1
Supporting Information
2
3
Characterizing differences in precipitation regimes of extreme wet and dry years: Implications
4
for climate change experiments
5
6
Alan K. Knapp1, David L. Hoover1, Kevin R. Wilcox1, Meghan L. Avolio2, Sally E. Koerner1,
7
Kimberly J. La Pierre3, Michael E. Loik4, Yiqi Luo5, Osvaldo E. Sala6, and Melinda D. Smith1
8
9
10
1
Colorado State University; 2University of Utah; 3University of California, Berkeley; 4University
of California, Santa Cruz; 5University of Oklahoma; 6Arizona State University
11
12
13
Corresponding author:
14
Alan K. Knapp
15
Graduate Degree Program in Ecology
16
Department of Biology
17
Colorado State University
18
Ft. Collins, CO 80526
19
Ph: 970 491-7010
20
Fax: 970-491-0649
21
aknapp@colostate.edu
22
23
1
24
Table S1. Model results from permutational multivariate analysis of variance (based on 999
25
permutations) testing for differences among extreme dry (annual precipitation in the 10th
26
percentile), extreme wet (annual precipitation in the 90th percentile), and average (between 45th
27
and 55th percentiles) years using normalized precipitation attributes from 12 weather stations in
28
each of 12 ecoregions.
Multi-comparisons
Main models
Ecoregion
df Pseudo-
Average vs
Average vs
Dry
Wet
P
t
P
t
P
Dry vs Wet
t
P
F
Savanna
2
117.39
<0.01
8.01
<0.01 8.52
<0.01 14.28
<0.01
Tropical/subtropical
2
desert
188.30
<0.01
9.72
<0.01 10.79
<0.01 17.99
<0.01
Mediterranean
2
115.76
<0.01
7.93
<0.01 8.02
<0.01 14.30
<0.01
Tropical/subtropical
2
steppe
166.51
<0.01
9.83
<0.01 9.79
<0.01 17.79
<0.01
Subtropical
2
140.46
<0.01
8.85
<0.01 8.68
<0.01 17.82
<0.01
Prairie
2
160.5
<0.01
9.45
<0.01 8.33
<0.01 17.20
<0.01
Marine
2
194.67
<0.01
9.04
<0.01 11.93
<0.01 18.58
<0.01
Subarctic
2
155.47
<0.01
8.45
<0.01 9.27
<0.01 17.95
<0.01
Warm continental
2
85.73
<0.01
6.52
<0.01 6.63
<0.01 12.78
<0.01
Temperate desert
2
152.06
<0.01
9.26
<0.01 8.40
<0.01 16.97
<0.01
Temperate steppe
2
127.87
<0.01
8.86
<0.01 8.38
<0.01 15.54
<0.01
Hot continental
2
126.68
<0.01
8.66
<0.01 7.80
<0.01 15.09
<0.01
29
30
31
32
2
30
Hot Continental
Marine
Mediterranean
NS
NS
20
10
0
10
20
Contribution to Divergence (%)
30
30
Prairie
Savanna
Subarctic
NS
20
10
0
10
20
30
30
Subtropical
Temperate Desert
Temperate Steppe
Tropical / Subtropical Desert
Tropical / Subtropical Steppe
Warm Continental
20
10
0
10
20
30
30
NS
NS
20
10
0
10
20
#
Ex
tre
m
e
Ev
Ev ent
en s
tS
iz
e
#
#
Ex Ev
tre ent
s
m
e
C
D
D
C
D
#
D
Ex
tre
m
e
Ev
Ev ent
en s
tS
iz
e
#
#
E
Ex
ve
tre
nt
s
m
e
C
D
D
C
D
#
D
Ex
tre
m
e
Ev
Ev ent
en s
tS
iz
e
#
#
Ex Ev
tre ent
s
m
e
C
D
D
C
D
D
30
Precipitation Regime Attribute
33
34
Figure S1. Percentage contribution of five precipitation regime attributes to divergence between
35
extreme wet and average years (blue panel) and extreme dry and average years (white panel) for
36
12 different terrestrial ecoregions. Precipitation regime attributes: number of extreme rainfall
37
events (99th percentile; # Extreme Events), average event size (Event Size), the number of
38
rainfall events (Event #), number of extreme (99th percentile) dry periods (# Extreme CDD), and
39
average length of dry period (CDD). Data were normalized independently for each station before
40
running SIMPER analysis. NS = values for these attributes not significantly different based on
41
mixed model ANOVAs.
