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Data used for to fit linear mixed-effect models (package lme4, R v. 3.2.3) to assess the effect of nitrogen addition, warmer 
temperatures and browsing intensity on Betula glandulosa leaves biomass (Table 2)
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*Protocol*

We conducted factorial manipulations of growing season temperature, soil nitrogen and browsing intensity over 5 years
(2009-2013) in a split-plot experimental design (Fig. 1). The design included two levels of nitrogen (with or without 
nitrogen addition) in primary plots (4 m x 24 m), and two levels of temperature (ambient and warmed) crossed with 3 levels 
of summer caribou browsing (control: 0%, moderate: 25% and heavy: 75% of available shoots stripped of their leaves) in 
1 m x 1 m quadrats in the center of secondary plots (4 m x 4 m). Each combination of treatments (12) was replicated in five
exclosures designed to exclude caribou (12 x 26 m with a 1.5 m fence; hereafter refers as blocks)  for a total of 60 secondary 
plots.

We harvested the aboveground biomass of B. glandulosa from the central portion of each of the secondary plots at the beginning
of the 2014 growing season, after 5 years of experiment. Samples were dried at 70 °C for 72 hours, and weighed to the nearest 
0.1 g using an electronic scale (Mettler Toledo SB16000, Mettler-Toledo International Inc., Columbus, OH, USA). We then sorted
the biomass of three randomly selected blocks (out of the five available) into woody and leafy biomass; leaves were weighed to
the nearest 0.0001 g using an electronic scale (Secura 224 1S, Sartorius AG, Germany) in order to partition the biomass 
response. 
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*Definitions of column headings*

A) block: Blocking factor. Each combination of treatments (12) was replicated in 3 exclosures designed to exclude caribou 
(12 x 26 m with a 1.5 m fence; hereafter refers as blocks)

Value B, C, D


B) fertilization: Fertilization treatment level

Value: N (with nitrogen addition) or S(without nitrogen addition)


C) temperature: Temperature enhancement treatment level

Value: H (warmed with open top chambers), L (ambient temperature)


D) browsing: Simulation of browsing by caribou treatment level

Value:0 (control: 0%), 1 moderate: 25% of available shoots stripped of their leaves) or 3 (heavy: 75% of available shoots stripped of their leaves)


E) plot_id: Exclusive ID of each secondary plot

Value: Concatenation of block|Fertilization|Temp|Browsing


F) individual: ID of individuals within a plot

Value: A to V

G) Biomass : Biomass of leaves of B. glandulosa from the central portion (1 m x 1 m quadrats) of each of the secondary plots 
(4 m x 4 m) at the beginning of the 2014 growing season, after 5 years of simulation

Value: g

H) ext: The mention "ext" flag individual that were rooted out of the plot although clearly physiologically related to those within the plot (layering).

I) notes: personal note from the main author