Seed bank formation during early secondary succession in a temperate deciduous forest

Authors


and present address: Laura Hyatt, State University of New York, Department of Ecology and Evolution, Stony Brook, NY 11794–5245, USA (tel. 516 632–1381; fax 516 632–7526; e-mail lhyatt@life.bio.sunysb.edu).

Summary

1 Seed banks are dynamic entities, with input occurring through dispersal and loss occurring through germination and various sources of mortality. Measures of abundance of seeds in the soil at one point in time cannot distinguish those seeds destined to germinate or die in the next growing season from those entering the long-term seed bank, and cannot therefore reveal the proportion of seeds that are carried over from year to year.

2 We studied seed bank dynamics in a 2.5-ha deciduous forest gap by following the fate of a single year’s cohort of seeds over 2 years. Seed input for 1 year, subsequent in situ germination and survivorship were measured at 60 locations. We examined how temporal changes in seed bank composition were affected by the presence of the dominant gap colonizing species Rubus allegheniensis.

3 Over the course of 2 years, both mean seed density and its variance declined. The temporal changes in density were not, however, accompanied by detectable changes in diversity.

4 Three species (R. allegheniensis, Phytolacca americana and Paulownia tomentosa) dominated the seed bank. Seed bank accumulation patterns in Rubus and Phytolacca showed contrasting responses to the presence of Rubus, with Phytolacca excluded from seed banks in such patches through reduced input and increased mortality.

5 First year germination and post-dispersal mortality interact with seed input to influence the spatial distribution of density and diversity in the long-term seed bank. Substantial long-term seed banks do form within temperate forest gaps and patterns of above-ground vegetation can have substantial effects on their dynamics.

Ancillary