Plant traits and temporal scale: evidence from a 5-year invasion experiment using native species

1 A long-term experiment was established in 1990 in which seeds of 54 native species, not originally present at the site, were sown into a fertility x disturbance matrix established in unproductive limestone grassland at the Buxton Climate Change Impacts Laboratory (BCCIL). The objective was to examine the roles of productivity and disturbance as major factors controlling the invasibility of plant communities, and to identify the functional characteristics of successful invaders in response to different types of invasion opportunity. The results of the first 2 years of the study have already been published. 2 After 2 years, invasion was strongly promoted by disturbance and less so by increased fertility. Three years later the cover of invaders had declined over most of the matrix, and the greatest cover of sown species was where the highest levels of fertility and disturbance coincided. However, no part of the fertility-disturbance matrix was immune to invasion and the area of the matrix occupied by each of the sown species that successfully established was unique. Abundance of invaders was reduced by low soil pH. 3 The identity and distribution of the successful invaders changed as the early stages of invasion gave way to a later stage of consolidation. After 2 years regenerative traits (seed mass and germination characteristics) were the best predictors of success. After 5 years these traits were unrelated to success of the invaders, the most successful invaders were perennial grasses, and no single trait was a good predictor of invasiveness. 4 Our results are consistent with the hypothesis that invasions are promoted by an increase in the availability of resources, either through addition of extra resources or a reduction in their use by the resident vegetation.