Constraints on the assembly of cliff communities at the seed bank stage

Seed banks on cliffs of the Niagara Escarpment, southern Ontario, Canada, w ere examined and compared to different, but immediately adjacent, communiti es on plateaus and talus slopes to evaluate the role of the seed bank in co ntrolling the mature vegetation of cliff-face communities. Soil samples wer e collected five times at two sites over three years. Data were analyzed th ree ways: multiple discriminant analysis on community composition, univaria te ANOVAs of seed density data, and analysis of seed characteristics. The e mergence of constraints on final plant community structure was dearest for the discriminant analysis: year of collection separated the seed bank centr oids the mast, but a secondary effect we observed was the clear separation of the three community types and their association with species found in th eir specific mature communities. ANOVAs and the analyses of seed characteri stics did not show statistically significant community-related sorting. Alt hough the cliff-face community structure was discriminated at the seed bank stage, it was not directly correlated with the above-ground vegetation; th erefore subsequent processes such as seed germination and seedling survivor ship must also be responsible for final community composition.