A ten-year seed bank study of old field succession in central New Jersey

Seed bank and vegetation dynamics of a newly abandoned agricultural field were studied for a decade (1984-1994). Seed bank densities ranged from 3540 m(-2) (yr 1) to 50,182 m(-2) (yr 3), and species richness from 26 (yr 1) to 39 species (yr 7). Over the decade 55 taxa occurred in seed bank samples and 61 species in field quadrats. (The entire 15 ha field had 181 species of which only 67 were added after the first year. Four other species occurred only in seed bank samples). Of the 55 seed bank taxa, 15 made up 81 to 95% of the seed bank; of these, the most common were Aster pilosus, Conyza canadensis, Juncus spp., Lobelia inflata, Setaria faberi, and Veronica peregrina, which were 72% of the total. Densities of individual species varied significantly over the decade and with depth (0-3, 3-6, and 6-9 cm). Elimination of seed rain using exclosures maintained for one year caused a significant decrease in both seed bank density and species richness, Comparisons of seed bank species composition with the held vegetation showed divergence after the first year. Patterns of species importance (relative frequency) in the seed bank and in the vegetation varied over time. Importance of particular growth forms also varied with stage: in the seed bank the proportion of annual and perennial species remained similar, while in the vegetation, annual species declined as perennial and woody species increased, Exotic species were an important component of the seed bank (29.0 +/- 0.9%), vegetation (26.4 +/- 1.2%), and combined flora (37.7 +/- 3.1%). Seed bank dynamics and vegetation dynamics of early old field species were not similar, nor did seed bank patterns and life history strategies appear related.