critical load of nitrogen


Assessment of the critical load of nitrogen in coastal haeathlands dominated by Calluna vulgaris

Project duration

2012 - 2015

Brief description of the project

Heathland ecosystems, which were very common in Northern Germany in former times, are nutrient poor environments especially with a lack of nitrogen. Typical plants of dry lowland heaths such as Calluna vulgaris are well adapted to these conditions. Increased emissions from agriculture and fossil fuel burning in industry and traffic resulted in increased airborne concentrations of reactive nitrogen compounds (mainly NHx, NOy) during the last decades. The traditional land use with grazing, sod cutting and controlled burning has mostly surrendered, which led onto an accumulation of nutrients. As a result of this, the state of competition in nitrogen sensitive ecosystems has shifted to an advance for fast growing nitrophilous species. For heathlands this usually means that this leads to a transition into grassland and as a consequence, a loss of biodiversity.

To protect heathlands against further degradation in a sustainable way it is important to know how much nitrogen a heathland can tolerate without a visible interference of its functionality. This critical load for the nitrogen deposition will be determined by an experimental fertilisation with graduated nitrogen concentration.

Our experimental area is situated in lichen rich Calluna heathland on sand dunes of the island of Fehmarn (Schleswig-Holstein, Germany). This area is particularly suitable for this experiment because of its natural low nitrogen deposition.


Federal Environmental Agency

Participating individuals from the institute

Prof. Dr. Werner Härdtle (Project director)

Alexandra Bähring (Spokersperson)