Alsos et al., 1998 Skarpe & van der Wal, 2002 Fox & Bergersen, 2005 Post & Pederson, 2008 Rinnan et al., 2009 Evju et al., 2010). Several experimental studies have used open top chambers (OTCs) or cloches to investigate the effects of climate warming on the phenology and growth of Arctic plant communities, both with and without nutrient supplementation (Robinson et al., 1998 Arft et al., 1999 J onsd ottir et al., 2005b Hollister et al., 2005a,b) The effects of grazing on these communities by vertebrates such as reindeer and geese are also relatively well documented (e.g. Despite the challenges of constructing ring growth chronologies from irregularly growing arctic shrubs, our findings confirm that shrub dendrochronology can open new opportunities for community‐dynamic studies under climate change, including in remote places where annual field sampling is difficult to achieve. Here we showed that ring growth indeed was a robust proxy for the annual above‐ground productivity of both the focal shrub and the vascular plant community as a whole. Fundamental to such applications is the assumption that annual ring growth reflects between‐year variation in above‐ground biomass production. Dendrochronological tools are increasingly used on arctic shrubs to enhance our understanding of vegetation dynamics in the world's most rapidly warming biome. The results suggest that ring growth measurements performed on this dominating shrub can be used to track fluctuations in past vascular plant production of high‐arctic tundra. As for above‐ground biomass, summer temperature was the main driver of ring growth, with this ecological signal becoming particularly clear when accounting for plant, site and habitat heterogeneity. polaris (r = 0.56) and the vascular plant community as a whole (r = 0.70). 3.Annual ring growth was positively correlated with above‐ground biomass production of both S. We established annual ring growth time‐series using linear mixed‐effects models and related them to local weather records and 13 years of above‐ground biomass production in six habitats. polaris shrubs across five sites in each of two habitats. 2.Using a balanced design in permanent plots for plant biomass monitoring, we collected 30 S. Taking advantage of a unique ground‐based monitoring time‐series of annual vascular plant biomass in high Arctic Svalbard (78°N), we evaluated how well retrospective ring growth of the widespread dwarf shrub Salix polaris represents above‐ground biomass production of vascular plants. ‘tree‐rings’) actually reflects primary production above‐ground remains unknown. Yet, high‐latitude plant species are subject to strong energy allocation trade‐offs, and whether annual allocations to secondary growth (e.g. Dendrochronological tools are increasingly used instead, particularly in the Arctic – the world's most rapidly warming biome. polaris leads to a sizeable decrease in food quantity and, possibly, to a limited increase in food quality.ġ.Long time‐series of primary production are rarely available, restricting our mechanistic understanding of vegetation and ecosystem dynamics under climate change. polaris responds to summer browsing the previous year by allocating resources to compensatory growth rather than to defence. Salix polaris showed little variation in the response to simulated browsing with local variation in resource availability (length of growing season) or with time of browsing. There was no increase in phenolics but a tendency to an increase in N content in the leaves of S. Leaf numbers, total and individual biomass of leaves, and the number of inflorescences were greatly reduced the year after treatment. polaris from areas with relatively short, intermediate, and long growing season, and their responses 1 yr after simulated browsing in early, mid, and late summer. We compared leaf characteristics and flowering of S. Salix polaris is browsed by Svalbard reindeer, and its response to browsing may influence subsequent utilization. We studied the response to simulated browsing by the deciduous dwarf shrub, Salix polaris, on high Arctic Spitsbergen. Plants respond to herbivory either by maximizing resource acquisition and compensatory growth or by minimizing loss of resources, e.g., by investing in chemical or structural defence.
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