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

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

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

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

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

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

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

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

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

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

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

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

# Tree-ring measurement <br>
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 <br>
sections were averaged per shrub for shrub level datasets (omitting the aboveground shiits due to low number of rings) <br>
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) <br>
.rwl files can be inspected in notepad <br><br>

# Scripts <br><br>

1. script_detrending_chrono.R was used for the following datasets: <br><br>

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

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

- reference_Endalen_shrublevel to produce a baseline site chronology <br><br>

this script also produced the chronology plots and chronolgy tables <br><br>

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

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