DYNAMICS OF SEED BANK AND SURVIVORSHIP OF MEADOW SALSIFY (TRAGOPOGON PRATENSIS) POPULATIONS

Seasonal changes in germination behaviour of meadow salsify seeds buri ed at different depths, and survivorship of seed and plant populations were investigated. Freshly matured seeds were mixed with sterilized s oil, placed into nylon mesh bags, and buried at three soil depths in a meadow salsify-infested rangeland. Two germination peaks were observe d: one in the fall, 2 to 3 mo after burial, and a second the following spring. Burial depth affected seed dormancy. The number of seeds with enforced dormancy, and innate or induced dormancy, increased with bur ial depth in the 1989 cohort, and the number with enforced dormancy in creased in the 1990 cohort. Burial depth also affected seed survivorsh ip. The survivorship curves for 1989 and 1990 seed cohorts were not di fferent as indicated by the Logrank test. The seed population was near ly depleted after 9 to 10 mo of burial; less than 3% of the buried see ds remained viable after 13 mo. About 50% of the plants monitored in a natural meadow salsify population in 1990 died before winter, and an additional 35% died during winter. The mortality of the remaining plan ts during the second growing season was very low Only 12% of the 1990 cohort remained in October 1991. Mortality of meadow salsify plants wa s density-independent.