Electronic supplementary Material
ESM 1 Cover-abundance values for eleven plant species estimated according to the
Braun-Blanquet method (Braun-Blanquet, 1928) modified by Dierschke (1994) at
Chamau (CHA) during the last year of the experiment (20-Apr-2011) before shelters
were installed (pre-treatment period). The species cover estimation was done at the
inner core area (2 x 1 m) in the center of each plot (3 x 3.5 m) for both treatments
(control vs. drought; n=3). The cover-abundance scale represents the combined coverabundance of one species as follows: r = rare, <1% cover; + = few (2 - 5) individuals,
≤1% cover; 1 = many (6 - 50) individuals, ≤5% cover; 2m = many (>50) individuals,
≤5% cover; 2a = any number of individuals, 5 - 15% cover; 2b = any number of
individuals, 16 - 25% cover; 3 = any number of individuals, 66 - 50% cover; 4 = any
number of individuals, 51 - 75% cover; 5 = any number of individuals, 76 - 100%
cover.
Species
Plots
Control
Replicate
Alopecurus pratensis
Arrhenatherum elatius
1
2
Drought
3
1
2
2a
3
2b
1
Bellis perennis
+
Festuca arundinacea
1
Lolium multiflorum
3
Phleum pratense
1
Poa pratensis
3
2m
2a
2a
+
5
5
5
1
1
5
5
Ranunculus repens
+
Taraxacum officinalis
+
1
+
2a
r
+
Trifolium repens
Veronica filiformis
1
+
+
1
+
1
ESM 2 Effects of simulated summer drought (2009 to 2010) on cover-abundance of
eleven species, estimated according to the Braun-Blanquet method (see ESM 1),
tested by a F-test referring to the linear mixed-effects model for the grassland site
Chamau (CHA). Braun-Blanquet cover-abundance values were transformed to
percentage species cover according to Dierschke (1994). Fixed effects were treatment
(control vs. drought) and species (see ESM 1). “Plot” (n = 3 ) was specified as
random effect. Significant differences (P ≤ 0.05) are formatted in bold.
Site
CHA
2
numDF
denDF
F value
P value
(Intercept)
1
41
86.473
Treatment
1
41
0.174
<.001
0.678
Species
10
41
53.855
<.001
Treatment:Species
10
41
1.15
0.3534
ESM 3 Mean relative proportion of belowground standing biomass (0-30 cm soil
depth) in 2011 at Chamau (CHA) and Alp Weissenstein (AWS). The samples were
stratified into three layers: 0-5 cm, 5-15 cm and 15-30 cm. Means and SD were
calculated using all sampling dates (CHA: n = 7, AWS: n = 6) when samples were
taken down to 30 cm (see Fig. 3). At each sampling date, n = 6 replicates were taken
at CHA and n = 5 replicates at AWS.
3
ESM 4 δ18O data of soil water (natural abundance) from different depths used for the
linear interpolation method (LI) to estimate depth of plant water uptake. If more than
three values exist, the ones used for the Baysian calibrated mixing model (top,
intermediate, deep; see also ESM 5) are marked with an arrow ( ). Data are given for
the two grassland sites Chamau (CHA) and Alp Weissenstein (AWS) for each year,
experimental period (pre-tmt, tmt, post-tmt period) and treatment (control vs.
drought). Standard deviations are given (2009: n = 3; 2010 and 2011: n = 4).
Note: The exclusion of rain during the tmt period resulted in a relatively depleted
isotopic composition of soil water at the drought plots compared to the control plots
receiving natural precipitations. This result reflects the seasonal shifts in the isotopic
composition of meteoric water, with relatively depleted rain during winter and
relatively enriched rain during summer (minimum/maximum δ18O values measured
between 2009-2011 at CHA: -22.5‰ / -1.7‰; at AWS: -20.9‰ / 0.1‰; for δ2H vs.
δ18O relationships for both sites, see Prechsl et al. 2014).
4
ESM 5 Overview of the δ18O data in soil and vegetation (mean±SE) for the two
grassland sites Chamau (CHA) and Alp Weissenstein (AWS) used for the Baysian
calibrated mixing model (SIAR). The δ18O values of soils were selected from the
entire δ18O soil profile used in the linear interpolation method (LI), while the
vegetation δ18O values are used in both approaches, LI and SIAR (see also ESM 4).
Data are given for each year, experimental period (pre-tmt, tmt, post-tmt period) and
treatment (control vs. drought).
