Primary succession on a beach plain: species dynamics in relation to bioimass and nutrient accumulation

The present study reports on a primary succession series which started on the bare beach of the Dutch island Schiermonnikoog after the building of a sand dike in 1959. Vegetational changes were studied by means of permanent transects. Soil development and vegetation structure during this successional series could be reconstructed, since several stages of this succession were present in the same part of the island. Salinity, moisture content and flooding are considered to be major determinants of the spatial variation, ranging from saline, wet plains to dry, fresh dunes, and are likely to be responsible for the year to year fluctuations of short-living species. However, these factors did not show a trend in time. From soil analyses it is argued that nitrogen limits the total biomass. In about 16 years the total amount of nitrogen in the organic layer of the soil increased from 7 to 50 g N m in the plains and from 1 to 15 g N nf2 on the dunes. The accumulation of nitrogen during succession is accompanied by an increased biomass, a decreased light penetration to the soil-surface, a decreased proportion root, an increased proportion stem, an increased plant height at maturity, and a decreasing abundance of short-living species. Only during the first stage on the dry dunes sand-blowing is considered to prevent small species from establishing. With the exception of this early dune stage, our observations are in agreement with the resource ratio hypothesis of Tilman (1985). Causes of the high rates of nitrogen accumulation in the soil are discussed. The observed nitrogen accumulation, which is considered to be an important determinant of the successional dynamics, is thought to be facilitated by the vegetation.