Salix polaris radial growth responses to 11-years of warming experiment in Adventdalen (central Spitsbergen)

Dwarf shrubs are the northernmost woody plants living under extremely harsh conditions and thus their growth is expected to be extremely sensitive and responsive to even slight changes in climate. The study of how shrubs annual growth respond to changes in the climatic conditions can supply relevant data on how Arctic vegetation will develop under future warming scenario. Although many studies described phonological responses of Arctic shrub growth to experimental warming, little is known about radial growth performance of woody plants within the commonly used across the Arctic open top chambers (OTCs) warming treatment. The recent results from experimentally elevated temperatures studies indicated that tundra vegetation exhibits strong regional variations in response to warming. This highlights that a mechanistic response to both current and modelled climate warming needs to be better understood both at the species anatomical level and in the longer time-scales. More than 10 years of warming treatment in Adventdalen (Spitsbergen) give an excellent opportunity to study plant radial growth response to warming encoded in annual shrub-rings pattern. The woody plant material will be collected from experimental plots (open top chambers, OTCs) and compared with unmanipulated plant growth from the control plots. A 13-years warming treatment will be assessed both at the radial growth and wood anatomical level, mainly through annual vessel size characteristics. The application of serial sectioning and both dendrochronological and quantitative wood anatomy measurements will enable to better assess the plant growth adjustment to warming conditions. The results of the proposed WarmDendro project will be further compared with the on-going study conducted by the Project Owner in Northern Alaska (Toolik Lake Research Station), where two other shrub species are under similar study design.