δ 18O [‰]
Plant
community
Soil layer
Site
Year
Period
CHA
2009
pre-tmt
1-May-2009
tmt
6-Aug-2009
post-tmt
2-Oct-2009
pre-tmt
29-Apr-2010
2010
2011
Date
tmt
31-Jul-2010
post-tmt
10-Sep-2010
pre-tmt
20-Apr-2011
tmt
7-Jun-2011
post-tmt 12-Aug-2011
AWS
2010
2011
pre-tmt
3-Jul-2010
tmt
19-Aug-2010
post-tmt
15-Sep-2010
pre-tmt
21-Jun-2011
tmt
11-Aug-2011
post-tmt 29-Aug-2011
5
Treatment
Top
Intermediate
Deep
control
drought
control
drought
control
drought
-11.9
-11.3
-6.2
-8.3
-4.6
-5.2
±
±
±
±
±
±
0.4
0.5
0.3
0.6
0.4
0.8
-12.4
-12.5
-7.0
-11.1
-5.8
-7.5
±
±
±
±
±
±
0.5
0.4
0.5
0.7
0.2
0.8
-13.1
-13.2
-8.0
-12.0
-7.6
-9.2
±
±
±
±
±
±
0.4
0.3
0.5
0.8
0.3
0.5
-11.5
-11.6
-7.2
-8.9
-6.0
-6.6
±
±
±
±
±
±
0.2
0.2
0.3
0.3
0.4
0.2
control
drought
control
drought
control
drought
-10.8
-10.3
-8.2
-10.7
-7.4
-7.8
±
±
±
±
±
±
0.5
0.6
0.5
0.2
0.3
0.3
-13.5
-13.1
-8.0
-11.5
-7.9
-9.1
±
±
±
±
±
±
0.5
0.2
0.3
0.4
0.3
0.2
-13.8
-13.5
-8.8
-12.2
-8.3
-9.9
±
±
±
±
±
±
0.6
0.6
0.3
0.3
0.3
0.3
-9.7
-10.6
-9.3
-10.9
-6.9
-7.6
±
±
±
±
±
±
0.3
0.3
0.3
0.3
0.1
0.2
control
drought
control
drought
control
drought
-9.2
-10.5
-6.5
-9.8
-6.0
-6.2
±
±
±
±
±
±
0.6
0.6
0.4
0.5
0.2
0.5
-12.2
-12.3
-8.9
-12.9
-6.8
-7.9
±
±
±
±
±
±
0.6
0.6
0.6
0.5
0.3
0.4
-11.8
-13.3
-10.8
-13.2
-6.9
-8.5
±
±
±
±
±
±
0.5
0.4
0.4
0.5
0.2
0.4
-11.4
-11.1
-8.2
-11.4
-6.4
-7.0
±
±
±
±
±
±
0.3
0.4
0.3
0.3
0.2
0.3
control
drought
control
drought
control
drought
-13.7
-14.3
-13.6
-13.6
-11.0
-11.3
±
±
±
±
±
±
1.1
0.8
0.3
0.3
0.4
0.5
-12.6
-13.3
-13.7
-14.7
-11.0
-12.4
±
±
±
±
±
±
1.0
0.4
0.2
0.4
0.3
0.4
-12.6
-14.0
-14.1
-15.8
-12.0
-14.1
±
±
±
±
±
±
0.6
0.9
0.2
0.3
0.5
0.6
-12.3
-12.2
-14.2
-15.9
-11.2
-10.7
±
±
±
±
±
±
0.3
0.3
0.2
0.3
0.3
0.2
control
drought
control
drought
control
drought
-9.1
-8.8
-7.9
-9.1
-6.2
-5.4
±
±
±
±
±
±
0.4
0.3
0.2
0.4
0.5
0.5
-9.5
-9.7
-8.6
-13.5
-8.5
-11.5
±
±
±
±
±
±
0.3
0.2
0.2
0.4
0.4
0.8
-11.7
-11.3
-9.1
-15.0
-8.7
-15.3
±
±
±
±
±
±
0.6
0.6
0.4
0.4
0.3
0.4
-9.7
-10.5
-8.4
-13.1
-6.8
-9.0
±
±
±
±
±
±
0.4
0.3
0.2
0.3
0.2
0.3
ESM 6 Effects of simulated summer drought on water uptake depths as calculated by
linear interpolation (LI) for the three individual experimental periods (pre-tmt, tmt,
post-tmt period). Effects were tested by a F-test referring to the linear mixed-effects
model with “plot” (CHA: n = 14; AWS: n = 10) specified as random effect. The LME
only included significant fixed effects and interactions from the overall model (Table
4) for the two sites Chamau (CHA) and Alp Weissenstein (AWS), i.e. treatment
(control vs. drought) and year (CHA: 2009-2011, AWS: 2010 and 2011) and their
interactions. Significant differences (P ≤ 0.05) are formatted in bold.
Site
CHA
Period
pre-tmt
tmt
post-tmt
AWS
pre-tmt
tmt
post-tmt
6
numDF
denDF
F value
P value
(Intercept)
1
16
81.840
<.001
Treatment
1
10
0.018
0.895
Year
2
16
0.153
0.859
Treatment:Year
2
16
0.752
0.487
(Intercept)
1
13
278.230
<.001
Treatment
1
11
38.047
<.001
Year
2
13
4.177
0.040
Treatment:Year
2
13
7.026
0.009
(Intercept)
1
15
87.767
<.001
Treatment
1
11
0.025
0.878
Year
2
15
5.550
0.016
Treatment:Year
2
15
0.285
0.756
(Intercept)
1
6
28.022
0.002
Treatment
1
6
0.781
0.411
Year
1
5
103.166
<.001
Treatment:Year
1
5
1.275
0.310
(Intercept)
1
8
77.729
<.001
Treatment
1
8
1.009
0.345
Year
1
6
3.233
0.122
Treatment:Year
1
6
<.001
0.981
(Intercept)
1
6
40.054
<.001
Treatment
1
6
0.002
0.962
Year
1
6
10.093
0.770
Treatment:Year
1
6
11.850
0.014
References
Braun-Blanquet J (1964) Pflanzensoziologie, Grundzüge der Vegetationskunde, 3rd
ed. Springer, Wien-New York
Dierschke H (1994) Pflanzensoziologie. Eugen Ulmer Verlag, Stuttgart
Prechsl UE, Gilgen AK, Kahmen A, Buchmann N (2014) Reliability and quality of
water isotope data collected with a low-budget rain collector. Rapid Commun
Mass Spectrom 28:879-885
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