Germination in Baltic coastal wetland meadows: similarities and differences between vegetation and seed bank

Abstract

The abundance and variety of seedlings in Baltic coastal grasslands was studied in cattle grazed and ungrazed areas in seashore and delta on the western coast of Finland. The vegetation, seed bank and environmental conditions of the same sites were also studied. Altogether 4609 seedlings were observed in 79 field plots (20 cm× 20 cm) making an average of 1458.54 seedlings/m2. The majority of the seedlings were dicots (67.5%) and perennials (96.8%). Altogether 44 species and an average of 4.14 species per plot were identified as seedlings. The most abundant taxon, Carex formed 23.2% of all the seedlings observed in the field. In the delta the seedling density was two times that found at the seashore. Also, the numbers of species of seedlings per plot were significantly higher in the delta than in the seashore, but in total, more species germinated from the seashore than from the delta even though the number of plots was higher in the delta (n = 51) than in the seashore (n = 28). The numbers of species and seedlings per plot were smaller in grazed sites than in ungrazed ones similar to the pattern earlier reported concerning the mature vegetation and seed bank. The mean numbers of seedlings were the highest at lower geolittoral plots (about 20 cm elevation), where the seed bank was also densest. About 60.0% of the mature species in the plots were also detected as seedlings and 91.4% of the seedling species were found in the mature vegetation of the plots. The number of seedlings was positively correlated with the cover of mature vegetation giving support to the nurse effect theory. Seedling numbers were negatively correlated with the abundance of litter indicating that litter restricts germination because it is a mechanical barrier but also decreases the amount of light. The number of seedlings and species, both in total and per unit area, were greater in the seed bank than in the field seedling population. The seedling population was more similar to the mature vegetation than to the seed bank.