COLONIZATION DYNAMICS IN A MOSAIC LANDSCAPE - THE BURIED SEED POOL

In a landscape mosaic of old fields, young successional forest, conifer plantations, floodplain forest, and upland mixed deciduous forest, buried seed pools were compared with the established vegetation and dispersal seed pool. On a finer scale, I examined the importance of within-community microsites (treefall mounds and pits) to the maintenance of invading species in mature deciduous forests. Hypotheses addressed whether the buried seed orignated as persistent remnants from past successional stages, or was supported by active seed dispersal within and between communities. Generally the buried seed pool had a higher similarity to the vegetation of a site than found in other studies. Percentage of buried seed appearing in the vegetation was highest for young forest, followed by floodplain forest, conifer plantation, old fields, and upland forest microsites. Per cent similarity of species in the buried seed pool was lowest between old fields and adjacent communities, not supporting the idea that buried seed largely reflects past successional stages. Similarity of species between sites was low for the vegetation, but high for the dispersal pool. Patterns of buried seed corresponded closely with those of dispersal rather than stand age. Those species with wide distribution in the seed pools across communities were usually most abundant in vegetation of one site, but not necessarily in younger sites. Species with statistically significant distributions of buried seed mostly occurred in greatest abundance in the vegetation of a different site than where buried seed was most abundant. Common field buried seed species were most abundant in forest vegetation, for example. Upland forest microsites had low correspondence between buried seed pool and vegetation. Mound and pit buried and dispersed seed pools were very similar, although vegetation was not. The few species most characteristic of mound or pit vegetation were represented in the buried seed pool. Most of the species in the upland forest buried seed pool came from neighbouring communities of all ages, and were found in active dispersal pools. These invading species did not establish selectively in upland microsites, being found in both mounds and pits. Thus mound and pit microsites do not contribute to the colonization of invading species, nor do they contain a discriminating record of past species composition as buried seed. However, inter-community colonization through active seed dispersal does add to the richness of the communities in this landscape mosaic.