Factors affecting the establishment of Cytisus scoparius in southern France: implications for managing both native and exotic populations.

Abstract

The ecology of C. scoparius (broom) was studied between 1993 and 1997 in southern France to investigate how it can become an invasive weed in its native range. The proportion of seed bank germinating each year was greatest in disturbed plots and was correlated with the March rainfall. The seed bank declined at a rate of ∼50% per year when fresh seed rain was excluded. No seedlings in undisturbed plots survived the first summer, while >40% survived the first summer and ∼14% survived to flowering age in plots that were initially cultivated. Inter- and intraspecific competition did not significantly affect seedling survival on cultivated plots. However, after 27 months, 10% of plants without competition set seed, compared to 0.3% of plants experiencing interspecific competition. C. scoparius was generally free from pest attack. Applications of insecticide, molluscicide or fungicide did not significantly affect seedling survival, growth or minimum age of reproduction on cultivated plots. It is concluded that management strategies should minimize disturbance to competing vegetation, which can inhibit germination and smother emerging seedlings. In many circumstances strategies that target the seed bank, such as burning, are not expected to work.

Key words

• agricultural entomology
• biological competition
• cultural control
• disturbed land
• establishment
• fungicides
• insecticides
• interspecific competition
• intraspecific competition
• introduced species
• invasion
• invasive species
• molluscicides
• natural enemies
• plant competition
• population dynamics
• seed banks
• seed germination
• vegetation management
• weed control
• weeds
• woody plants
• woody weeds