Primaire successie op de kwelder in relatie tot stikstof in de bodem

Primairy Succession on coastal barrier islands was investigated using Chronosequences. During 200 years on Schiermonnikoog (The Netherlands), 65 years on Terschelling (The Netherlands) and 100 years on Skallingen (Denmark) vegetation changes were related to the N pool size in the top soil. The work which was done by 01ff (1992), was used in order to generalise the succession found on Schiermonnikoog for other coastal barrier islands. More than 7000 recordings of the plantspecies were taken. Only 144 soil samples for the N pool size •were possible, due to time constraints. Therefore, the N poo1 size was related to the thickness of the clay layer, which could be measured much faster. This gives a linear relationship. The N pool size increases with increasing clay thickness. In order to explain variation in clay thickness, a response surface of the clay thickness dependent on the age of the marsh and the watercolumn was made. The total watercolumn above the ground (since the development of the salt marsh) was calculated by multiplying the watercolumn with the age of the salt marsh. It appeared, that the clay thickness showed a linear relationship with the total watercolumn. On Terschelling the clay accumulation was more than twice as fast as on Schiermonnikoog and Skallingen. This could not be explained. Response surfaces of the different plant species were made, dependent on age and watercolumn. The use of dominance and the use of presence of plantspecies was compared. There appeared to be no real difference between the two methods. With the use of presence, more species could be used, but with this method, it was less clear whether the abundance of species increased or decreased. Therefore the probability of dominance is also useful to describe succession. Finally, it was difficult to generalise the response surfaces of schiermonnikoog for other coastal barrier islands. It became clear that the species distribution on Skallingen and Terschelling was comparable with the species distribution on Schiermonnikoog, but to generalise the succession on Schiermonnikoog, more data are necessary.