A comparative study of the seed germination biology of a narrow endemic and two geographically-widespread species of Solidago (Asteraceae). 6. Seed bank

Seeds of the geographically-widespread Solidago altissima and S. nemoralis and the narrow-endemic S. shortii were buried in pots of soil and placed in a glasshouse without temperature control. After 0.3-4.3 years of burial, some seeds (21-60%) of all three species were viable and they germinated to 75-100% during 2 weeks of incubation in light at 30/15°C. Soil samples collected from several population sites of S. altissima, S. nemoralis and S. shortii were placed in the glasshouse and monitored for seedling emergence. During the first, second, third, fourth, fifth and sixth springs, the number of S. altissima seedlings m(-2) emerging was 108-1080, 8-494, 0-520, 0-69, 0-6 and 3, respectively, of S. nemoralis was 108-1122, 17-667, 0-42, 0-6, 0 and 0, respectively, and of S. shortii was 61-1753, 0-25, 0-6, 0, 0 and 0, respectively. More seedlings emerged from disturbed than from non-disturbed soil, but the differences were not significant. Thus, although some seeds of all three species buried in pots remained viable in soil throughout the 4.3-year burial period, longevity was greater and size of seed bank larger in field-collected soil samples containing seeds of the geographically-widespread species than in those containing seeds of the narrow endemic. Although 34 studies have reported seeds of 17 species of Solidago present in soil seed banks, the present study is the first to show conclusively that Solidago can form a persistent seed bank.