The higher availability of N and P in lime-poor than in lime-rich coastal dunes in the Netherlands

1 Measurements of above-ground productivity, plant nutrient levels, in situ mineralization and litter decomposition in four localities differing in soil chemical conditions were used to assess the availability of N and P in Dutch coastal dune grasslands. 2 P-availability is regulated by soil chemical conditions and seems to be a key factor regulating biomass production, whereas N-availability seems to be determined by litter input from this biomass, and thus indirectly controlled by P. 3 Contrary to expectation, N-availability is much higher in acid soils (with low rates of decomposition and high soil C : N ratios) than in calcareous soils (with high decomposition and low C : N ratios). Similar results have been reported from other ecosystems and may be due to a lower microbial N-demand at low rates of decomposition, increasing the amount of N left over for the vegetation. 4 In contrast to 'conventional wisdom', low-degradable litter maybe a good plant strategy to improve the ecosystem recycling of nutrients and increase their availability. This may at least partly explain the success of Ammophila arenaria in lime- and iron-poor dunes.