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KOJIMA, SATORU  Tokyo Woman's Christian University.

Vegetation development in recently deglaciated terrains in Ny-Alesund, Svalbard, was studied. Vegetation types were identified based on floristic structure of the plant communities. They were correlated with soil characteristics and key factors regulating vegetation differentiation were determined.

Ny-Alesund is located in the northwestern corner of Spitzbergen Island, Svalbard. Its latitude is approximately 78˚55’N and longitude 11˚52’E. Climate of the area is typically frigid and humid with mean annual temperature of –5.2C, mean monthly temperature of the warmest month 5.4C, and that of the coldest month –15.5C. Annual total precipitation is approximately 400 mm. Such a climate may be classified as ET type (tundra climate) of Köppen’s classification. Geology of the area is dominated by Carboniferous and Permian sedimentary rocks predominantly of calcareous and dolomitic nature. Entire area was once covered by glaciers. There are some extant glaciers that have been receding quite rapidly in a rate of approximately 10 m/year on a low and gentle topography. Geomorphology of the area consists basically of a confluent glacial outwash plain of extant glaciers West Brogger and South Brogger Glaciers. In the forefront of those glaciers, there is a vast extent of recently deglaciated exposed terrains, where vegetation succession progresses. Therefore, most of the vegetation is in the early to intermediate stages with some in the stable stage of succession.

Throughout the study area, a total of sixty relevés of 2 m x 2 m size were established to represent various kinds of vegetation. For each relevés, all the vascular species were listed and their coverage was assessed. From each relevé, one soil sample representing top 10 cm of the solum was collected. The samples were later analyzed for physical and chemical properties.

Based on the floristic characteristics, seven vegetation types were distinguished. They were: 1. Draba nivalis type, 2. Dryas integrifolia type, 3. Cerastium arcticum type, 4. Cassiope tetragona type, 5. mesic moss type, 6. Saxifraga caespitosa type, and 7. Luzula arctica type.

The Draba type develops in habitats of soils excessively well drained and over-saturated with basic cations but poor in organic matter; the Dryas type occurs where soils well-drained and high with basic cations with high soil pH; the Cerastium type in mesic habitats of soils rich in basic cations and high in electric conductivity; the Cassiope type in mesic habitats with low soil pH and base saturation; the mesic moss type in habitats moderately drained and low in base saturation and poor in calcium and magnesium; the Saxifraga type in habitats poorly drained and intermediate in amount of basic cations; and the Luzula type in water-saturated habitats and low in basic cations.

In terms of vegetation succession, the Draba type and the Luzula type both indicate early stage of succession, and the former represents extremely dry habitats while the latter very wet habitats. The Cassiope type and mesic moss type both represent more or less stable stage of the succession. The former indicates somewhat base-impoverished soil while the latter relatively base-rich soil conditions. Other types represent more or less intermediate stage of the succession. It was thought that vegetation of the area would eventually converge to and be represented by the Cassiope type or moss type, depending on chemical characters of soils, as the succession well advanced.

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