Limited decadal growth of mountain birch saplings has minor impact on surrounding tundra vegetation

The study addresses two important issues in arctic treeline dynamics: • How do birch saplings, being the dominant treeline species, that have been established above treeline perform? • How do these birch saplings affect the surrounding tundra vegetation? For this, we collected species abundance measurements in 50 x 50 cm plots around birch saplings above the treeline near the Latnjajaure Field Station in northern Sweden. We compared these measurements with control measurements, and reference measurements taken below the treeline. We also looked at the growth (Diameter + Length) of birch saplings over 15 years (2001-2016). The data deposited includes the raw data, code, and statistical models used to analyze the data, and all output (figures and tables) used in the study. Further metadata can be found in the README file included with the data. GENERAL INFORMATION 1. Title of Dataset: Limited decadal growth of mountain birch saplings has minor impact on surrounding tundra vegetation 2. Author Information A. Principal Investigator Contact Information Name: Ruud Scharn Institution: University of Gothenburg Email: ruud.scharn@gu.se B. Associate or Co-investigator Contact Information Name: Robert Björk Institution: University of Gothenburg Email: robert.bjork@gu.se 3. Date of data collection: 2016-07-(4-31) 4. Geographic location of data collection Latnjajaure field station close to Abisko northern Sweden (68.35°N, 18.49°E). DATA & FILE OVERVIEW The file birch_coordinates.csv contains the coordinates of each birch (WGS84 and SWEREF99) together with height, number of stems, base diameter and number of branches. For each analysis in the paper, we created a folder containing three subfolders The main folders: 1 alpha diversity altitude slope 2 alpha diversity intercept only 3 Beta diversity 4 Diameter and length Subfolders are structured the same for all main folders containing: 1 input: containing raw input data. 2 script: R Script containing all data processing as well as the JAGS script containing the code used in the statistical modelling. R Scripts should run provided the path to the input data is set correctly (see setwd in the start of the script) and the required libraries are installed locally 3 output: containing output tables and figures Raw data for main folders 1-3 are the same containing: Latnja2006-16.txt: a tab-separated matrix containing species cover estimates (columns) for plots (rows). rownames contain community type (Bpt_Ref, Bpt and C for Reference, Birch and Control plots) and the height of the plot in meters above sea level. norway_latnjatree.dated.tre: dated phylogeny by scharn et al 2021 (doi: https://doi.org/10.1088/1748-9326/abfe8aOpens in a new tab) used for phylogenetic diversity estimates in Newick format. main folder 3 (Beta_diversity) sub-folder input contains netMPD_sweden.rds, a serialized R object file containing the mean pairwise distances of the species. main folder 4 contains: Birch_heigh_Diameter.csv: a tab-separated matrix containing the birch number, sampling year, height, and diameter Birch_heigh_Diameter_dif.csv: a tab-separated matrix containing the birch number, as well as the between year difference in height and diameter METHODOLOGICAL INFORMATION 1. Description of methods used for collection/generation of data: Methods can be found in "Limited decadal growth of mountain birch saplings has a minor impact on surrounding tundra vegetation" (See associated publication)