Effects of competition from introduced plants on establishment, survival, growth and reproduction of the rare plant Solidago shortii (Asteraceae).

摘要

Field and glasshouse studies in Kentucky, USA, were conducted to investigate the effects of introduced species on endangered S. shortii. Plots with S. shortii were kept free of other vegetation (mostly Coronilla varia) and litter between May 1993 and September 1997. In treatment plots, S. shortii flowering ramet numbers increased significantly between 1992 and 1993, and remained nearly constant between 1993 and 1996. In control plots, flowering ramet numbers were significantly lower than those in treatment plots from 1993 to 1996. The number of non-flowering ramets progressively increased from 1993 to 1996 in treatment plots. S. shortii seedlings established in treatment plots. Of 1322 seedlings marked in May 1994, 3% were alive and～0.4% of themhad flowered by September 1997. At the end of 4 growing seasons, 36, 23, 18, 10, 8 and 5% of the 39 surviving plants were in 3-10, 11-20, 21-30, 31-40, 41-50 and >50 cm height classes, respectively. In a replacement series experiment, S. shortii and Festuca arundinacea competed for the same resources. Relative yield (RY) of S. shortii was significantly lower than expected, whereas F. arundinacea RY was significantly greater. The aggressivity value of S. shortii was significantly lower than that of F. arundinacea. Significantly fewer individuals of S. shortii flowered under inter- than under intra-specific competition. In conclusion, seedling establishment and vigour of S. shortii is greatest in the absence of competitors.