Heathland plant species composition and vegetation structures reflect soil-related paths of development and site history

Questions To improve our knowledge on how environmental conditions determine the development of high-value Calluna vulgaris heathland habitats, we studied the floristic and structural characteristics of heathland plant communities across North Germany and how they are influenced by edaphic, climatic and management factors. We ask how heathland development is related to these factors and what are the implications for conservation management and restoration. Location North German Plain. Methods We collected 350 releves in 18 dry Calluna heathland areas. Plant communities were classified using Isopam, and Redundancy Analysis (RDA) determined effects of environmental conditions. Potential pathways of development and the nature conservation status of the communities were identified on a multifactorial basis. Results We found nine floristically and structurally distinct heathland plant communities. Heathland vegetation showed distinct patterns along Calluna age development stages and environmental conditions. Soil conditions and related effects of long-term site history and recent management turned out to be the predominant factors influencing species composition and diversity, resulting in three potential heathland succession pathways. Mosaic-like communities with particularly high taxonomic diversity and conservation value occurred on early-successional inland dunes or as regeneration stage growing on nutrient-poor sandy soils without humus accumulation. Conclusions The study reveals fundamental differences between historically farmed heathland in the oceanic Northwest and former military training areas mainly in northeastern Germany with consequences for restoration ecology. Present nature conservation criteria turned out to be insufficient in predicting habitat quality, as lichens are frequently disregarded. Our findings highlight the need for intense soil disturbance to maintain early-stage soil conditions and a diverse Calluna growth-phase composition, as these factors essentially determine species richness in lowland heaths.