Tree-ring analysis of kauri (Agathis australis)

New Zealand Tree-Ring Site Reports
Tree-ring analysis of kauri (Agathis australis) timbers from
a colonial-era villa in Birkenhead, North Shore City
Jan Wunder, Gretel Boswijk & Peter Crossley
NZTRSR 31
2009
School of Environment1
Working Paper 38
(ISSN: 1179-4585 ISBN: 978-0-9582805-5-6)
The University of Auckland
Tree-Ring Laboratory,
School of Environment,
The University of Auckland, Private Bag 92019, Auckland, New Zealand
1
formerly School of Geography, Geology and Environmental Science (ISSN: 1178-4563)
New Zealand Tree-Ring Site Report 31
Tree-ring analysis of kauri (Agathis australis) timbers from a
colonial-era villa in Birkenhead, North Shore City
This is a technical archive report describing recent dendrochronological analysis of kauri timbers from a
colonial-era villa in Birkenhead district, North Shore City. The report describes the calendar dating of kauri
timbers from a veranda of the villa and considers aspects of chronology building using low sample sizes.
It should be noted that although the tree-ring dates will not change, interpretation based on these dates
may change as new information comes to light.
Summary
Tree rings are an important archive of past climate phenomena such as the El Niño-Southern Oscillation
(ENSO). The ENSO reconstruction based on tree rings of kauri (Agathis australis) is currently being extended from the last ca. 400 years to the last Millennium. In this study, we used tree-ring information from
kauri timbers of a colonial-era villa built in the 1870s or 1880s in Birkenhead, North Shore City, to improve
the quality of the current master chronology by increasing its sample depth (tree-ring information per calendar year) during the data scarce time window of AD 1000 – AD 1500. Analysis of 149 samples from
these kauri timbers resulted in a 249-year site chronology spanning from AD 1063 to AD 1311 (BIRKa)
and a 116-year five-timber sequence spanning from AD 1360 to AD 1475 (BIRKb). Many samples were
characterised by very narrow rings, many resin bands and wedging rings suggesting that they originated
from old trees (800+ years) with long periods of suppressed growth. Both, the site chronology and the
five-timber sequence, are important contributions to a 1000 year-high quality master chronology of kauri
since they will significantly increase the sample depth during the first half of the last Millennium.
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New Zealand Tree-Ring Site Report 31
Tree-ring analysis of kauri (Agathis australis) timbers from a
colonial-era villa in Birkenhead, North Shore City
Introduction
Tree-ring based reconstructions of climate phenomena such as the El Niño-Southern Oscillation (ENSO)
require master chronologies with high sample depth, i.e. tree-ring information per calendar year. High
sample depth increases the likelihood of capturing a common signal in the analysed tree-ring sequences,
and well replicated chronologies assure an accurate crossdating process. However, current ENSO reconstructions using tree rings of kauri (Agathis australis) are limited to the last 400 to 500 years (e.g. Fowler
2008) since the sample depth of the existing long-term kauri chronology (1724 BC – AD 2002, Boswijk et
al. 2006) is relatively low prior to AD 1500. Recent attempts to increase the sample depth of the kauri
master chronology focus on analysing archaeological timbers and subfossil kauri since most old living
kauri trees are strictly protected and the Department of Conservation permits coring only in very rare
cases. In this study, we analysed kauri timber from the veranda of a colonial-era villa (Fig. 1) in Birkenhead, North Shore City, to increase the sample depth of the master chronology from AD 1000 to AD 1500
in order to achieve a high-quality millennial length chronology suitable for climate reconstructions.
Fig. 1: The veranda of the analysed kauri villa (Birkenhead Villa), 16 Maritime Terrace, North Shore City. The veranda boarding was replaced in February 2007 and the old kauri timber analysed in this study, Photo: J. Wunder,
Nov. 2008.
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New Zealand Tree-Ring Site Report 31
Material & Methods
Birkenhead Villa
The kauri villa, referred to here as “Birkenhead Villa”, is situated at 16 Maritime Terrace, Birkenhead District, North Shore City (36°49’04’’ S, 174°44’06’’ E). The city belongs to the Auckland region and is located north of the Waitemata Harbour and Auckland City (Fig. 2).
