Geographical Differentiation of the Floristic Composition and Structure of the Herb Layer of Forest Permanent Plots in East Germany , Poland , and Belarus

The influences of a geographical location on floristic composition, horizontal structure, and biomass of the herb layer in pine and mixed pine forest communities along climatic and pollution gradients in East Germany, Poland, and Belarus were determined. Phytosociological records were collected in permanent plots in May 1995. Each record covered an area of 400 m2. The floristic composition of the study area provided the basis for the determination of the phytosociological differentiation of the plots along the transect. Similarity index between plots was calculated by using the Czekanowski index; a similarity dendrogram was constructed according to Ward’s method. Biomass was determined in six 0.1 m2 replications sampled in each permanent plot. All of the identified study areas were representative of the Dicrano-Pinion alliance and included two communities of pine forest (Peucedano-Pinetum and LeucobryoPinetum) as well as the community of mixed pine forest (Querco roboris-Pinetum). On the basis of similarity indices, two geographical groups of plots were distinguished: suboceanic and subcontinental. Geographical differentiation of the stands is related to the presence of the groups of species of different geographical distribution type. For the western part of the transect, characteristic species are Deschampsia flexuosa and Leucobryum glaucum. Central and eastern parts are characterized by the presence of the following species: Melampyrum pratense, Luzula pilosa, Veronica officinalis, Lycopodium clavatum, Peucedanum oreoselinum and Scorzonera humilis. On the stands located on the easternmost part of the transect (Belarus) frequent species are: Pirola chlorantha, Chimaphila umbellata, Koeleria pyramidata and Hypochoeris maculata. The ground flora of the identified areas was not uniform; rather it was characterized by a mosaic of sparse populations of plants. In general, three types of these systems can be distinguished: one is dominated by a cover of mosses, the second is dominated by dwarfshrubs, and the third by species of grass. The ground cover biomass on the west-east transect ranged from 49 to 544 g/sq. m, but for pine forests the correlation between geographical longitude of the stand and biomass of mosses (corr. coeff. 0.701) and total biomass of the ground cover (corr. coeff. 0.779) was statistically significant. Introduction This article presents a geobotanical analysis of the floristic composition of the herb layer and its structure and biomass in East Germany, Poland, and Belarus. It constitutes part of long-term, in-depth community research aimed at defining the influence of geographical location on pine forest ecosystems, in particular pine forests and mixed/pine forests (Breymeyer 1996, Degórski 1996, Smialkowski 1996). The subjects of geobotanical analyses consisted of 17 permanent plots lying along a west-east transect following the gradient of continentality. These are mature or almost mature pine stands, basically single-species and single-aged (60-95 years). All the analyzed forest communities represent (in accordance with phytosociological typology) the Dicrano-Pinion alliance, and within it two communities of pine forest, Peucedano-Pinetum and Leucobryo-Pinetum, as well as the community of mixed pine forest, Querco roboris-Pinetum. In accordance with the principles of forest typology these are different forms of pine forest occurring on sandy substrates. Their economic use does not differ significantly. The level of differentiation of the herb layer is one of the more important structural characteristics of forest phytocoenoses. On the one hand it influences the spatial differentiation for various processes like the production and decomposition of organic matter, and on the other it may be an indicator of habitat microdifferentiation (in particular topography, fertility, and humidity). A way of describing the level of diversity of the herb layer is through the identification, Geographical Differentiation of the Floristic Composition and Structure of the Herb Layer of Forest Permanent Plots in East Germany, Poland, and Belarus1 1 An abbreviated version of this paper was presented at the International Symposium on Air Pollution and Climate Change Effects on Forest Ecosystems, February 5-9, 1996, Riverside, California. 2 Botanists, Institute of Geography and Spatial Organization, Polish Academy of Sciences, 00-927 Warsaw, Krakowskie Przedmiescie 30, Poland.