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

Papp, Beáta; Rajczy, Miklós: Contributions to the knowledge of bryophytes of the forests along the Fekete-Körös, SE Hungary

The important differences can be observed along the second axis (10.9% of the total variance); all of the ash and mixed forest stands have positive eigenvalues. The eigenvalues of all black locust and oak stands are in the negative range of the second axis. The third axis (8.3% of the total variance) "draws apart" the stands very well. On the plot a good correlation with the results of the cluster analysis can be observed, the members of the three groups obtained there can be encircled here. The biplot offers a good opportunity to find out which species are responsible for the separation of the groups. According to the biplot in the black locust stand some common bryophyte species (e.g. Brachythecium velutinum, Hypnum cupressiforme) can be found. The oak forests can be characterized mainly by Orthotrichum species, Tortula papulosa, Frullania dilatata occurring in the higher zone of trees and adapted to drier conditions and by pleurocarpous, mat forming, common species as Amblystegium serpens, Platygyrium repens. The corticolous bryophyte flora of the mixed forests is very diverse. Species adapted to higher humidity, with lax tufts or mat growing forms, as Porellaplatyphylla, Anomodon and Brachythecium species appear. Several species in these forests are rare in the Great Hungarian Plain, but frequent in montane forests; these are Isothecium alopecuroides, Homalia trichomanoides, Eurhynchium angustirete, Anomodon longifolius, Pseudoleskeella nervosa, Leucodon sciuroides. The latter bryophyte species are indicators of semi-natural, well-structured forests, where humid microclimate and good light conditions are provided for them. They are not common in the oak and black locust forests in the study area, as these stands are almost monocultures, with almost no "alien" tree intermixing. As one conclusion, the presence of a "closed forest" is not enough to support a rich bryoflora. Besides the role of the age of the forest stand, its structure, the level of mixing and the age distribution of the different tree species has a key importance. It was observed in the study area that for example if ash trees are among the mixing species, the otherwise closed canopy of other species is broken in a way that produces better light conditions for bryophytes. Consequently, we adorn the high importance of the establishment and maintenance of mixed forests; such forestry practices are desirable and beneficial for nature conservation. Acknowledgements - Many thanks for the help on the field and the financial support to the Körös-Maros National Park.