The first houses of European settlers in the region of North Shore City were built in the 1840s (McClure
th
1987), and today the city’s 223,000 inhabitants make it the 4 largest city in New Zealand (Statistics New
Zealand 2008). Most of the villas in the early years were built using timber from kauri. Tree-ring dating of
timbers from other buildings constructed in the 1870s to 1900s indicates that trees > 500 years old (e.g.,
Lorrey et al. 2004, Boswijk 2007) were being felled to supply the timber industry.
The exact construction date of the villa is unknown, however, it is estimated that the villa was built either
in the 1870s or 1880s; a small extension to the sitting room was made in the 1920s, and a section of a
1
porch was enclosed to make a laundry in the mid 1970s (Leonard Bell , personal communication). The
veranda was modified over time, in the 1920s some of it was enclosed to make a gallery space, which
was reversed in the mid 1970s. Furthermore, a few boards were replaced at various times in the 1970s
and 1980s, and the original wooden steps were replaced with concrete steps. In February 2007, the veranda timber was replaced, providing an opportunity to sample the old boarding for tree-ring analysis.
North Shore City
16 Maritime Terrace,
Birkenhead
North Shore City
Birkenhead
North Shore City,
Birkenhead
Auckland City
Fig. 2: Location of the analysed kauri villa (Birkenhead Villa) at 16 Maritime Terrace, North Shore City (left), the
Waitemata Harbour (bottom right) and the relative position of North Shore City with New Zealand (top right), Satellite
photos: Google Earth 2009, Blank map of New Zealand: geography.about.com.
1
Associate Professor at the Department of Art History, University of Auckland and owner of Birkenhead Villa.
3
New Zealand Tree-Ring Site Report 31
Sampling
Cross sections of the veranda boards were taken using a chainsaw. The resulting 169 pieces of timber
were macroscopically identified: 149 were derived from kauri (Agathis australis, Table A1 and A2), 18
from another endemic conifer species, possibly Totara (Podocarpus totara, Table A3) and two pieces
from (exotic) Monterey Pine (Pinus radiata, Table A3). In this report, we focus on kauri timber. Out of the
149 kauri samples, 130 were derived from large boards (cross section of ca. 138 x 20 mm), the remaining
19 from smaller boards (ca. 105 x 25 mm, Fig. 3). For nearly all kauri samples, the type of board was
classified as tongue & groove (145); the remaining four samples were from boards with two grooves on
each side (referred to as groove & groove boards).
Sample preparation & pre-screening
The site was assigned a four letter code, BIRK, and the samples were labelled with a unique three-letter
three-number code (e.g. BIR001). After collection, the cross-sectional surface of each sample was
sanded to a fine polish using increasingly fine grades of sand paper (up to grit 1200). The clarity of the
ring pattern was noted as well as special or unusual features (e.g. resin bands). From the 149 kauri samples, 75 (ca. 50%) were assumed to be suitable for tree-ring analysis, i.e. they contained at least ca. 40 to
50 consecutive rings. Shorter sequences are assumed to be too short to contain a unique growth pattern
and may lead to spurious results during crossdating (Cook & Kairiukstis 1990, English Heritage 2004).
Measurement & crossdating
The width of the annual rings was measured using a binocular microscope and a travelling stage fitted
with a linear encoder which is connected to a computer (Fig. 3). Ring width data were recorded using an
input program (Input for 32-bit Windows, Tyers 2004). Once a set of suitable series had been measured,
the series were compared to each other to identify those that crossmatched. Crossmatched series were
then averaged together to construct a working site chronology. Averaging the ring width series can reduce the ‘noise’ of endogenous effects on tree-ring formation (e.g. tree competition) and enhance the exogenous climate effect on ring formation on which crossdating is dependent (Baillie 1982). The working
site chronology was then compared to master and independent site chronologies / dated sequences
(modern sites, archaeological sites, subfossil sites) to identify a calendar date for the chronology. Further
samples from the Birkenhead Villa assemblage were measured and crossdated to the working site chronology, which was incrementally updated to include all newly dated series.
Fig. 3: Binocular microscope and travelling stage (left) used to analyse timber of Birkenhead Villa (right), the crosssections are ca. 138 x 20 mm (large pieces) and ca. 105 x 25 mm (small pieces, e.g. top left), Photos: J. Wunder,
Sep. 2008 and Feb. 2009.
