The survival of reindeer during winter, their period of greatest food stress, is largely dependent upon the abundance and accessibility of food in their pastures. In Northern Sweden this realised availability of forage is notably affected by snow conditions and the impacts of forestry on understorey in these pastures. Whilst these factors have been examined to some extent in isolation, their combined effect on overall forage availability has, to the best of our knowledge to date, not been studied.

In this study, vegetation surveys and analysis of snow conditions were undertaken in 16 forest stands at various stages of recovery from clear-cutting. The variation in abundance and growth of understorey species edible by reindeer, such as lichen, were noted as forest age increased. The barrier effect of ice lenses in snow during winter was also noted. Lichen biomass was significantly affected by a combination of stand age, understorey vegetation height, and lichen height. Soil disturbance from the processes of felling, and competition in the vegetation communities recovering from this disturbance were identified as key drivers of change in lichen biomass. Overall, clear-cut forests had some of the greatest prevalence of ice lenses in the snow column, and forage availability at these sites was up to 61 % less than in stands over 58 years in age.

Tree age was measuring according to dendrochronological procedures, using a Mattson No. 4. Increment Borer (Sorbus International, Somerset, UK). Canopy cover was measured using a spherical densiometer (Spherical Crown Densiometer, Convex Model A, Forestry Suppliers, USA.).

At each site vegetation surveys were undertaken in 10 replicates of 4 m² quadrats. Percentage cover of each species was visually estimated. Plant height was measured at five random points within each quadrat and averaged. In two of the 4 m² quadrats at each site, five quadrants of 0.01 m² were placed. Lichen cover, and height at three points, was noted. All lichen within the 0.01 m² quadrats was extracted, dried to a constant weight at 105 ^oC, and immediately cooled and weighed (Satorius M-prove, Satorius AG, Goettingen, Germany). All data was nested by site.

Snow pits were dug in November 2019, plus January and March 2020. Six pits were dug per site, each > 10 m distance from one another, with three within 0.5 m of a tree and three in open areas between the trees. At clear-cut sites, the six snow pits were randomly distributed.

In pits, snow depth was measured, alongside hardness of each layer within the snow column using the hand hardness test. All measurements were undertaken by the lead author. The thickness of each distinct layer was measured with a ruler. Snow of the hand hardness categories P, K and I (henceforth PKI) were regarded as impenetrable to reindeer. If greater than 1 % of the site showed signs of reindeer digging the site was classified as having cratering present, otherwise classified as cratering being absent. All data was nested by site.

Daily temperature data at Jokkmokk flygplats weather station was used for winters starting 2006 until the winter of 2019/20, alongside daily snow depth data during the same period at Murjek D weather station. Winter was defined as 1^st October to 20^th April corresponding to the period when reindeer are allowed to be present in their winter grazing grounds.

Data were nested by site to avoid pseudoreplication.

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