Tree-ring growth of S polaris on Svalbard under baseline conditions and artificially enhanced summer rainfall

# Data
Tucson format .rwl files (unit = 1/100mm) for three salix polaris tree-ring records from Svalbard.
- Location2_sections.rwl
- Location2_shrublevel.rwl
- Location5_sections.rwl
- Location5_shrublevel.rwl
- reference_Endalen_shrublevel.rwl

Site chronologies derived from tree-ring data
- chronology_loc2_new.csv
- chronology_loc5_new.csv
- chronology_Endalen.csv

each chronology dataset contains:
- year
- std: standard chronology (detrended using age-dependent spline with 20-year rigidity)
- res: residual chronology (detrended using age-dependent spline with 20-year rigidity and corrected for first-order temporal autocorrelation)
- samp.depth (sample depth, nr of shrubs available for year, set to minimum of 3 years)

# Sites
2 - Adventdalen Polygonal Tundra
78.192°N, 15.862°E

5 - Ny-Alesund terrace along Westbyelva
78.920°N, 11.917°E

Endalen - A riverbed north of Endalselva
78.194°N, 15.793°E

# Experimental Design
Endalen is a reference site. 15 shrubs were sampled, the dataset contains
shrub-averaged ring widths from 7 of these shrubs

Location 2 and 5 are experimental sites in which some plots were subjected to rainfall additions through irrigation (see sample coding)
"I" plots received enhanced rainfall in 2022
"ES" and "LS" plots received enhanced rainfall in 2023.
See Magnússon et al. (2024) and associated data for site characterizations, treatment information, plot coordinates and plot environmental conditions
Paper: https://doi.org/10.1016/j.scitotenv.2024.173696
Data: https://doi.org/10.17026/dans-23v-7hcg

# Sample coding
example shrub level (loc 2 & 5): 2ES3A
example sections (loc 2 & 5): 5LS4BR

These samples codes are built up as follows:
- first digit = location (2 or 5)
- followed by treatment code of one or two digits, where:
- c = control (no extra rain
- i = 50mm extra rainfall in late summer 2022
- es = 50mm extra rainfall in early summer 2023
- ls = 50mm extra rainfall in late summer 2023
- followed by a value A-I indicating the position within the plot (see Magnússon et al., 2024)
- for section level data, followed by section code (C = collar, R = root, S = belowground shoot)

for the endalen shrublevel samples, the sampled shrubs were simply named S1 - s15.

# Tree-ring measurement
sections averages of root segments (below root collar), root collar (assumed oldest part of shrub, root-shoot transition), belowground shoot and aboveground shoot ('shoot-end') , based on three, sometimes 2 radii per section
sections were averaged per shrub for shrub level datasets (omitting the aboveground shiits due to low number of rings)
Software: LASX 4.13 for sample digitization, Coorecorder 9.0 for tree-ring measuement along radii, CDendro for averaging and crossdating of radii to section level (_sections) and to shrublevel (_shrublevel)
.rwl files can be inspected in notepad

# Scripts

1. script_detrending_chrono.R was used for the following datasets:

- Location2_shrublevel to produce a baseline site chronology (excl. I plots from 2022 onwards and ES and LS plots from 2023 onwards)
- Location2_sections to produce section level RWI
- Location2_shrublevel to produce shrub level RWI

- Location5_shrublevel to produce a baseline site chronology (excl. I plots from 2022 onwards and ES and LS plots from 2023 onwards)
- Location5_sections to produce section level RWI
- Location5_shrublevel to produce shrub level RWI

- reference_Endalen_shrublevel to produce a baseline site chronology

this script also produced the chronology plots and chronolgy tables

2. script_climgrowth was applied to all three chronologies for a stand ard minimum available time period from 2003 onwards
this script produced the climate-growth bar plots

3. script_treatment was used on section- and shrub-level detrended RWI data for locations 2 and 5.
this script produced the mixed modelling and posthoc tables and treatment effect bar & jitter plots