PARENT SESSION
Poster Session 20: Invasive Species
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Growth and germination responses of a vigorous invasive plant, Ambrosia trifida, to some natural and man-made conditions in Japan.
Ishikawa, Shin-Ichi*,1, Nakajima, Jun2, Kayashima, Kazuma1, 1 Faculty of Social and Information Studies, Maebashi, Gunma, JAPAN2 Niigata City Office, Niiata, Niigata, JAPAN
ABSTRACT- Growth and germination responses of an invasive annual plant, Ambrosia trifida , which can be commonly seen in Japanese riparian area, to temperature, disturbance, nitrogen were investigate to clarify why this species have invaded so large area. Field research along the upper stream of Tone River revealed that there are 31 large populations established already within Gunma Prefecture and, at the most, over 17 billions of seeds were produced annually in each of the populations. In situ growth analysis proposed that the relative growth rate (RGR) in the main growth period is independent of the air temperatures at the sites and the individual biomass and seed production depend on the germination day. Growth experiments with different nitrogen conditions revealed that the seedlings came from the site with higher soil ammonia/nitrate ratio (A/N) showed a high RGR in high A/N treatment comparable to that in low A/N, whereas those from the site with lower A/N had low RGR in high A/N treatment. Filed fire experiment revealed that the winter artificial burning of the invaded site enhanced soil nitrate concentration and soil temperature in spring, and caused faster germination and higher biomass, comparing to those in un-burnt site. Seed germination at 10/7 C (day/night) was always higher than that at any higher temperature conditions, and this tendency was more clear in seeds sampled in sites under colder climate. These results suggest that A. trifida may have been invading areas with higher soil nitrate concentration, high light conditions and better temperature conditions for germination, which are caused by human disturbance.
Key words: Ambrosia trifida, growth analysis, seed germination, nitrogen