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New Zealand Tree-Ring Site Report 31
Statistical crossdating was performed using the crossdating programs CROS73 (Baillie & Pilcher 1973)
and Cross84 (Munro 1984) included in the Dendro for Windows suite (version 1.32.10.4, Tyers 2004).
These programs compare pairs of tree-ring series and calculate the correlation coefficient (r) for every
position of overlap of the previously standardised series. A Student’s t-statistic is calculated to provide a
measure of the probability of the r-value arising by chance (Baillie 1982). Earlier work on kauri adopted a
criterion of identifying t-values > 6.00 as highly significant, provided that the visual match is acceptable
(Boswijk et al. 2000).
The crossdating results suggested by Dendro for Windows were verified using the tree-ring crossdating
program COFECHA (Holmes 1983, Grissino-Mayer 2001). For each detrended tree-ring series,
COFECHA creates a master chronology from every other series, and then calculates the correlation coefficient between every 50-year segment of that series and the master chronology (NOAA Paleoclimatology
Program 2005). The resulting correlation matrix can be used to examine flagged (problem) segments,
changes in sample depth over time, and changes in average correlation over time (NOAA Paleoclimatology Program 2005). If not stated differently, all crossdating statistics (t- and r-values) in this report are
based on Cross84 (Munro 1984).
All matches suggested by the crossdating programs were checked visually using line plots, overlaid on a
light box. Occasionally very high t-values may be obtained between series. If supported by close visual
agreement of ring-width plots and macroscopic features of the wood samples (e.g. colour), this may indicate that these samples were obtained from the same original length of timber or were cut from the same
tree. In this case, such “same-tree” series were averaged to form a timber-sequence which was subsequently used for chronology building. This procedure reduces the weight of assumed “same-tree”-material
during the chronology building (English Heritage 2004).
False and missing rings
Generally, a key issue during the chronology building process is the secure identification of false rings.
False rings can occur when the growing season is interrupted by a period of inferior growth (e.g. during a
drought period in spring). During this period the stressed tree may form new tissue with thick cell walls
that look similar to latewood cells, and the so formed ‘ring boundary’ looks similar to the boundary of a
real ring. False rings can usually be identified by a slow decrease of cell wall thickness between false
‘latewood’ cells and later formed earlywood cells, whereas real ring boundaries are usually characterised
by a sharp border between latewood and earlywood (Stokes & Smiley 1968). Missing or locally absent
rings are a more extreme expression of stress, they indicate years in which none or only a partial ring was
formed.
For kauri, the formation of false and missing rings is characteristic for many sites (e.g., Boswijk et al.
2006). Crossdating within and between trees of one particular site and against other chronologies usually
helps to resolve problems with individual series. If not resolvable, these series are discarded from further
analysis.
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New Zealand Tree-Ring Site Report 31
Results
The assemblage collected from Birkenhead Villa comprised 149 kauri samples, 75 of those had more
than ca. 40 to 50 rings that are assumed to be required for the crossdating process (Cook & Kairiukstis
1990, English Heritage 2004). Crossdating within the individual tree-ring series of the assemblage resulted in twelve groups that are referred to as timber sequences BIRS1 to BIRS12. Each timber sequence
consists of two to five tree-ring series (Table A1, Appendix). The high mean t-values for each sequence
(up to t = 49.09, Table A1) and similar macroscopic appearance of the timber (colour, resin bands, etc.)
suggest that the series within each sequence are “same-tree”-material.
Of the twelve timber sequences, three were calendar dated by comparison to master chronologies
1
(AGAUl07r and AGAUc07r , TRL unpubl.): BIRS1 (four series: BIR035, BIR38, BIR045, BIR088) & BIRS2
(two series: BIR153, BIR166) are the basis of the small site chronology BIRKa (AD 1063 – AD 1311) and
BIRS3 (five series: BIR033, BIR052, BIR057, BIR137, BIR138) represents a five-timber sequence labelled BIRKb (AD 1360 – AD 1475, Fig. 4). Thus, the three sequences are based on 11 series (all tongue
& groove large) whose length ranged from 65 to 213 rings, with an average length of 117 rings.
