Climate change is most pronounced at high latitudes, where plant and animal populations are often strongly influenced by environmental fluctuations related to climate and weather. Environmental conditions can co-fluctuate over large distances and thereby synchronise primary production in space. However, large-scale studies of such spatiotemporal patterns remain rare in the Arctic, where short time-series and poor spatial replication have characterised the data available on both biotic and abiotic parameters. Here, we use dendrochronological tools to measure ring growth of a dominant dwarf shrub, the polar willow (Salix polaris Wahlenb.), previously found to reliably trace community-level vascular plant biomass production. We investigated climate drivers of vegetation growth and their role in the synchronisation of primary production across the rapidly warming archipelago of Svalbard (n = 8 sites, composed of 17 sub-sites, 0.06-293 km apart). We found contrasting effects of summer versus winter weather on ring growth and its spatial synchrony. Although an overall positive effect of summer temperature caused spatially synchronous growth, negative impacts of winter rain-on-snow events occurred only locally, potentially counteracting such synchrony. However, the anticipated increase in both summer temperature and spatial extent of rain-on-snow events, causing basal ice encapsulation of the vegetation, could change the relative importance of seasons for spatiotemporal dynamics of shrub growth. Because these shrub ring growth chronologies reflect annual fluctuations in total vascular plant biomass, fuelling the bottom-up controlled food-web, these results have large implications for our understanding of how climate change shapes tundra ecosystem productivity in time and space.

See the method section of the corresponding article doi:10.1111/oik.07059

Please read the ReadMe file before to download the data. 

A R script is available on request: mathilde.lemoullec@ntnu.no. 

File description for manuscript Le Moullec et al. 2020 Oikos: doi: 10.1111/oik.07059

# 1. Files to build chronologies .rwl

- rwl_petuniabukta.rwl   # rwl file from Salix polaris chronologies (at the plant level) published in Buchwal et al. 2013. Polar Biol.
- rwl_Semmeldalen.rwl  # rwl file from Salix polaris chronologies (at the cross-section level) published in Le Moullec et al. 2019 JEcol
- rwl_svalbard_new.rwl  # rwl from 6 new sites, 30 Salix polaris individual chronologies (at the cross-section level) 
- plant_info.txt               # Cross section's radius and ring to pith information of file "rwl_svalbard_new.rwl", for possible standardization e.g. BAI, RCS

# 2. Ring-growth information at the plant level formatted for linear mixed-effect models or synchrony analysis. 
- Salix_ind_BAIrcs_RAWpetunia_MeanCenter # Individual shrubs' RWI (standardized = BAI + RCS + Mean Centered).                                                                                                                                                                    # NOTE that ring growth from Petuniabukta are ONLY Mean Centered

- Salix_ind_RAW # Individual shrubs' raw ring width (micrometers)

# 3. Climate data 
- climat_raw_Oikos         # Raw climate data for each station used across Svalbard, provided by eKlima.no (except Hornsund).                                                                                                                        # Hornsund: data provided by the Institute of Geophysics Polish Academy of Sciences and meteorological staff of the Polish Polar Station Hornsund 
- climat_estimated_Oikos # Each climate variable is an estimate at the Svalbard scale: from a linear mixed-effect models with (1|Station) as random effect
- climat_estimated.se_Oikos # Standard error of the climate estimates "climat_estimated_Oikos"

# 4. GPS coordinates for distance matrix
- site_GPS     # Each Salix polaris' subsite UTM coordinates