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

Abstract

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 growthring 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.

Origin, activity and environmental acclimation of stem secondary tissues of the polar willow (Salix polaris) in high-Arctic Spitsbergen

“…Betula nana, Cassiope tetragona, Rhododendron lapponicum and Empetrum nigrum (Blok et al 2011(Blok et al , 2015Schweingruber et al 2013;Büntgen et al 2015;Li et al 2016;Iturrate-Garcia et al 2017;Weijers et al 2017). In addition, the representatives of the Salix genus such as S. arctica (Woodcock and Bradley 1994;Schmidt et al 2010;Schweingruber et al 2013), S. lanata (Forbes et al 2010), S. reticulata (Owczarek 2010), S. pulchra (Blok et al 2011;Iturrate-Garcia et al 2017) and S. polaris (Owczarek 2010;Buchwal 2014;Owczarek and Opała 2016;Opała-Owczarek et al 2018;Sandal 2017;Le Moullec et al 2018) are commonly analysed with the use of dendrochronological methods. Among them, the polar willow (Salix polaris) is of particular importance, as a pioneer species playing a crucial role in colonisation of e.g.…”

Two centuries-long dendroclimatic reconstruction based on Low Arctic Betula pubescens from Tromsø Region, Northern Norway

“…Recently, many dendroecological and dendroclimatological studies based on growth-ring variability of tree, shrub and dwarf shrub species have been carried out in polar and subpolar regions (e.g. Woodcock and Bradley 1994;Rayback and Henry 2006;Bär et al 2007;Weijers et al 2010;Blok et al 2011;Buchwal et al 2013;Owczarek and Opała 2016). The growth rate, ring width variability and changes in wood anatomy of polar plants can also be a source of valuable information about the activity of geomorphic processes (e.g.…”

Annual ring growth of a widespread high arctic shrub reflects past fluctuations in community‐level plant biomass

“…This is in line with previous findings across arctic and alpine shrubs (Ackerman et al, ; Buchwal et al, ; Elmendorf et al, ; Forbes et al, ; Myers‐Smith, Elmendorf, et al, ; Van der Wal & Stien, ; Weijers et al, ). Sun exposure has also been suggested to potentially influence S. polaris ring growth on Svalbard (Owczarek & Opała, ), and that of the net above‐ground production of tundra vascular plants in general (Muraoka et al, ; Van der Wal & Hessen, ; Wiegolaski, Bliss, Svoboda, & Doyle, ). Van der Wal and Stien () pointed at the importance of cloud cover rather than just summer temperature in our study area, and suggested that temperature could be a good index of photon flux density necessary for carbohydrate production in the photosynthetic process (Muraoka et al, ).…”

“…Its abundance and high digestibility make it an important food resource for herbivores, especially reindeer (Bjørkvoll, Pedersen, Hytteborn, Jónsdóttir, & Langvatn, 2009;Van der Wal et al, 2000). The species has been reported to live for many decades, with a mean plant age of around 40 years (Buchwal et al, 2013;Owczarek & Opała, 2016). The oldest known individual was 120 years old (A.…”