AD 1063
AD 1475
BIR153
BIR 166
BIR 045
BIR 035
BIRKa
BIR 088
BIR 038
BIRKb
BIR 138
BIR 052
BIR 033
BIR137
BIR 057
Fig. 4: Composition of the site chronology BIRKa (BIRS1: horizontal hatching, BIRS2: vertical hatching) and fivetimber sequence BIRKb (BIRS3: white). Each bar represents one series, with all bars arranged by location and
aligned by end date.
Site chronology BIRKa
The site chronology, BIRKa, spans 249 years from AD 1063 to AD 1311 (Fig. 4). BIRKa was built using
two dated timber sequences: the four-timber sequence BIRS1 (BIR035, BIR038, BIR045, BIR088) and
the two-timber sequence BIRS2 (BIR153, BIR166, see Table 1, Table A4, Table A6).
For BIRS1, the (very) high t-values between the series BIR035, BIR038 and BIR088 and similar colour
and structure of these timbers strongly suggests that the three series are “same-tree”-material. The
crossdating statistics favour a similar classification of the remaining series BIR045 (Table 1), even though
its colour and structure deviates slightly from the other series. This variation indicates that BIR045 either
originated from a different part of the trunk of the same tree or a different tree with very similar growth
patterns. The two series of BIRS2 could be also “same-tree” material, even though the t-values are con1
AGAUl07r is comprised of raw modern and archaeological data and spans AD 911 – AD 2002.
AGAUc07r is comprised of raw modern, archaeological and subfossil data and spans 1724 BC – AD 2002.
6
New Zealand Tree-Ring Site Report 31
siderably lower as within BIRS1. Therefore, the site chronology BIRKa may consist of two to three trees
only.
Table 1: Triangular t-value matrix of cross-dating values for all individual series in the chronology BIRKa.
Symbols: - = t-values less than 3.00, * = empty triangle. Average series length: 146 rings (max: 213, min: 65).
Filenames
start
BIR035
AD1063
BIR038
AD1099
BIR045
AD1073
BIR088
AD1129
BIR153
AD1163
BIR166
AD1167
end
AD1264
AD1311
AD1251
AD1279
AD1227
AD1231
BIR035
AD1063
BIR038
AD1099
BIR045
AD1073
BIR088
AD1129
BIR153
AD1163
BIR166
AD1167
AD1264
AD1311
AD1251
AD1279
AD1227
AD1231
*
*
*
*
*
*
30.53
*
*
*
*
*
21.13
17.12
*
*
*
*
35.50
23.39
21.17
*
*
*
3.22
3.40
*
*
4.82
4.57
3.04
3.77
9.50
*
n = 15, min t = 1.88, max t = 35.50, mean t = 12.39, s.d. = 11.00.
The signal strength of the site chronology BIRKa is consistently very high across different time windows
(Table 2): for all nine time windows, the average segment correlation never falls below 0.80 (Table 2).
Table 2: Quality control and dating check of tree-ring measurements of BIRKa (COFECHA): correlation of series by
segments (for more details see section Material & Methods, p.5).
Series
BIR035
BIR038
BIR045
BIR088
BIR153
BIR166
Time span (all AD)
AD1063 AD1264
AD1099 AD1311
AD1073 AD1251
AD1129 AD1279
AD1163 AD1227
AD1167 AD1231
Av. segment correlation
1050
1099
0.94
1075
1124
0.94
0.84
0.92
0.92
0.93
0.9
1100
1149
0.94
0.83
0.92
0.9
1125
1174
0.90
0.85
0.88
0.86
1150
1199
0.86
0.90
0.78
0.87
0.72
0.70
1175
1224
0.91
0.89
0.86
0.87
0.74
0.76
1200
1249
0.91
0.91
0.90
0.88
0.73
0.75
1225
1274
0.90
0.86
0.89
0.87
1250
1299
0.87
0.80
0.84
0.85
0.88
0.82
0.82
0.83
Five-timber sequence BIRKb
The five-timber sequence BIRKb, spans 116 years from AD 1360 to AD 1475 (Fig. 3). BIRKb represents
the dated five-timber sequence BIRS3 (BIR033, BIR052, BIR057, BIR137, BIR138). High t-values of the
crossdating table (Table 3) and similar colour and structure of the timber suggest that the five series were
derived from the same tree. The signal strength of the five-timber sequence BIRKb is also consistently
very high across different time windows (Table 4, Table A5, Table A7).
