1
2
Appendix 1: Data of survival time during drought from drought mortality experiments, for model
validation.
3
4
5
6
7
8
9
10
11
12
13
14
We validated the likelihood of simulations made under the three hypothesis by using the relationship
between the time to shoot death and embolism resistance measured on different species. We
reanalyzed four publications that had monitored the shoot death of seedlings or saplings in drought
mortality experiments. One study was performed on gymnosperm species only 1 and three other studies
were performed on angiosperm species 2–4. In total, we collected data for 15 species. All these
experiments were made under semi-controlled conditions on potted seedlings or saplings. The death of
leaves and shoots was recorded at different times since the beginning of an experimentally imposed
drought. Here we used the time required to reach the death of 50% of the individual (T50) after the
beginning of the drought treatment as an indicator of survival time during drought. This data was not
always available from the published papers and we are grateful to Steven Jansen, Shan Li and Tim
Brodribb who provided us the data on our request. We found a significant relationship between t 50 and
ψ50 for angiosperms and gymnosperms separately (Figure A1-1).
15
16
17
Figure A1-1: Time to reach shoot death (t50) as a function of embolism resistance (ψ50) for angiosperms (a) and
gymnosperms (b)) derived from drought mortality experiment. In the panel (a, for angiosperms) data are from Urli
18
19
20
21
22
et al (2013); Barigah et al (2013); Li et al (2015). The fitted relationship is T 50=7-11x ψ50; the R² is 0.51 and the
slope of the linear relationship is significantly different from 0 (P value=0.015). In the panel (b, for gymnosperms); data
are from Brodribb & Cochard 2009. The fitted relationship is T 50=3-2.4x ψ50; the R² is 0.85 and the slope of the
linear relationship is different from 0 with P value=0.075. For angiosperms, Fagus sylvatica was measured in two
different experiments2,3, the two values were thus averaged.
23
24
25
26
27
28
29
30
31
32
33
In each experiments identical soil volume and climate were used across species. However, there were
differences in relative air humidity and soil volume across experiments (both of them can strongly affect
the survival time during a water deficit episode), particularly between the gymnosperm experiment and
all angiosperm experiments. This precluded the direct comparison of the survival time across the four
different studies. We therefore assessed whether the relationship between T50 and ψ50 was affected by
differences in soil volume or air relative humidity. For each individual experiment we computed the slope
of the relationship between t50 and ψ50 and tested if it was related to soil volume and air humidity
reported in the materials and methods of each study. We indeed found a relation between the slope and
both the soil volume and average relative humidity across the four experiments (Figure A1-2), that were
particularly due to the difference between angiosperm experiments and the experiment on
gymnosperms (red square in Figure A1-2).
34
35
36
37
38
Figure A1-2 : Slope of the linear relationship of the T50 versus P50 relationships (computed for each experiment
individually) versus the pot size and relative humidity during the experiments. Black circles are for angiosperm
experiments and the red square is for the gymnosperm experiment.
39
40
41
42
43
To overcome this issue, we computed a normalized T50 by dividing the measured T50 value of each
species by the slope of the T50 versus ψ50 relationship of the corresponding experiment. For the sake of
clarity data presented in the main manuscript (Figure 2a) were expressed relative to the maximum
standardized T50 value. The following Table A1-1 presents row data as well standardized data for each
species that were used to build Figure 2C of the main manuscript.
Table A1-1: Embolism resistance (ψ50) and survival time (time to reach shoot death T50) in drought
mortality experiments of different species that was used to build Figure 2a of the main manuscript. The
procedure used to normalize the data of T50 is described in the above text.
Group
Species
Dacrycarpus
Gymnosperm dacrydioides
Lgarostrobos
Gymnosperm franklinii
Slope of the t50
ψ50 (Mpa) T 50 (days)
versus P50
relationship
Normalized
T 50
Normalized
and
relativized
T 50
Publication
-10,1
23
2,4
9,6
0,7
Actinostrous
Gymnosperm arenarius
Angiosperm Populus tremula
-10,6
-2,6
32
44
2,4
9,7
13,3
4,5
1,0
0,3
Brodribb & Cochard
2009
Brodribb & Cochard
2009
Brodribb & Cochard
2009
Brodribb & Cochard
2009
Urli et al 2013
Angiosperm
Angiosperm
Angiosperm
Quercus robur
Quercus pubescens
Quercus ilex
-4,8
-5,5
-7
55
75
85
9,7
9,7
9,7
5,7
7,7
8,8
0,4
0,6
0,7
Urli et al 2013
Urli et al 2013
Urli et al 2013
Angiosperm
Angiosperm
Angiosperm
Populus deltoides
Fagus sylvatica
Fagus sylvatica
-1,5
-3,2
-3,2
40
70
72,5
19
19
19
2,1
3,7
3,8
0,2
0,3
0,3
Barigah et al 2013
Barigah et al 2013
Barigah et al 2013
Angiosperm
Angiosperm
Angiosperm
Acer pseudoplatanus -2,9
Corylus avellana
-2,1
Fraxinus excelsior
-2,7
16,7
12,6
17,8
12,9
12,9
12,9
1,3
1,0
1,4
0,1
0,1
0,1
Li et al 2015
Li et al 2015
Li et al 2015
Angiosperm
Angiosperm
Acer campestre
Carpinus betulus
40
49
12,9
12,9
3,1
3,8
0,2
0,3
Li et al 2015
Li et al 2015
Gymnosperm
Callitris rhomboidea
-2,1
5,25
2,4
2,2
0,2
-3,574
15,8
2,4
6,6
0,5
-4,8
-3,8
REFERENCES
1.
Brodribb, T. J. & Cochard, H. Hydraulic failure defines the recovery and point of death in waterstressed conifers. Plant Physiol. 149, 575–84 (2009).
2.
Urli, M. et al. Xylem embolism threshold for catastrophic hydraulic failure in angiosperm trees.
Tree Physiol. 1–12 (2013). doi:10.1093/treephys/tpt030
3.
Barigah, T. S. et al. Water stress-induced xylem hydraulic failure is a causal factor of tree
mortality in beech and poplar. Ann. Bot. 112, 1431–1437 (2013).
4.
Li, S. et al. Leaf gas exchange performance and the lethal water potential of five European
species during drought. Tree Physiol. tpv117 (2015). doi:10.1093/treephys/tpv117