3
42
Table S2. Results from one-way mixed model ANOVA for each precipitation attribute for the
43
each of the 12 ecoregion divisions. In each model, site was a random variable and the effect
44
tested was type of year (Wet, Average, Dry). Results are presented as in Table 1, and show F-
45
value and p-values for each year type x attribute ANOVA as well as mean values with standard
46
errors (SE). Precipitation regime attributes: the number of extreme (99th percentile) rainfall
47
events (# Extreme Events), average event size (Event Size), the number of rainfall events (Event
48
#), number of extreme (99th percentile) dry periods (Extreme CDD), and average length of dry
49
period (CDD).
Ecoregion
HOT CONTINENTAL
MARINE
MEDITERRANEAN
PRAIRIE
SAVANNA
SUBARCTIC
SUBTROPICAL
Precipitation Attribute
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
4
F-Value
201.8
106.6
178.7
29.8
76.1
185.5
371.1
169.0
68.3
54.1
101.1
159.7
176.1
17.1
47.8
170.1
174.0
116.9
57.5
66.2
180.8
169.7
130.2
11.0
53.7
220.4
184.8
44.7
53.3
90.3
159.3
p-value
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
Wet
Mean
5.2
134.3
9.6
1.9
3.5
6.0
192.7
9.4
1.8
3.3
4.2
91.7
12.7
1.8
8.2
4.0
95.1
11.1
1.5
5.6
4.1
73.3
20.9
1.8
9.4
6.6
156.0
4.8
2.1
3.2
4.8
SE
0.2
6.1
0.4
0.1
0.2
0.2
8.2
1.0
0.2
0.2
0.6
9.4
1.1
0.2
1.0
0.2
7.0
0.6
0.2
0.7
0.5
6.0
0.8
0.2
0.9
0.3
8.3
0.7
0.2
0.2
0.3
Average
Mean SE
3.0
0.3
124.4 6.1
7.9
0.4
2.3
0.2
3.7
0.2
3.1
0.2
163.3 8.2
8.0
1.0
3.2
0.2
3.8
0.2
1.8
0.6
76.2
9.5
9.7
1.1
1.8
0.2
9.2
1.0
1.9
0.3
80.0
7.1
8.9
0.6
2.0
0.2
6.5
0.7
1.6
0.5
58.6
6.0
14.6
0.8
2.0
0.2
11.0
0.9
3.9
0.3
136.1 8.3
4.3
0.7
3.2
0.2
3.7
0.2
2.2
0.3
Dry
Mean
1.4
104.7
6.8
3.5
4.3
1.4
132.5
6.4
4.1
4.7
0.5
59.1
7.1
2.6
11.6
0.7
61.5
7.1
3.3
8.9
0.4
41.3
10.8
2.4
14.2
1.7
112.7
3.6
4.4
4.3
0.9
SE
0.2
6.1
0.4
0.2
0.2
0.2
8.2
1.0
0.2
0.2
0.6
9.5
1.1
0.2
1.0
0.3
7.1
0.6
0.2
0.7
0.5
6.0
0.8
0.2
0.9
0.3
8.3
0.7
0.2
0.2
0.3
TEMPERATE DESERT
TEMPERATE STEPPE
TROPICAL/SUBTROPICAL
DESERT
TROPICAL/SUBTROPICAL
STEPPE
WARM CONTINENTAL
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
124.5
147.9
42.0
86.0
94.2
222.4
38.8
66.5
32.4
236.1
112.6
141.7
30.8
68.0
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
112.5
13.8
1.6
4.6
3.0
90.5
5.2
1.4
6.2
4.4
86.8
9.0
2.0
6.0
3.3
0.8
0.1
0.3
0.2
5.0
0.3
0.2
1.5
0.2
6.1
0.5
0.2
0.5
97.5
11.2
2.3
5.2
1.5
69.8
4.5
2.1
7.9
1.9
75.5
7.1
2.4
6.6
3.3
0.8
0.1
0.3
0.2
5.1
0.4
0.2
1.5
0.2
6.1
0.5
0.2
0.5
77.1
8.8
3.4
6.3
0.5
48.7
3.7
3.3
12.7
0.6
61.0
5.5
3.3
8.0
3.4
0.8
0.2
0.3
0.3
5.1
0.4
0.2
1.5
0.2
6.1
0.5
0.2
0.5
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
260.1
259.5
195.8
56.1
99.9
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
2.8
40.7
13.1
0.9
14.2
0.1
2.2
0.9
0.1
2.0
0.6
