Electronic Supplementary Material
Enhanced Precipitation Variability Effects on Water Losses and Ecosystem Functioning:
Differential Response of Arid and Mesic Regions
Osvaldo E. Sala1,2,3,*, Laureano A. Gherardi1,3, Debra P.C. Peters3,4
1
School of Life Sciences, Arizona State University, Tempe, AZ, 85287-4501, USA
2
School of Sustainability, Arizona State University, Tempe, AZ, 85287-4501, USA
3
Jornada Basin Long Term Ecological Research Program, New Mexico State University, Las
Cruces, NM, 88003, USA
4
USDA-ARS, Jornada Experimental Range, Las Cruces, NM 88003, USA
*
Corresponding author: Osvaldo Sala, Ph 480-965-4120, Fax 480-727-7584 Email address
Osvaldo.Sala@ASU.edu
1
S1 Relationship between annual ambient precipitation and the precipitation for all the sites
and all the treatments for the experimental 100-year period. Most of the points fall on or
close to the 1:1 line indicating that the experimental modification of variability did not modify
the mean.
2
S2 Effects of precipitation variability and its scale on plant transpiration, soil evaporation,
deep percolation and soil water availability for 35 locations along a gradient of mean
annual precipitation. a-c plant transpiration (cm yr-1), d-f soil evaporation (cm yr-1), g-i deep
percolation(cm yr-1) and j-l soil water availability (number of days per year when average soil
water potential was greater than -1 MPa). a,d,g,j show results of changes in inter-annual
variability enhanced precipitation at the 1-year scale; b,e,h k show results of enhanced
precipitation at the 9-year scale and c,f,i,l show results at the 12-year scale. Each data point
represents one of the 35 locations for each treatment and lines regression lines per treatment.
Control (black dots and line), enhanced precipitation variability by 25% (green), 50% (blue) and
75% (red). Slope of each model is indicated as b and R squared values correspond to overall
ANCOVA R squared for each variable at each variability scale. Different letters associated with
the slopes indicate significant (p <0.05) differences versus control.
3
4
Table S2a Results for statistical analyses of mean transpiration and evaporation as a function of mean annual precipitation
across increased variability treatments.
Transpiration
Evaporation
Intra-annual variability
Slope
SE
t-value
P
Slope
SE
t-value
P
Model Intercept
-2.523
1.63
-1.55
0.124
19.616
1.37
14.27
< 0.001
Control
0.434
0.03
13.75
< 0.001
-0.144
0.03
-5.39
< 0.001
25%
-0.002
0.05
-0.05
0.959
0.003
0.04
0.08
0.935
50%
-0.008
0.05
-0.19
0.852
0.013
0.04
0.35
0.725
75%
-0.007
0.05
-0.15
0.885
0.03
0.04
0.79
0.43
Contrasts of treatments to control
Model: R2 = 0.85, F(7,132) = 106.4, P < 0.001.
Model: R2 = 0.43, F(7,132) = 14.42, P < 0.001.
Model Intercept
-2.523
1.59
-1.58
0.116
19.616
1.26
15.55
< 0.001
Control
0.434
0.03
14.05
< 0.001
-0.144
0.02
-5.87
< 0.001
25%
-0.029
0.04
-0.67
0.504
0.005
0.04
0.16
0.875
50%
-0.104
0.04
-2.39
0.018
0.017
0.04
0.49
0.628
75%
-0.176
0.04
-4.03
< 0.001
0.023
0.04
0.67
0.502
1-year inter-annual variability
Contrasts of treatments to control
Model: R2 = 0.81, F(7,132) = 79.03, P < 0.001.
5
Model: R2 = 0.52, F(7,132) = 20.29, P < 0.001.
3-year inter-annual variability
Model Intercept
-2.523
1.61
-1.57
0.118
19.616
1.29
15.21
< 0.001
Control
0.434
0.03
13.95
< 0.001
-0.144
0.03
-5.75
< 0.001
25%
-0.036
0.04
-0.81
0.418
0.004
0.04
0.11
0.912
50%
-0.126
0.04
-2.85
0.005
0.013
0.04
0.38
0.705
75%
-0.203
0.04
-4.61
< 0.001
0.019
0.04
0.53
0.595
Contrasts of treatments to control
Model: R2 = 0.80, F(7,132) = 73.76, P < 0.001.
Model: R2 = 0.51, F(7,132) = 19.58, P < 0.001.
Model Intercept
-2.523
1.63
-1.55
0.123
19.616
1.31
14.94
< 0.001
Control
0.434
0.03
13.78
< 0.001
-0.144
0.03
-5.65
< 0.001
25%
-0.036
0.05
-0.82
0.416
0.003
0.04
0.08
0.935
50%
-0.129
0.05
-2.89
0.004
0.01
0.04
0.27
0.789
75%
-0.207
0.05
-4.64
< 0.001
0.014
0.04
0.39
0.696
6-year inter-annual variability
Contrasts of treatments to control
Model: R2 = 0.79, F(7,132) = 71.36, P < 0.001.
6
Model: R2 = 0.50, F(7,132) = 18.92, P < 0.001.
9-year inter-annual variability
Model Intercept
Control
Contrasts to control
25%
50%
75%
12-year inter-annual variability
Model Intercept
Control
Contrasts to control
25%
50%
75%
Slope
-2.523
0.434
Transpiration
SE
t-value
1.66
-1.52
0.03
13.46
P
0.132
< 0.001
-0.034 0.05
-0.75
0.452
-0.124 0.05
-2.72
0.007
-0.201 0.05
-4.41
< 0.001
Model: R2 = 0.79, F(7,132) = 68.86, P <
0.001.