Table 3: Triangular t-value matrix of cross-dating values for all individual samples in the five-timber sequence BIRKb.
Symbols: * = empty triangle. Average series length: 88 rings (max: 95, min: 79).
Filenames
start
BIR033
AD1382
BIR052
AD1361
BIR057
AD1397
BIR137
AD1393
BIR138
AD1360
end
AD1469
AD1454
AD1475
AD1474
AD1454
BIR033
AD1382
AD1469
BIR052
AD1361
AD1454
BIR057
AD1397
AD1475
BIR137
AD1393
AD1474
BIR138
AD1360
AD1451
*
*
*
*
*
12.13
*
*
*
*
12.14
8.95
*
*
*
11.21
10.90
14.56
*
*
14.18
22.51
8.20
9.00
*
n = 10, min t = 8.20, max t = 22.51, mean t = 12.38, s.d. = 3.94.
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New Zealand Tree-Ring Site Report 31
Table 4: Quality control and dating check of tree-ring measurements of BIRKb (COFECHA): correlation of series by
segments (for more details see section Material & Methods, p.5).
Series
BIR033
BIR052
BIR057
BIR137
BIR138
Time span (all AD)
AD1382
AD1469
AD1361
AD1454
AD1397
AD1475
AD1393
AD1474
AD1360
AD1454
Av. segment correlation
1350
1399
0.92
1375
1424
0.92
0.92
0.86
0.81
0.89
1400
1449
0.87
0.76
0.86
0.80
0.83
1425
1475
0.76
0.70
0.80
0.73
0.78
0.95
0.88
0.83
0.75
0.97
Comparison with other chronologies and dated sequences
A comparison of the site chronology BIRKa and the five-timber sequence BIRKb against independent
master and site chronologies and dated sequences revealed very good crossdating results with the master chronologies, i.e. the modern & archaeological sites chronology and the long chronology (modern +
archaeological + subfossil sites, see Table 5). The crossdating results against the independent site chronologies and dated sequences have to be treated carefully since BIRKa & BIRKb as well as most site
chronologies are characterised by a (very) low sample depth during the overlap period. For example, a
comparison of BIRKb (one tree) against Yakas1 (one tree) is a comparison of two individual trees from
different sites, for which low t-values could occur. Nevertheless, BIRKa and BIRKb crossdate well with
most house site chronologies and the Display piece, a logging relic of unknown origin. However, the
crossdating with material from the two subfossil sites (Hoa001 and Yakas1) resulted in considerably lower
t-values (Table 5).
Note that the term “site chronology” is used for both chronologies of modern (ecological) sites and archaeological sites: Modern site chronologies are characterised by a common signal derived from increment cores taken at one forest site, i.e. the tree-ring formation of different trees at that site occurs under
similar abiotic conditions (soil, climate, etc.). For archaeological site chronologies, the term “site chronology” refers to a set of all timbers used to build a house or a wooden structure, irrespective of the origin
of the kauri trees that were used during the building process. Hence, the common signal of archaeological
site chronologies may be based on trees that originate from different forest sites characterised by a different set of abiotic factors that influenced the formation of the tree rings.
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New Zealand Tree-Ring Site Report 31
Table 5: Comparison of BIRKa and BIRKb to the current (working) kauri master chronologies (AGAUl07r = master
modern sites + archaeological sites, AGAUc07r = master long chronology = modern sites + archaeological sites +
subfossil sites), to archaeological site chronologies (Wynd28a = Wynyard 28a, SPchurch = St. Paul’s church,
George1 = Georgina 1), to logging relics (Dsp001 = Display piece), to modern site chronologies (Manaia and Mt.
Moehau) and to subfossil timber sequences (Hoa001 = Hoanga 001 and Yakkas 001). ‘Date span’ refers to the start
and end dates of each chronology or sequence. ‘Overlap’ refers to the length of the common period between the
reference chronologies / dated sequences and BIRKa / BIRKb.
