Dynamics of Yellow Starthistle (Centaurea solstitialis) Achenes in Field and Laboratory

Abstract

Studies were conducted to compare changes in germinability and/or viability of yellow starthistle achenes buried (in packets) in soil or stored dry in the laboratory, and to determine the rate of achene depletion from a soil seed bank. In one study, after 72 mo, 0 to 96% germinable achenes remained in packets buried 5 cm deep, and a mean above 99% after dry storage. In another study, total live (germinable plus viable) achenes declined from 100% at harvest to 77.6% after 24 mo of burial. Germinable pappus-bearing achenes remaining in packets increased with depth of burial. After 12 mo of burial, maximum survival of achenes occurred at depths of 5 cm or more. The density of yellow starthistle achenes and seedlings in a natural soil seed bank declined, when achene rain was prevented, to 3.9 and 1.1% of initial density, respectively, after 36 mo. Decline was attributed primarily to seedling emergence and achene death. Achene density in the upper 2.5 cm of soil appeared to be a good predictor of seedling emergence after autumn rains.

Expansion history and environmental suitability shape effective population size in a plant invasion

“…Reproduction is by seed only (there is no clonal reproduction), and seeds are either unadorned (outer florets) or have a small (2 mm) bristle‐like pappus that appears to be better adapted for animal (including human) dispersal than for wind dispersal (Gerlach, ; Roche, ; Sun & Ritland, ). Over 80% of seeds germinate within the first year, and while seeds can remain viable within the soil for up to 10 years, most natural seed banks appear to be depleted in three years without new input (Benefield, DiTomaso, Kyser, & Tschohl, ; Callihan, Prather, & Northam, ; Joley, Maddox, Supkoff, & Mayfield, ).…”

Does Superior Competitive Ability Explain Yellow Starthistle's (Centaurea solstitialis) Successful Invasion of Annual Grasslands in California?

“…The ability of resident wild oat in a given habitat to resist invasion by yellow starthistle is unknown. The purposes of this study were (1) to test the hypothesis that yellow starthistle was a strong competitor relative to the annual grass, wild oat (and thus able to displace resident species) (Balciunas and Villegas 2001;Benefield et al 1999Benefield et al , 2001DiTomaso et al 2003;Joley et al 1992;Lass et al 1996;Shinn and Thill 2002;Thomsen et al 1996) and (2) to test the hypothesis that soil moisture levels differ (according to previously observed patterns with other species) when these species are grown alone or in combination with each other. To that end we grew both species in mixtures and monocultures in outdoor experiments in Davis, CA, and measured plant performance as well as soil moisture dynamics.…”

“…DiTomaso et al (1999) reported reduced native plant diversity in the presence of dense yellow starthistle cover. Some researchers have indicated that yellow starthistle competitively excludes resident species, but in many cases these reports have not included data that support these statements (Balciunas and Villegas 2001;Benefield et al 1999Benefield et al , 2001DiTomaso et al 2003;Joley et al 1992;Lass et al 1996;Shinn and Thill 2002;Thomsen et al 1996). …”

Widespread seed limitation affects plant density but not population trajectory in the invasive plant Centaurea solstitialis

“…solstitialis' seedbank is short-lived in California. The majority of its seeds germinate or die in the first year (Benefield et al 2001;Joley et al 1992;Garren and Strauss 2009). Benefield et al (2001) found that within a year of dispersing from the maternal plant, only 7% of the seeds remain alive in the soil.…”