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Dendrochronological dating of geomorphic processes in the High Arctic

Owczarek P.

Landform Analysis

2010

Vol. 14

45-56

Dendrochronological methods were used to analyze geomorphic processes in the Arctic area. Samples of dwarf shrubs, Salix polaris and Salix reticulata, were collected from different morphodynamic surfaces: talus cones, debris flow tracks and fluvioglacial terraces. Clearly visible, countable and measurable annual growth rings (ranged from relatively wide 0.8 mm in width, to extremely narrow rings less than 0.01 mm in width) and wood anatomical changes (scars, tension wood) allow for using these species in dendrogeomorphological examinations. The age of the dwarf shrubs showed the minimum time during which the surface was disturbed by mass movements (e.g debris flow tracks developed in the early 1950s and 1970s) or the time of plant colonization which indicates disappearance of geomorphic processes (e.g. determining the age of fluvioglacial terraces in the Arie valley). Dwarf shrubs represent problems in synchronization of growth curves (discontinuous rings, missing rings, asymmetric geometry of stem). Samples taking from random surfaces can reflect only local phenomenon, which are limited to microtopography. It is necessary to -analyze material from entire area of geomorphic form.

Impact of ultraviolet-B radiation on two species of forest dwarf shrubs : bilberry (Vaccinium myrtillus L.) and cowberry (Vaccinium vitis-idaea L.)

Robakowski P.

Polish Journal of Ecology

1999

Vol. 47, no 1

3-13

Impact of UV-B irradiation on chlorophyll content and chlorophyll fluorescence of two dwarf shrub species: Vaccinium myrtillus L. and Vaccinium vitis-idaea L. was investigated. The plants originating from different latitudes were used. The experiment was carried in the greenhouse. Three variants of ultraviolet-B irradiation were applied = O, lower dose = 11.32 and higher dose = 22.64 kJ m^-2 day^-1 UV-B[BE] (biologically effective dose of UV-B). Measurements of chlorophyll fluorescence and chlorophyll content were carried out. The response of dwarf shrubs to the increased UV-B radiation depended on UV-B dose, species traits and provenance. Vaccinium vitis-idaea was less sensitive to UV-B than Vaccinium myrtillus. The permanent discoloration was observed only on Vaccinium myrtillus leaves. The leaf bud brea of this species was accelerated at high UV-B dose compared to the control. The UV-B radiation influenced its photosynthetic apparatus: the chlorophyll content in leaves was reduced, the maximal and the steady state fluorescence of chlorophyll were diminished. The chlorophyll content in leaves of Vaccinium vitis-idaea did not change significantly but the relative vitality index and the steady state fluorescence were modified under the influence of the radiation.