Type of chronology / dated
sequence (region)
Date span chronology/
dated sequence
Filename
start
dates
(Reference)
end
dates
AD
Overlap
(years)
BIRKa
1063- AD 1311
t-value
AD
r
BIRKb
1360- AD1475
Overlap
(years)
t-value
r
Master chronology
AGAUl07r
AD911
AD2002
249
11.56
0.63
116
6.56
0.55
1724BC
AD2002
249
10.65
0.59
116
6.65
0.55
AD940
AD1383
249
9.87
0.56
24
-
-
AD1125
AD1861
187
7.55
0.51
116
5.62
0.48
AD1207
AD1872
105
3.44
0.33
116
3.02
0.28
AD911
AD1600
249
7.62
0.45
116
5.44
0.47
AD1269
AD1998
43
-
-
116
4.92
0.43
AD1360
AD1980
0
-
-
116
-
-
(Boswijk
AD1093
AD1660
219
3.98
0.26
2004)
Yakas1
(Boswijk &
AD304
AD1273
211
4.73
0.32
Palmer
2004)
Note: no crossdating statistic was calculated for overlaps < 50 years (years in italics).
116
5.05
0.44
0
-
-
AGAUc07r
(TRL
unpubl.)
(TRL
unpubl.)
Archaeological sites
(Auckland, Northland)
Wynd28a
(Lorrey et al.
2004)
SPchurch
(Boswijk
2007)
George1
(Bridge
unpubl.)
Logging relic
(origin unknown)
Dsp001
(TRL
unpubl.)
Modern sites (Coromandel)
Manaia
Mt. Moehau
(Boswijk et
al. 2000)
(TRL
unpubl.)
Subfossil sites (Northland)
Hoa001
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New Zealand Tree-Ring Site Report 31
Undated material
The remaining nine timber sequences (BIRS4 to BIRS12) could not be dated against master chronologies
(AGAUl07r and AGAUc07r, TRL unpubl., Table A1). Most of this material is characterised by very narrow
rings and many resin bands. Hence it seems plausible that some of the material originates from old trees
(800+ years) that experienced very long periods of suppressed growth (Fig. 5), which may have affected
their cross-dating potential.
The rest of the 38 measured series remain undated (Table A1, Appendix) since they do not crossdate to
any of the sequences from the site (BIRS1 to BIRS12) or to any master chronologies. Again, the main
reasons for this are probably suppressed growth patterns with many very narrow, wedging and locally
absent tree rings and areas with resin filled cells that affected both the crossdating potential and also the
clarity of the ring boundaries (Fig. 5). For the short series (ca. 50 rings) without suppressed growth pattern, the overlap to potentially crossdating series within the Birkenhead assemblage may be not long
enough to calculate reliable crossdating statistics.
Resin bands
Ray
20 mm
Ring boundaries
Fig. 5: Left image: Examples of resin bands and narrow wedging rings (undated series BIR155, BIR043, BIR164
from top to bottom). Right image: Resin bands of BIR067 (not dated). These bands and the suppressed growth pattern with narrow wedging rings were typical features of the measured Birkenhead samples, Photos: J. Wunder, Feb.
2009, right image: Olympus U-TV0.5XC-3 colour view imaging system, magnification 5x.
False rings
The Birkenhead samples contained some false rings. Their clear identification was sometimes difficult
due to very narrow bands of ‘latewood’ cells (only two to three cells wide), i.e. not enough to observe the
above mentioned transition zone between false ‘latewood’ cells and later formed earlywood cells (Stokes
& Smiley 1968). One of the samples, (BIR038, Fig. 6) of the BIRKa chronology, contained such a ‘ring’
that was treated as false ring formed in AD 1201, mainly due to the fact, that none of the other BIRKa
samples contained signs of wedging rings in that particular calendar year.
AD 1201
AD 1200
10
AD 1201
New Zealand Tree-Ring Site Report 31
AD1201
AD1200
Fig. 6: Assumed false ring formed during AD 1201 (BIR038), Photo: J. Wunder, Feb. 2009, Olympus U-TV0.5XC-3
colour view imaging system, magnification 5x.
A verification of this false ring with other series of the kauri master chronology at around AD 1200 is difficult since the master consists of only five to six trees at this time period, depending on the treatment of
“same-tree” material. A comparison of the AD 1201 ring across all samples that contribute to the master
chronology, i.e. series from the sites Wynyard Street and St. Paul’s Church (archaeological timbers),
Hoanga 1 (subfossil sample) and the Display piece (logging relic of unknown origin) revealed that ring-like
structures were formed at two samples from St. Paul’s Church (SPC 141 & SPC 142) immediately after
the establishment of the AD 1200-tree ring (Fig. 7). These had been treated as false rings during the development of the St. Paul’s Church site chronology.
