maintained exclusively by high tide, and salts flats which both offer habitats for
halophile species, and the lower course of the Dragonja river with its river mouth
and freshwater as well as brackish riparian habitats along the banks. S ˇ kocjan inlet
was renatured some years ago and here, too, different Natura 2000 habitats
developed. In some years A. squamatus was found to be very abundant, even
exceeding the abundance of the native halophile vegetation (Glasnovic ´ and Fis ˇer
Pec ˇnikar 2010). The occurrence of A. squamatus is especially dense within and
around the port of Koper, possibly the source of the arrival of the species on the
Slovenian coast.
Species-specific empirical data are important for individual-based modelling of
future changes of biodiversity; in particular, data about dispersal and life history
trade-offs might improve model realism (Botkin et al. 2007). Additionally,
knowledge about preferred environmental conditions helps to improve nichebased models because it allows forecasting of the persistence and distribution of
species (Botkin et al. 2007). Thus, knowledge of a species’ reproductive success is
needed for better understanding of its invasive potential, while on the other hand,
micro-scale habitat properties along with biotic interactions also influence trends in
the richness and abundance observed in alien species (Aguiar et al. 2006). This is
why we estimated the reproductive potential of A. squamatus by measuring seed
production of individual plants in relation to plant height and soil properties,
especially soil salinity and humidity. Additionally, we tested the seeds for their
germination characteristics.
19.3 Determining the Reproductive Potential
and Habitat Characteristics
In evaluating the reproductive potential of A. squamatus plants, we recognised five
categories of plant height: 1 – below 50 cm; 2 – from 50 to 70 cm; 3 – from 70 to
110 cm; 4 – from 110 to 140 cm; and 5 – from 140 to 170 cm. The potential
reproductive success of A. squamatus plants was estimated by counting the number
of flower heads for plants belonging to each category, as well as seed number per
single flower head. The data obtained were used in making a calculated estimation
of the total seed number for an individual plant. Subsequently, we tested the seeds
for their germination rate in laboratory conditions. We collected ripe seeds in the
field in October 2011; these were dry-stored until the beginning of the experiment.
Twenty seeds were allowed to germinate untreated on filter paper, watered with
distilled water for 31 days. Observations were performed every 2 days, at which
point germinated seeds were counted and removed.
Soil samples collected from plots where A. squamatus was absent (0) or present
(1), were analysed for P, K, organic matter, C, total N, C:N content, Zn and
pH. Additionally, we measured the salinity and humidity of the soil samples.
Where present, the A. squamatus plants were categorised into different height
classes (a – 50 cm or less, b – between 50 and 100 cm, and c – above 100 cm).
19 Reproduction Biology of an Alien Invasive Plant: A Case of. . .
281
halophile species, and the lower course of the Dragonja river with its river mouth
and freshwater as well as brackish riparian habitats along the banks. S ˇ kocjan inlet
was renatured some years ago and here, too, different Natura 2000 habitats
developed. In some years A. squamatus was found to be very abundant, even
exceeding the abundance of the native halophile vegetation (Glasnovic ´ and Fis ˇer
Pec ˇnikar 2010). The occurrence of A. squamatus is especially dense within and
around the port of Koper, possibly the source of the arrival of the species on the
Slovenian coast.
Species-specific empirical data are important for individual-based modelling of
future changes of biodiversity; in particular, data about dispersal and life history
trade-offs might improve model realism (Botkin et al. 2007). Additionally,
knowledge about preferred environmental conditions helps to improve nichebased models because it allows forecasting of the persistence and distribution of
species (Botkin et al. 2007). Thus, knowledge of a species’ reproductive success is
needed for better understanding of its invasive potential, while on the other hand,
micro-scale habitat properties along with biotic interactions also influence trends in
the richness and abundance observed in alien species (Aguiar et al. 2006). This is
why we estimated the reproductive potential of A. squamatus by measuring seed
production of individual plants in relation to plant height and soil properties,
especially soil salinity and humidity. Additionally, we tested the seeds for their
germination characteristics.
19.3 Determining the Reproductive Potential
and Habitat Characteristics
In evaluating the reproductive potential of A. squamatus plants, we recognised five
categories of plant height: 1 – below 50 cm; 2 – from 50 to 70 cm; 3 – from 70 to
110 cm; 4 – from 110 to 140 cm; and 5 – from 140 to 170 cm. The potential
reproductive success of A. squamatus plants was estimated by counting the number
of flower heads for plants belonging to each category, as well as seed number per
single flower head. The data obtained were used in making a calculated estimation
of the total seed number for an individual plant. Subsequently, we tested the seeds
for their germination rate in laboratory conditions. We collected ripe seeds in the
field in October 2011; these were dry-stored until the beginning of the experiment.
Twenty seeds were allowed to germinate untreated on filter paper, watered with
distilled water for 31 days. Observations were performed every 2 days, at which
point germinated seeds were counted and removed.
Soil samples collected from plots where A. squamatus was absent (0) or present
(1), were analysed for P, K, organic matter, C, total N, C:N content, Zn and
pH. Additionally, we measured the salinity and humidity of the soil samples.
Where present, the A. squamatus plants were categorised into different height
classes (a – 50 cm or less, b – between 50 and 100 cm, and c – above 100 cm).
19 Reproduction Biology of an Alien Invasive Plant: A Case of. . .
281