Auxiliary Materials
TREE-RING-BASED SEVEN CENTURY DROUGHT RECORDS FOR THE
WESTERN HIMALAYA, INDIA
Ram R Yadav
Birbal Sahni Institute of Palaeobotany
53, University Road
Lucknow 226007, India
Phone: 091-522-2742907
Mobile: 09450394957
Fax: 091-522-2740485
Email: rryadav2000@gmail.com
1. Data and Methods
1.1 Tree-Ring Data
[1]
The increment core samples from Himalayan cedar (Cedrus deodara (Roxb.) G. Don) and
neoz pine (Pinus gerardiana Wall ex. Lamb) were collected from nine and two moisture stressed
sites respectively in Kinnaur, a cold arid region in Himachal Pradesh, the western Himalaya. The
tree core samples collected in summer 2005, 2006 and 2011 from ecologically homogeneous sites
were used together to develop large chronology network for this area. Undisturbed trees of
different age classes without any visible sign of lopping or fire were selected for sampling
using an increment borer. The increment core samples were air dried and fixed on wooden
support using glue so that the cross surfaces face atop. The cross surface of the mounted
increment core samples were polished with different grades of abrasives to make the cellular
details of growth rings discernible under the binocular microscope. The ring width sequences
among samples were precisely dated to the exact calendar year by using pattern matching
within a tree and between trees from a site and different sites using skeleton plotting [Stokes
and Smiley, 1968]. The ring widths in dated samples were measured using the LINTAB
measuring system with a resolution of ±0.01 mm. The dating of growth ring sequences were
crosschecked using COFECHA, a dating quality check program [Holmes, 1983] and ring
width plots [Rinn, 1991]. The tree-ring width chronologies of Himalayan cedar (nine sites)
1
and neoza pine (two sites) were developed using the program ARSTAN [Cook, 1985]. For
detrending of measurement series conservative method of cubic smoothing spline with a 50%
frequency response cut off width equal to 2/3rd of the individual series length was employed.
However, before detrending, an adaptive power transformation was applied to stabilize the
variance in heteroscedastic tree-ring width measurement series [Cook and Peters, 1997]. The
growth trends were removed from the power transformed individual measurement series by
subtraction, which minimizes the end fitting-type bias as compared to the ratios. All
detrended series of respective sites were averaged to a mean chronology by computing the
biweight robust mean in order to reduce the influence of outliers. The population signal in the
mean chronology gradually weakens in early part of the chronology due to decline in sample
replication. The expressed population signal (EPS) of 0.85, considered to be a reasonable
threshold for acceptance of chronology quality [Wigley et al., 1984] in dendroclimatic
studies, was taken into account to truncate the chronologies for further studies. The site and
species chronology statistics and chronology plots with expressed population signal (eps) are
shown in tale S1 and Figure S1. All the site and species chronologies showed strong common
signal as measured by cross-correlation analysis for the common period AD 1660-2005 (table
S2).
2
Table S1. Site chronology statistics. The details of site locations are shown in figure 1. EPSexpressed population signal, MI-mean index, MS-mean sensitivity, SD-standard deviation,
AR1-first order autocorrelation.
1
Akpa*
31º35´ N-78º 23´E
1355-2010
41/30
Ist Year
with EPS
>0.85
1435
2
Jangi*
31º36´ N-78º 25´ E
1353-2005
28/18
1535
0.995
0.397
0.404
0.452
3
Katgaon*
31º32´ N-78º 16´ E
1480-2005
81/53
1540
0.987
0.399
0.377
0.341
4
Kilba*
31º31´ N-78º 08´ E
1432-2005
32/22
1515
1.004
0.375
0.371
0.388
5
Nichar*
31º33´ N-77º 58´E
1580-2005
47/32
1640
0.998
0.335
0.328
0.336
6
Purbani*
31º35´ N-78º 18´ E
1257-2005
55/36
1310
0.990
0.395
0.340
0.235
7
Ralli*
31º34´ N-78º 23´ E
1376-2005
51/39
1430
0.982
0.458
0.395
0.225
8
Roghi*
31º32´ N-78º 17´ E
1388-2005
61/45
1440
0.989
0.418
0.378
0.304
9
Sangla*
31º25´ N-78º 16´ E
1607-2005
24/19
1660
1.000
0.362
0.362
0.408
10
Akpa**
31º35´ N-78º 23´ E
1203-2010
91/77
1285
0.992
0.486
0.389
0.113
11
Purbani**
31º35´ N-78º 18´ E
919-2005
35/30
1495
0.980
0.552
0.457
0.231
S.
