Editorial

The majority of papers in the present special feature of Acta Botanica Neerlandica deal with dispersal of diaspores and related discussions about re-introduction of endangered plant species. After having considered the criteria for the introduction of species, papers follow on seed bank characteristics at the plant community level, changes in dispersal processes with respect to changing land use, and dispersal characteristics. With a few exceptions, the majority of plant communities harbouring endangered plant species tend to contain a short-term persistent seed bank. This implies that restoration management cannot rely on the seed bank. There would, then, be no problem if dispersal was as accurate as assumed on the basis of the dispersal structures of seeds and fruits. However, even pappus-bearing fruits, such as those of Arnica montana, show poor wind dispersal. Moreover, those fruits that travel longest distances appear to be non-viable. Also, diaspore dispersal by machinery and livestock is much lower than it was in former centuries, in low-intensity farming systems. So far we have considered the state-of-the-art about conditions for spontaneous reestablishment in western European grasslands, from the plant characteristic point of view. The next and indispensable step is to ascertain that the abiotic conditions (hydrology and nutrient availability) and biotic conditions (interactions with established vegetation) of the target site of re-introduction will turn out to harbour safe sites. This aspect, meanwhile, can be experimentally tested by artificial introductions.