Seed bank of an invasive alien, Heracleum mantegazzianum, and its seasonal dynamics

Abstract

The seed bank of Heracleum mantegazzianum, native to the western Caucasus and invasive in Europe, was studied in the Slavkovský les Protected Landscape Area, the Czech Republic, during the course of two growing seasons. In each of seven study sites with dominating stands of the species, soil samples were taken in October (after the fruit release), April (before germination) and June–July (before the fruit release). Ten samples were taken from each site using a soil hand bore, 4.6 cm in diameter. Seeds elutriated from the samples were immediately germinated in laboratory conditions (10°C, 12 h light/12 h dark); those that germinated during 1 month were considered as non-dormant. Non-germinated but viable seeds, tested for viability by tetrazolium, were considered as dormant. The number of dead seeds was also recorded. The total number of seeds significantly increased with mean density of flowering plants at a site. Of the total variation in seed-bank size, about four-fifths were attributed to that among sites, and one-fifth to that within sites. The number and proportion of living seeds differed significantly between years in summer, but not in autumn and spring. Total number and the numbers of dormant, non-dormant, living and dead seeds significantly differed among the autumn, spring and summer samples. The percentage of living seeds in the total seed bank decreased from 56% in autumn to 42% in spring to 15% in summer. The percentage of non-dormant seeds among those living was 0.3% in autumn, it increased to 87.5% in the spring sample, and decreased to 3% in summer. Pooled across all sites, the average seed numbers (expressed per m2) were 6719±4119 (mean±SD) in autumn, 4907±2278 in spring and 1301±1036 in summer for the total number of seeds, and 3759±2906, 2044±1198 and 192±165, respectively, for living seeds. The majority of seeds (95%) were concentrated in the upper 5 cm soil layer. However, some seeds were present in lower soil layers, which indicates a short-term persistent seed bank. The present data are the first quantitative estimate of the seed bank in H. mantegazzianum, and show that the reproductive potential of the species is enormous, which seems to be a crucial feature of its invasion success.

Timing and extent of tissue removal affect reproduction characteristics of an invasive species Heracleum mantegazzianum

“…This makes it a species of special conservation concern (Pyšek et al 2004a) and subject to various control measures. Since the species' population dynamics depend entirely on reproduction by seed (Tiley et al 1996;Moravcová et al 2005;Krinke et al 2005), this phase of its life history is a convenient target of mechanical control.…”

Evaluación interanual de las estrategias regenerativas de la especie exótica invasora Gleditsia triacanthos en relación a la nativa Acacia aroma en el bosque chaqueño serrano de Córdoba (Argentina)

“…Asimismo, las variaciones en la producción de frutos repercutirían en otras variables del ciclo reproductivo de las especies, pudiendo generar, por ejemplo, variaciones en la densidad de semillas del banco o de plántulas establecidas. A su vez, la variabilidad interanual en estas últimas variables regenerativas podría deberse a otros factores como cambios en la germinabilidad de las semillas, variaciones anuales en la comunidad de herbívoros o en hongos, microbios y otros depredadores que se encuentren en el suelo (Rudgers y Hoeksema 2003, Krinke et al 2005). Además, factores abióticos, lluvias o fuegos particulares de cada temporada, podrían influir en la densidad de semillas o plántulas (Krinke et al 2005).…”

The Biology of Invasive Alien Plants in Canada. 4. Heracleum mantegazzianum Sommier & Levier

“…Although no light requirements have been demonstrated for germination , best emergence in the field has been observed in the open or under light vegetative cover in the United Kingdom (Tiley et al 1996). Most seeds geminate from a depth of less than 5 cm, although emergence from 10 cm has been observed (Krinke et al 2005;Moravcová et al 2005). Seeds will rot in flooded soil.…”

“…(c) Seed Banks, Seed Viability and Germination -A seed bank study at seven sites in the Czech Republic by Krinke et al (2005) found that the numbers of seeds in the seed bank was directly related to plant density and that the numbers and proportion of viable seeds at any one site varied between years. Pooled results showed a mean total soil seed population per m 2 of 6719 ± 4119 in autumn, 4907 ± 2278 in spring and 1301 ± 1036 in summer, 95% of which were present in the upper 5 cm.…”

“…Results of germination tests in H. mantegazzianum have varied considerably but general conclusions are that seeds are dormant or require a long after-ripening period after being shed. Krinke et al (2005) identified dormant seeds in Czech populations by testing the viability of non-germinating seeds with tetrazolium. Seeds that were artificially dried and stored indoors often failed to germinate, but seed stored outdoors throughout the winter germinated well (Tiley et al 1996).…”