Effects of nitrogen deposition on soil and vegetation in primary succession stages in inland drift sands

Background and aims
Primary succession was studied in acid inland drift sands. Main research questions were: 1) How do vegetation and soil change during succession? 2) How are soil parameters and species abundance affected by atmospheric nitrogen deposition?
Methods
One hundred sixty-five plots were selected in 21 drift sands throughout The Netherlands, divided over eight succession stages from bare sand to dry heath and within a gradient in nitrogen deposition. Vegetation development and soil parameters were described and water-extractable elements measured and differences between high (>30 kg N ha−1 year−1) and lower nitrogen deposition sites calculated.
Results
Vegetation cover and height increased during succession. Lichens contributed most to plant species diversity. Thickness of Ah horizon increased and pH decreased and concentrations of Fe, Al, S increased. Base cations increased as well, despite the drop in pH. Also, water-extractable ammonium, nitrate and phosphate increased, along with the NH4:NO3 ratio. Sites with high nitrogen deposition had higher NH4:NO3 and Al:Ca ratios, lower pH, higher cover of algae, lower lichen and total species diversity, more Pinus sylvestris seedlings and more species of late succession stages.
Conclusions
Drift sand succession seems to be mainly driven by an increase in organic matter, but is accelerated by nitrogen deposition.