No.
Site
Location
Chronology
length (A.D.)
Cores/
trees
MI
MS
SD
AR1
0.996
0.400
0.371
0.342
* Himalayan cedar, ** Neoza pine
Figure S1. (a) Standard version of the Himalayan cedar chronologies (1-9) and neoza pine
(10-11), (b) change in eps level over the length of chronologies. The eps values were
calculated over 50-years period with the slide of 25 years. The numbers indicate sites as in
table 1; Himalayan cedar (1-9) and neoza pine (10-11).
3
Table S2: Correlation among the site and species chronologies [1660-2005]; Details of sites
are the same as specified in Table S1.
Sites/
species
2*
3*
4*
5*
6*
7*
8*
1*
2*
3*
4*
5*
6*
7*
8*
9*
10**
.904
.818
.789
.819
.796
.927
.697
.669
.911
.863
.925
.875
.865
.884
.766
.856
.872
.861
.859
.769
.908
.851
.853
.893
.909
.831
.907
.904
.855
.864
.874
.896
.825
.814
.736
.927
.865
.860
.800
9*
.813 .836 .828 .815 .745
10**
.911 .853 .764 .787 .672
11**
.858 .830 .818 .860 .728
* Himalayan cedar, ** Neoza pine
.893
1.2 Climate data
The precipitation data of five weather stations in Satluj valley close to the sampling sites in
Kinnaur, Himachal Pradesh were used in this study (Table S3) for tree-growth/climate
relationship. Strong coherence in precipitation data of these stations as measured by crosscorrelation was indicated (Table S4).
Table S3. Location of meteorological stations and length of records
Station
Length
Kilba
Altitude
(m)
1901-2000 2480
Position
31º 31´ N - 78º 09´ E
Nichar
1930-2001 2322
31º 35´ N - 77º 57´ E
Kalpa
1951-2004 2756
31º 32´ N - 78º 15´ E
Sangla
1951-2001 2674
31º 25´ N - 78º 15´ E
Purbani
1951-2004 2964
31º 35´ N - 78º 21´ E
4
Table S4. Correlation between annual (January-December) precipitation of different stations
used in present study (two tailed p values are given in brackets). The correlations were
calculated for the common period 1951-1995.
Station
Kilba
Nichar
Kalpa
0.553
(0.0001)
Nichar
Sangla
Purbani
0.632
(0.0001)
0.748(0.
0001)
0.801
(0.0001)
0.539
(0.0001)
0.462
(0.0014)
0.422
(0.0039)
0.444
(0.0022)
0.528
(0.0002)
0.767
(0.0001)
kalpa
Sangla
REFERENCES
Cook, E. R. (1985), A time series approach to tree-ring standardization, Ph.D. thesis, Univ. of
Ariz., Tucson, 171 pp.
Cook, E. R., and K. Peters (1997), Calculating unbiased tree-ring indices for the study of
climatic and environmental change, Holocene, 7, 361–370, doi:
10.1177/095968369700700314.
Holmes, R. L. (1983), Computer-assisted quality control in tree-ring dating and measurement,
Tree-Ring Bull., 43, 69–78.
Rinn, F. (1991), TSAP-Win time series analysis and presentation for dendrochronology and
related applications, version 0.53 for Microsoft Windows, Rinn Tech, Heidelberg,
Germany, 91 pp.
Stokes, M. A., and T. L. Smiley, (1968), An Introduction to Tree-Ring Dating, The
University of Chicago Press, Chicago, 73 pp.
Wigley, T. M. L., K. R. Briffa, and P. D. Jones (1984), On the average value of correlated
time series with applications in dendroclimatology and hydrometeorology, Int. J.
Climatol., 8, 33–54.
5