AD1201
AD1201
AD1200
AD1201
AD1200
AD1200
Fig. 7: Ring-like structures formed after AD 1200 at STP141 (left and middle: assumed wedging ring between AD
1200 and AD 1201) and STP 142 (right: assumed false ring during AD 1201), Photos: J. Wunder, Feb. 2009, Olympus U-TV0.5XC-3 colour view imaging system, magnification 5x.
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New Zealand Tree-Ring Site Report 31
Discussion
From the Birkenhead Villa material, a site chronology BIRKa (BIRS1 + BIRS2: AD 1063 – AD 1311) and a
five-timber-sequence BIRKb (BIRS3: AD 1360 – AD 1475) could be developed. Both fall into a time period where replication of tree-ring information is highly desired since the sample depth of the kauri master
chronology between AD 1000 and AD 1500 is particularly low (Fig. 8). This time window falls into the
overlap phase between modern/archaeological material and subfossil material of kauri, i.e. a time period
where the sample depth of subfossil timbers is thinning out and the oldest modern and archaeological
timbers become available (Boswijk et al. 2006). Therefore, the eleven dated series from BIRS1 (one –
two trees), BIRS2 (one tree) and BIRS3 (one tree) will considerably improve the current kauri master
chronology (e.g. AGAUl07r, TRL unpubl., Fig. 8) – and will contribute to an updated high-quality millennial
master chronology suitable for paleoclimate reconstructions.
Frequency of tree-ring series
Sample depth (AD 911 - AD 2002)
400
AGAUl07r (master chronology)
BIRKa (site chronology)
BIRKb (five-timber mean)
300
200
100
0
911
1100
1300
1500
1700
1900
2002
Time (calendar years)
Frequency of tree-ring series
Sample depth (AD 911 - AD 1500)
60
50
40
30
20
10
0
911
1100
1300
1500
Time (calendar years)
Fig. 8: Sample depth of the individual tree-ring series (≠ trees) for the 1092-year-master chronology AGAUl07r (archaeological + modern sites) and the contribution of the site chronology BIRKa and the five-timber mean BIRKb.
BIRKa consists of 6 tree-ring series (2-3 trees), BIRKb of 5 tree-ring series (1 tree). Graph: R for Windows version
2.9.1, R Development Core Team 2009.
For the site chronology BIRKa, the crossdating results against independent master and site chronologies
are generally very good, with exceptions of the house site chronology Georgina St (George1), and the
subfossil timber series Hoanga1 and Yakkas1. However, the overlap between BIRKa and George1 is
across a period when George1 has only one series and it may be possible that such low t-values occur
when comparing one tree with a site chronology consisting of two to three trees. This could also explain
the low t-values of BIRKa derived for the comparison against the two subfossil sites that both represent
only one individual tree.
12
New Zealand Tree-Ring Site Report 31
For the five-timber sequence BIRKb, all crossdating results were fairly good except for the two sites
George1 and Mt. Moehau. For George1, the inferior crossdating statistic may be again a result of the low
sample depth across the overlap period with BIRKb: across the time window AD 1360 to AD 1475, the
George1 site chronology is a mean of two to four tree-ring sequences. In addition, the relatively short
overlap period (116 years) may lead to low t-values. The weak crossdating results between BIRKb and
Mt. Moehau are in line with previous observations suggesting that Mt. Moehau shows weaker crossdating
results against all other kauri sites (Fowler et al. 2004) which may be caused by the potentially different
growth reactions of kauri growing at their altitudinal limit.
Since the Birkenhead timber did not include any dated tree-ring information from around AD 1900, it was
not possible to identify the construction date of the veranda. However, the calendar dates of some series,
as well as other characteristics such as series length, indicates that some of the timber was derived from
trees that were > 800 years old.
“Same-tree” & “Same-site” material
Probably each of the timber sequences BIRS1 to BIRS12 contains (sometimes exclusively) “same-tree”
material. However, even though high t-values of the crossdating statistic and similar colour and structure
of the cross-sections may support that assumption, the variability of tree-ring series within one individual
tree remains unknown. For example, no statistical analysis of the tree-ring patterns at different trunk
heights of kauri has been undertaken, i.e. possible positions of origin for any particular piece of building
timber. