B. Papp szerk.: Studia Botanica Hungarica 30-31. 1999-2000 (Budapest, 2000)

Papp, Beáta, Ódor, Péter; Erzberger, Peter: Preliminary data about the present Hungarian local populations of rare European bryophytes

graphical scale (SÖDERSTRÖM 1995). In an attempt to coordinate the conservation efforts of bryologists of different countries, the European Committee for Conservation of Bryophytes (ECCB) published the "Red data book of European bryophytes" (ECCB 1995). The bryophyte species rare in Europe are listed in it using standard IUCN categories (IUCN 1978) modified for bryophytes. After the publication of revised IUCN threat categories (IUCN 1994), these should also be applied to bryophytes (HALLINGBÄCK etal. 1998) when updating the information of the RDB. The Hungarian bryoflora was thoroughly investigated mainly by the tireless work of Ádám Boros and László Vajda. Their numerous bryofloristical publications were summarised in some handbooks (BOROS 1953, 1968, ORBÁN and VAJDA 1983). Their data concerning the localities of relatively rare bryophytes are also documented in their collections and their field diaries, which are kept in the Hungarian Natural History Museum (BOROS 1915-1971, VAJDA 1933-1978). However, these data mainly cover the period from 1930 to 1970. Today it is an important task to obtain information about the actual Hungarian distribution and population size of bryophyte species, which are rare or insufficiently known in Europe (which are, or potentially will be, included in the RDB). This floristical work is essential for the assessment of their conservation status, for finding their appropriate IUCN categorization, monitoring of their populations, conservation of species and their habitat and understanding of their ecological demands. Fifty bryophyte species occur in Hungary that are included in the RDB. Three of these are endangered (E), 12 are vulnerable (V) and the remaining species are rare (R) or insufficiently known (K) (Appendix). The aim of the authors' studies is to assess the actual rarity of these species by checking their earlier occurrences and by trying to find unknown local populations in their potential habitat. By the comparison of the present and earlier numbers of their occurrences and population sizes the change of their populations in Hungary could be estimated. Concerning these species similar studies are carried out in other European countries. This paper contains ( 1 ) some preliminary data of this floristical work, and (2) a case study about Fissidens arnoldii (a rare species in Europe), of which the actual Hungarian distribution and population size has been explored to a large extent, thus enabling the assessment of its threat category by IUCN criteria. METHODS To obtain the earlier distribution data of the investigated species the Bryophyte Herbarium of the Hungarian Natural History Museum, Budapest (BP)