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Dendrochronology and extreme pointer years in the tree-ring record (AD 1951–2011) of polar willow from southwestern Spitsbergen (Svalbard, Norway)

Owczarek P., Opała M.

Geochronometria

2016

Vol. 43, no. 1

84--95

Greater warmth and precipitation over the past several decades in the High Arctic, as recorded in meteorological data, have caused shrub expansion and affected growth ring widths. The main aim of the study was to develop a tree-ring chronology of polar willow (Salix polaris Wahlenb.) from southwest Spitsbergen, attempt to explain its extreme pointer years (extremely low value of growth-ring widths) and to demonstrate the dendrochronological potential of this species. This plant is a deciduous, prostrate, creeping dwarf shrub that produces anatomically distinct annual growth rings with the consistent ring width variation. After using serial sectioning we developed rigorously cross-dated ring width chronology covering the period 1951–2011. Since the beginning of the 1980s an increase of the mean and maximum growth ring width has been observed which is consistent with the increase of both temperature and precipitation in the Arctic reported from meteorological sources. Nine negative extreme years were distinguished and explained by complex hydroclimatic drivers, which highlight the importance of availability of moisture from snowpack and spring precipitation. An additional negative factor present in the years with very low dwarf shrubs growth is rapid thawing and fast freezing during winter as well as low sunshine duration. Our results contradict the prior assumption that inter-annual tree growth variability of dwarf shrubs from polar regions is controlled simply by temperature.

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.