Table S1. Monthly and annual mean canopy temperature (°C) for Erman’s birch growing along an altitudinal
gradient on the north-facing slope of Changbai Mountain.
Altitude
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1400
−16.5
−13.9
−10.4
−2.8
3.2
11.4
14.6
15.0
10.0
2.9
−7.7
−14.8
1600
−17.0
−15.1
−11.8
−5.5
0.9
9.2
12.7
13.8
8.4
1.4
−8.5
−15.4
−2.2
1800
−17.5
−15.9
−12.7
−7.6
−0.5
8.5
12.1
12.9
8.1
0.7
−8.8
−15.9
−3.0
1900
−17.3
−15.7
−12.5
−7.7
−0.7
8.3
12.0
13.0
8.2
0.7
−8.6
−15.7
−3.0
2000
−17.6
−16.1
−12.8
−8.2
−1.1
8.0
11.7
12.6
7.8
0.4
−8.8
−16.1
−3.4
2100
−17.4
−15.9
−12.5
−7.5
−0.6
8.1
11.7
12.5
7.7
0.4
−8.6
−15.9
−3.2
(m a.s.l.)
Annual
Note: Unit of air temperature (°C).
Table S2. Annual average soil temperature (10 cm-depth) and length of growing season.
Altitude (m a.s.l.)
Indicators
1600
1800
1900
2000
2100
10 cm-depth soil temperature (°C)
9.4
9.8
8.2
7.8
8.6
Length of growing season (days)
142
137
131
128
118
Note: The beginning of the growing season was defined as the date at which the weekly mean soil
temperatures in the shade at 10 cm depth first exceeded 0 °C, and the end of the growing season as the date at
3 4
0
1 2
Density
5 6
7
which the weekly mean canopy air temperatures first dropped below 0 °C.
0.0
0.2
0.4
0.6
0.8
Volumetric water content (%)
Figure S1. Soil volumetric water content (VWC %) in ten plots in the treeline ecotone (n = 170 samples) on the
north slope of Changbai Mountain.
1
Volumetric water content (%)
Soil depth
10
20
40
30
20
10
1950
2000a 2000b 2000c 2000d
2050
Micro-sites
Figure S2. Micro-site effects on soil volumetric water content (VWC %) in 10 cm and 20 cm depth along an
altitudinal gradient on the north-facing slope of Changbai Mountain. Soil moisture was greatly affected by soil
depth, VWC at 20 cm-depth was much higher than that at 10 cm-depth, whereas, no significant difference was
detected within altitudes.
Figure S3. Presence of flag-shaped and supine Erman’s birches at 1800 m (a.s.l.) indicates high wind speed at
this altitude.
2
(a)
(b)
Figure S4. Distribution patterns of Erman’s birch associated with snow cover in mid-winter (a) and microtopography (b).
3
sapling
N
moisture
C
snowdepth
0
0
RDA2
5
10
P
total
upright.and.tall
C:N N:P
-5
upright
pH
-10
shrubby.and.tall
shrubby
0
5
10
15
20
RDA1
Figure S5. Abundance of Erman’s birch with different tree form classes in relation to soil properties (C—total
carbon, N—total nitrogen, P—total phosphorus, C:N—the ratio of C to N, and N:P—the ratio of N to P) and
snow depth, assessed with Redundancy Analysis (RDA). Abundance of saplings displayed a high correlation
with snow depth.
4