Carbon and nitrogen in soil and vegetation at sites differing in successional age

We studied vegetation and soil development during primary succession in an inland drift sand area in the Netherlands. We compared five sites at which primary succession had started at different moments in the past, respectively 0, 10, 43 and 121 years ago, and a site at which succession had not yet started. In the three younger sites the vegetation was herbaceous, whereas in the two older sites a pine forest had formed. Forest formation was accompanied by the development of an FH-layer in the soil, an increase in the amount of soil organic matter, and an increase in nitrogen mineralisation rate from 1.9 to 18 g N m(-2) yr(-1). Soil moisture content also increased, whereas pH showed a steady decrease with site age. The vegetation changed from a herbaceous vegetation dominated by mosses and lichens and the grass species Corynephorus canescens and Festuca ovina towards a pine forest with an understorey vegetation dominated by Deschampsia flexuosa and, at the oldest site, with dwarf shrubs Empetrum nigrum and Vaccinium myrtillus. At the same time the total amounts of carbon and nitrogen of the ecosystem increased, with a relatively stronger increase of the carbon pool. The establishment of trees during succession greatly affects the dynamics of the ecosystem, especially its carbon dynamics.