Seed distribution drivers at an early stage of vegetation development in a sand quarry

Distribution of viable seeds on the bare ground slope in a sand quarry located in the vicinity of Saint-Petersburg was studied in relation to the relief of the ground surface, species composition of pioneer communities and surrounding vegetation, as well as the timing of a growing season. Seeds were found even on bare ground and poorly vegetated sites. Ground contains three times more seeds in autumn than in early summer. Most of seeds belonged to perennial grasses (mainly anemochorous, apophytes, and weeds), with a few coming from other life-forms (from annuals to trees), which were spread in the quarry or in the surrounding vegetation. Seeds concentrated on the slope, their number was the lowest in the quarry bottom in both observation periods, since conditions favored to plant germination there. The microrelief of the ground surface can also influence seed distribution: in June, viable seeds mostly located in depressions. We suppose that in dissemination period, seeds of anemochorous plants concentrate on hillocks which trap them; however, more data is needed to conclusively prove this hypothesis