27.0
8.1
1.3
19.5
0.1
2.2
0.9
0.1
2.0
0.0
16.0
5.2
2.0
31.5
0.1
2.2
0.9
0.1
2.0
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
# Extreme Events
Event #
Event Size
Extreme CDD
CDD
224.0
214.5
121.2
44.3
81.7
174.9
43.4
89.4
15.9
19.6
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
4.2
87.6
9.2
1.4
6.7
5.1
119.0
9.7
2.3
3.8
0.2
9.4
0.7
0.2
1.1
0.2
3.7
0.6
0.2
0.1
1.5
71.1
6.9
2.1
8.4
2.7
111.2
7.7
2.8
4.0
0.2
9.4
0.7
0.2
1.1
0.2
3.8
0.6
0.2
0.1
0.4
51.3
5.2
3.0
11.8
1.2
95.5
6.2
3.6
4.4
0.2
9.4
0.7
0.2
1.1
0.2
3.8
0.6
0.2
0.1
50
51
52
53
54
55
56
57
58
59
5
60
Table S3. Summary of results of simple linear regressions relating annual precipitation vs. year
61
for each of the 144 sites with precipitation datasets spanning 100 years (12 from each of the 12
62
ecoregion divisions). Shown are the number of sites with no statistically significant temporal
63
trends in annual precipitation (69% overall), the number of sites with significant relationships
64
(most have very low r2 values), the number of sites with significant relationships and r2 values
65
>0.10, and the number of sites with negative relationships (4% overall).
66
Ecoregion (12 sites in each)
HOT CONTINENTAL
MARINE
MEDITERRANEAN
PRAIRIE
SAVANNA
SUBARCTIC
SUBTROPICAL
TEMPERATE DESERT
TEMPERATE STEPPE
TROPICAL/SUBTROPICAL DESERT
TROPICAL/SUBTROPICAL STEPPE
WARM CONTINENTAL
ALL COMBINED (144 total)
No temporal
relationship
10
6
8
9
11
4
10
7
9
10
8
7
99 (69%)
67
68
69
70
71
72
73
6
Significant
relationships
(p<0.05)
2
6
4
3
1
8
2
5
3
2
4
5
45 (31%)
Significant
relationships (p<0.05
and r2 > 0.10)
0
1
0
0
0
6
0
3
1
0
0
3
14 (9.7%)
Negative
slopes
(p<0.05)
0
0
1
1
1
0
0
0
2
1
0
0
6 (4.2%)
40
Extreme Wet Years
Extreme Dry Years
Frequency
2
r = 0.195
p < 0.001
30
20
10
0
1900
1920
1940
1960
1980
2000
1920
1940
1960
1980
2000
Decade
74
Dry Years
250
Wet Years
Frequency
2
r = 0.549
p = 0.014
200
150
100
50
0
1900
75
76
77
78
79
80
81
82
83
84
1920
1940
1960
1980
2000
1900
1920
1940
1960
1980
2000
Decade
Figure S2. Top: Temporal trends in the occurrence of extreme wet and dry years by decade for
the 12 ecoregions (each point is the sum of the number of statistically defined extreme years that
occurred in each decade for 12 sites representing each ecoregion). Bottom: Mean values for all
12 ecoregions (144 sites). At the ecoregion level, there were no significant trends in dry years,
but 5 ecoregions showed statistically significant trends for the frequency of extreme wet years
increasing in more recent decades. These were: Marine: p=0.01; r2=0.58; slope = 0.17;
Mediterranean : p=0.05, r2=0.39; slope=0.12; Subarctic: p=0.001; r2=0.75; slope = 0.15;
Temperate Desert: p=0.02; r2=0.49; slope=0.2: Warm Continental: p=0.04; r2=0.42; slope =0.12.
7