Each collected sample was tagged, placed in a separate zip lock bag and preserved for transportation to Poland for future analysis. All samples were analyzed in the laboratory of the Institute of Archaeology and Ethnology Polish Academy of Science in Cracow. After measuring the volume 0.5–5 cm3, material was sorted under macroscopic binoculars. From each sample all plant material: seeds, caryopses, fruits and vegetative fragments like pieces of wood, leaves or stems, were selected. Plant material was found in 78 samples. Identification of seeds and fruits was based on a comparison with samples in a reference collection of the Institute of Archaeology and Ethnology PAS laboratory,

as well as the herbarium of the Department of CHIR-99021 concentration Paleobotany, OSI-027 W. Szafer Institute of Botany PAS and specialist literature (Klan 1947; Kowal 1953; Sajak 1958; Torin 2 Wojciechowska 1966, 1972;

Dörter 1968; Kowal and Rudnicka-Sternowa 1969; Swarbrick and Raymond, 1970a, 1970b; Rudnicka-Sternowa 1972; Conolly 1976; Rymkiewicz 1979; Cappers et al. 2006, 2009). Vegetative parts, including pieces of wood, were indentified according to their anatomic structures (e.g., Schweingruber 1990). Each fragment of wood was broken along three anatomical sections and examined microscopically, using a metallographic microscope. Identifications were made by comparison with anatomical atlases and specimens in a reference collection. Detailed information was obtained by studying one hundred slides with a scanning

electron microscope. Cumulative degree days for low-temperature Digestive enzyme vascular plant species (assuming that species can germinate, survive and grow above −5 °C; Bannister 2007) were calculated based on meteorological data for “Arctowski” oasis from our database. The risk index for “Arctowski” oasis were calculated according Chown et al. (2012a). Results During three seasons seventy-eight samples were collected. The distribution of plant material among the samples was irregular. In one sample there were many plant species recorded, whereas there were almost no plant remains in others. In general, plant material was very well preserved and contained intact diaspores, sometimes with traces of mechanic damage on the external surface. In total, 214 plant fragments were found (Table 1), among them there were 114 diaspores. In eleven samples (14 %) there were no diaspores. In average there were 1.7 diaspores per expeditioner (per person carrying seeds). There were 49 diaspores of species occur in cold region like Arctic and sub-Antarctic. Table 1 Type and number of plant remains preserved in 78 analyzed samples Type of specimens Numbers of specimens Wood 5 Spikelet 34 Leaves 26 Stem 5 Fruit scale 3 Seed 22 Fruit 71 Needle 26 Cone 1 Caryopsis 21 Total 214 The majority of plant material was assigned to forty-six species. Based on wood analysis only one tree species was identified as pine Pinus sylvestris (Table 2).