Species pool: the concept, its determination and significance for community restoration.

. The concept of species pool is reviewed. It is suggested to maintain the terms regional pool and local pool but replace actual pool by community pool. The regional and local pool are considered as selections from the regional and local flora based on ecological similarity. It is also suggested to include in the community pool a selection of species present only as diaspores in the diaspore bank (including diaspores from the seed rain), the selection being based on the same ecological criteria. Four approaches to determine the species pool are discussed: ecological, functional and phytosociological similarity, and an experimental approach. The phytosociological approach appears to be promising. The species pool is elaborated as a fuzzy set in the sense that each species of a community or a local or regional flora is a member of any community, local or regional species pool with different degrees of membership. This membership is defined as a probability of a species to become part of the community pool of a target community which is a function of the ecological (environmen-tal/functional/phytosociological) similarity of the species with the target community; the shortness of the distance of its nearest populations, the frequency/abundance, the dispersal capacity, the actual presence of dispersal mechanisms, the germinability of newly arrived diaspores, and the longevity of seeds (viability) in the diaspore bank. The information on species pools is needed for designing experiments where the number of species in a community is to be manipulated, for instance in restoration management.