-2.523
0.434
1.62
0.03
-1.56
13.80
0.122
< 0.001
-0.036 0.04
-0.81
0.418
-0.131 0.04
-2.94
0.004
-0.212 0.04
-4.76
< 0.001
Model: R2 = 0.79, F(7,132) = 71.38, P <
0.001.
7
Slope
19.616
-0.144
Evaporation
SE
t-value
1.33
14.80
0.03
-5.59
P
< 0.001
< 0.001
0.001 0.04
0.03
0.973
0.007 0.04
0.19
0.853
0.011 0.04
0.30
0.764
2
Model: R = 0.50, F(7,132) = 18.62, P <
0.001.
19.616
-0.144
1.31
0.03
14.94
-5.65
< 0.001
< 0.001
0.003 0.04
0.07
0.944
0.009 0.04
0.26
0.798
0.014 0.04
0.40
0.693
Model: R2 = 0.50, F(7,132) = 18.86, P <
0.001.
Table S2b Results of statistical analyses of deep percolation and soil water content as a function of mean annual
precipitation across increased variability treatments.
Percolation
Wet-soil days
Intra-annual variability
Slope
SE
t-value
P
Slope
SE
t-value
P
Model Intercept
-3.670
1.07
-3.43
0.001
-14.308
12.74
-1.12
0.264
Control
0.150
0.02
7.22
< 0.001
3.435
0.25
13.91
< 0.001
25%
0.004
0.03
0.13
0.898
-0.039
0.35
-0.11
0.912
50%
0.019
0.03
0.65
0.518
-0.162
0.35
-0.46
0.644
75%
0.054
0.03
1.84
0.069
-0.310
0.35
-0.89
0.377
Contrasts of treatments to control
Model: R2 = 0.67, F(7,132) = 39.04, P < 0.001.
Model: R2 = 0.84, F(7,132) = 103.02, P < 0.001.
Model Intercept
-3.670
1.24
-2.97
0.004
-14.308
10.77
-1.33
0.186
Control
0.150
0.02
6.25
< 0.001
3.435
0.21
16.45
< 0.001
25%
0.031
0.03
0.91
0.365
-0.248
0.30
-0.84
0.402
50%
0.117
0.03
3.46
0.001
-0.977
0.30
-3.31
0.001
75%
0.238
0.03
7.03
< 0.001
-1.592
0.30
-5.39
< 0.001
1-year inter-annual variability
Contrasts of treatments to control
Model: R2 = 0.81, F(7,132) = 79.2, P < 0.001.
8
Model: R2 = 0.85, F(7,132) = 104.19, P < 0.001.
3-year inter-annual variability
Model Intercept
-3.670
1.30
-2.82
0.006
-14.308
10.41
-1.37
0.172
Control
0.150
0.03
5.93
< 0.001
3.435
0.20
17.02
< 0.001
25%
0.038
0.04
1.06
0.291
-0.235
0.29
-0.82
0.413
50%
0.139
0.04
3.91
< 0.001
-0.997
0.29
-3.49
0.001
75%
0.266
0.04
7.44
< 0.001
-1.703
0.29
-5.97
< 0.001
Contrasts of treatments to control
Model: R2 = 0.82, F(7,132) = 83.87, P < 0.001.
Model: R2 = 0.86, F(7,132) = 111.43, P < 0.001.
Model Intercept
-3.670
1.38
-2.66
0.009
-14.308
10.27
-1.39
0.166
Control
0.150
0.03
5.59
< 0.001
3.435
0.20
17.25
< 0.001
25%
0.048
0.04
1.26
0.21
-0.265
0.28
-0.94
0.349
50%
0.162
0.04
4.29
< 0.001
-1.084
0.28
-3.85
< 0.001
75%
0.297
0.04
7.85
< 0.001
-1.718
0.28
-6.10
< 0.001
6-year inter-annual variability
Contrasts of treatments to control
Model: R2 = 0.82, F(7,132) = 86.71, P < 0.001.
9
Model: R2 = 0.86, F(7,132) = 111.86, P < 0.001.
Percolation
Wet-soil days
9-year inter-annual variability
Slope
SE
t-value
P
Slope
SE
t-value
P
Model Intercept
-3.670
1.41
-2.60
0.01
-14.308
10.36
-1.38
0.169
Control
0.150
0.03
5.47
< 0.001
3.435
0.20
17.11
< 0.001
25%
0.053
0.04
1.38
0.171
-0.263
0.28
-0.93
0.357
50%
0.172
0.04
4.45
< 0.001
-1.011
0.28
-3.56
0.001
75%
0.311
0.04
8.02
< 0.001
-1.655
0.28
-5.83
< 0.001
Contrasts of treatments to control
Model: R2 = 0.82, F(7,132) = 88.25, P < 0.001.
Model: R2 = 0.86, F(7,132) = 111.45, P < 0.001.
Model Intercept
-3.670
1.38
-2.65
0.009
-14.308
10.25
-1.40
0.165
Control
0.150
0.03
5.59
0
3.435
0.20
17.29
0
25%
0.040
0.04
1.05
0.294
-0.223
0.28
-0.79
0.429
50%
0.149
0.04
3.93
0
-1.048
0.28
-3.73
0
75%
0.278
0.04
7.34
0
-1.737
0.28
-6.18
0
12-year inter-annual variability
Contrasts of treatments to control
Model: R2 = 0.81, F(7,132) = 80.39, P < 0.001.
10
Model: R2 = 0.86, F(7,132) = 114.1, P < 0.001.