Factors affecting primary succession of glacier foreland vegetation in the European Alps

Vegetation succession on glacier forelands has been well-studied. However, most of the studies investigated only one or few glacier forelands. We studied regional variations in vegetation succession on 16 glacier forelands in the European Alps. To improve our understanding of how vegetation succession is regulated by environmental conditions, we took edaphic and climatic factors into account. We collected vegetation data in three stages (early; middle; late) along a successional gradient on glacier forelands in the Eastern and Western European Alps. The progressions of species richness, vegetation cover and composition during primary succession were compared between these two regions. In addition, the effects of climatic and edaphic factors and grazing were tested. Our results reveal that the vegetation from the early stage did not differ between the regions and different elevations. With progressing time, and especially in the late successional stage, several vegetation differences emerged. The forelands of the Western Alps already developed to open shrubland, while the forelands of the Eastern Alps so far only developed toward grassland. Surprisingly, these differences cannot be explained by different precipitation amounts, but possibly by different regional species pools and elevations of the treelines. We conclude that a complex of edaphic factors closely related to terrain age, regional differences in the species pool, and the different elevation of the treeline in the eastern and western Alps mostly influenced later stages of primary succession on glacier forelands.