”

Section: Discussionmentioning

confidence: 99%

Demographic variation of dwarf birch (Betula nana) in communities dominated by Ledum palustre and Vaccinium uliginosum

Ejankowski

2010

Biologia

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“…Dominant perennial species in wetlands rarely accumulate persistent seed banks (Hopkins and Parker 1984;Hartman 1988;Hutchings and Russell 1989), except in fluctuating seashore meadows (Jerling 1983). In contrast, many minor marsh species with narrow endemic distribution and with either annual or perennial life-cycles such as Viola persicifolia (Pullin and Woodwell 1987), Howellia aquatilis (Lesica 1992), and Helenium virginicum (Knox 1997) exhibit large permanent seed banks. The persistence of these species in marshes appears to be determined by disturbance, which provides the gaps needed for seed germination and seedling establishment.…”

Section: Discussionmentioning

confidence: 92%

“…The resulting competitive effect reduces the establishment and growth opportunities for minor species (Keddy et al 1998), constituting a great problem for the conservation of threatened plants. Indeed, persistence of wetland rare annuals has been related to the existence of environmental fluctuations (such as hydroperiod and salinity) that enhance plant establishment by creating and maintaining canopy gaps (Pullin and Woodwell 1987;Knox 1997). These species commonly exhibit large permanent seed banks that permit them to escape from the demographic effects of these fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Population biology of Kosteletzkya pentacarpos (Malvaceae) in the Llobregat delta (Catalonia, NE of Spain)

Pino

Roa

2006

Plant Ecol

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Field experiments and wild population monitoring have been performed to study the population biology of the rare long-lived Kosteletzkya pentacarpos (Malvaceae) in the Llobregat delta (Catalonia, NE Spain). Field experiments explored the fate of seeds in soil at different depths, seedling emergence, and seedling survival, growth and flowering with and without canopy cover during the first 2 years of life. They also were used to ascertain the size-related pattern of seedling survivorship and flowering. Field data concerning mortality, growth and fecundity of adult plants were collected yearly in three wild populations for 7-9 years. In old adults (reproducing long before the beginning of the study), ANOVAR tests were performed to compare maximum diameter, total and fertile shoots, and viable seeds per plant between years and populations. New adults (starting flowering the first year of study or in subsequent years) were used to explore, using linear and polynomial regressions, the association of RGR and both total and fertile shoot production with (i) plant size (maximum basal diameter or its logarithm); (ii) plant age (years in adult stage); and (iii) plant age after removing the effect of size and year-to-year fluctuations. In this case, we examined the agerelated pattern of the residuals obtained from the regressions with size and year. The study identified the following main demographic features of K. pentacarpos: (i) transient, shallow soil seed bank; (ii) shade tolerance of seedling emergence; (iii) canopy-facilitation of seedling survival and bolting during the first two years of life; (iv) sizerelated pattern for seedling survivorship but not flowering; (v) exclusive dependence on a fluctuating seed output for reproduction; (vi) rapid adult growth; and (vii) high adult longevity but (viii) rapid depletion of fecundity with age. Seed output was highly constrained by mining insects. The changing size-structure and the decreasing reproductive success of old adults in several populations suggest that K. pentacarpos might undergo a dynamics of population establishment and extinction in the Ricarda marshes. Because of fluctuating reproduction and the lack of a persistent seed bank, the conservation of standing adult populations appears to be a key factor to ensure the persistence of the species.

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“…This may explain why mortality was so high in older ramets at the waterlogged sites. On the other hand, in wetland habitats, light-demanding species may exist due to elimination of competing species (Knox 1997). Probably the potential competitors of B. nana are eliminated by high water table.…”

Section: Discussionmentioning

confidence: 99%

Effect of waterlogging on regeneration in the dwarf birch (Betula nana)

Ejankowski

2008

Biologia

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The aim of this study was to determine the effect of waterlogging on annual regeneration in the dwarf birch (Betula nana L.), and to determine which demographic factors are responsible for the absence of B. nana in the waterlogged parts of a peat-bog. Growth parameters and demographic data were collected from 2001 to 2003 at four sites in the Linje peat bog in the Che lmno Lake District in northern Poland. Three of the sites represented waterlogged open bog communities. The fourth site served as the reference. The density of first-year ramets, annual shoot growth, and the proportion of flowering shoots was significantly lower at the waterlogged sites than at the reference site. No seedlings were found during the course of the study, even though flowering and fruit production took place at the reference site. The flowering shoots were mainly between nine and thirteen years old. Ramets in this age range were found only at the reference site due to high mortality in mature ramets at the waterlogged sites. Mean ramet height was significantly lower at the waterlogged sites than at the reference site, and was strongly correlated with mean ramet age. The distribution of B. nana in peat bogs is limited primarily by two demographic factors: the high mortality rate in older ramets, and the low rate of vegetative reproduction. Another contribution factor is that the proportion of older fertile ramets is low. The effects of fluctuations in the water table on distribution of B. nana are also discussed.

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A Nine Year Demographic Study of Helenium virginicum (Asteraceae), a Narrow Endemic Seasonal Wetland Plant

Cited by 22 publications

References 9 publications

Demographic variation of dwarf birch (Betula nana) in communities dominated by Ledum palustre and Vaccinium uliginosum

Demographic variation of dwarf birch (Betula nana) in communities dominated by Ledum palustre and Vaccinium uliginosum

Population biology of Kosteletzkya pentacarpos (Malvaceae) in the Llobregat delta (Catalonia, NE of Spain)

Effect of waterlogging on regeneration in the dwarf birch (Betula nana)

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