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Vegetation data (70 relevés) of ephemeral wetlands collected in both permanent and temporal water basins were analyzed. Numerical classification of the data revealed two distinct subsets, the first comprised communities of Eleocharition ovatae Philippi 1968 alliance, the second combined communities dominated by Alisma lanceolatum, Isolepis supina or Elatine alsinastrum (Alisma lanceolatum group). Phytocoenoses of Eleocharition ovatae were widely distributed in the study area and developed, most frequently, on exposed bottoms of fishponds. This group could be divided into four types of communities. Patches representing Alisma lanceolatum group were found only in mid-field depressions periodically filled with water and concentrated in Volhynian Upland. In this group, two lower vegetation units were distinguished.

Spatial distribution and habitat preferences of 55 river corridor plant species were analyzed on a local scale in the valley of a medium-size regulated river. The analysis was based on the results of a detailed mapping on a 50 km-long section of the Lower San River valley (366 cartogram cells of 1 square km). Selected species were divided into two groups: (1) strictly and (2) loosely confined to river corridors. River corridor plants were found throughout the valley (river channel, active and historical floodplain, older terraces, slopes); however, their frequency was diverse in particular areas. The highest concentrations were observed on the floodplain. Their number decreased towards the border areas of the valley. Species which were less confined to rivers were found more frequently in the valley (one species occupied, on average, 12.9% of grid cells), than plants strictly confined to the river system (one species occupied, on average, 5.9% of grid cells); however, the ranges of species of the second group were more restricted to the Holocene part of the valley, especially to the floodplain. River corridor plants were, ecologically, a highly diversified group. In the San river valley, they were found in riparian forests, pioneer ephemeral communities on the banks of water bodies, dry grasslands, meadows and old river beds; a lot of them grew in ruderal habitats.

The paper presents the results of the research on Usnea florida in the Polish Eastern Carpathians. Three new sites of this species have been found in the Bieszczady National Park at an altitude of 800-880 m. U. florida grows on the bark of Fagus sylvatica, Populus tremula and Betula sp. The historical sites of this species in the Western Bieszczady Mts. have not been confirmed. In Poland U. florida has also been recorded in the Białowieża Forest and Gdańskie Pomerania.

The aim of the present study was to describe the distribution of xerothermic species of vascular plants in the lower San River valley and the relationship between their density and the intensity of selected environmental (natural and anthropogenic) factors. Xerothermic species occurred more frequently in the present valley floor compared to the glacial terrace. Within the present valley, the highest density was observed in the floodplain. The examined species also occurred more often on steep slopes of the valley, at the margins of the present valley terraces, and in the area of occurrence of aeolian sands. Moreover, a positive correlation has been found between the number of xerothermic species and the area of polyhemeroby ecosystems. The distribution of xero- and thermophilous species is determined by natural edaphic and geomorphological factors as well as anthropogenic ones (land use, lowering of the groundwater level as a result of river regulation).

The environmental variability during the Mazovian/Holsteinian interglacial is better understood thanks to the results of multidisciplinary palaeobotanical studies. The perfectly preserved and abundant material from Nowiny Żukowskie in SE Poland has been the subject of numerous palaeobotanical analyses. The results both of initial pollen analysis and of the examination of plant macroremains provide a detailed view of changes in the palaeoenvironment of this area during the Mazovian/Holsteinian interglacial. Originally, the water basin was mostly the habitat of plants indicative of low trophy. The frequent occurence of swamp plants evidences a change in hydrological and climatic conditions consistent with the intra-interglacial climatic oscillation. In the subsequent part of the optimum, an expansion of swamps with Aracites interglacialis and Dulichium arundinaceum was recorded. The development of a peat bog overgrown by i.a. Sphagnum sp., Eriophorum vaginatum, and Andromeda polifolia was also observed. The growth of swamp and peat vegetation resulted in the nearly complete disappearance of aquatic vegetation, apart from species typical of the climatic optimum of the Mazovian/Holsteinian interglacial: Brasenia borysthenica and Aldrovanda dokturovskyi. The close of the interglacial was marked by the intensive development of peat bog and swamp communities with Carex rostrata, Menyanthes trifoliata, and A. interglacialis. The intensive increase in the number of A. interglacialis during the period described as the “birch oscillation” supports the hypothesis of noticeable changes in hydrological conditions at that time. The end of the described period is typified by a deterioration of climatic conditions, indicated by the increase in values for Betula humilis, B. nana, and Juniperus communis.