Methodology:

Sample collection of Alnus alnobetula and Salix spp. was undertaken in the Inuvialuit Settlement region during field campaigns in 2022, 2023, and 2024. The Inuvialuit Settlement region is one of the four regions of Inuit Nunangat, and part of the Northwest Territories, Canada.

Data collection was undertaken within the wider Beavers and Socio-ecological Resilience in Inuit Nunangat (BARIN) project collaborative environment - which adhered to CARE principles including contributing to advancing Inuit governance in research according to the National Inuit Strategy on Research priority areas. Collaboration with Indigenous experts underpinned the project including Inuit co-development and management of the project, and direct consultation with and co-investigation by the Fisheries Joint Management Committee and Joint Secretariat organisations. Relevant work permits were obtained for work on Inuvialuit private lands, as well as approval from local Hunters and Trappers Committees (HTCs) where updates were provided regularly at HTC board meetings. Via work with community researchers, knowledge was also regularly informally shared and informed the research process. Key project datasets are shared amongst all project partners and stored in ways that allow access and joint control for academic and Inuvialuit partners.

Shrub stems were sampled from both living erect canopy-forming shrubs, and from beaver-browsed stems. Collected shrubs were then subsampled into discs, and further split into subsamples of sufficient size for microslides. Subsamples were soaked in water for at least 24 hours prior to cutting of transverse sections with a GSL1-microtome to thickness of 10-20micrometeres. After sectioning, slides were then bleached, rinsed with milliQ water and double-stained with a 4:1 Safranin-Astrablue mixture. Sections were then rinsed sequentially with 50, 75 and 99% ethanol, before permanently fixing with Canada balsam under a cover slip, drying and stabilising in an oven at 60°C for a minimum of 12 hours.

Samples were digitised with a Canon EOS 750D DSLR mounted to a Leica DM 2000 compound microscope at 25x magnification. Individual images of thin sections or sanded sections were stitched into complete slide sections or cross-sections with PTGui (New House Internet Services BV, Rotterdam, NL) and Adobe Photoshop. SRWs were measured from resulting imagery using the open-source software ImageJ Fiji. The sampled willow shrubs commonly exhibited low to medium eccentricity in radial growth, with extensive tension wood, wedging or partially absent rings, occasional anatomical anomalies such as frost and blue rings, and a small number of samples with rings missing from individual cross sections. Therefore, careful cross-dating of each annual ring growth measurement to a corresponding calendar year was undertaken across the section and individual.

Growth curves between radii and cross-sections of the same individual were aligned via visual comparison, including utilising positive and negative pointer years (Schweingruber et al., 1990) and wood anatomical anomaly event years such as blue rings and frost rings. Missing rings were detected by careful examination across full cross-sections, and measurement and crossdating between four radii per cross-section. This enabled the identification of all annual rings within each cross-section and production of mean growth curves per individual which comprise this dataset. The measured SRW series are used for dendrochronological chronology formation and crossdating.

Data collection:

Instrumentation:

Canon EOS 750D DSLR

Leica DM 2000 compound microscope

Software:

PTGui

Adobe Photoshop

ImageJ Fiji

Data quality:

The raw ring width reference chronologies for Alnus and Salix exhibit significant overall interseries correlations and Expressed Population Signal greater than or equal to 0.85 for the common period represented by at least five individuals. Samples from browsed sites form floating chronologies with significant correlations with these reference chronologies.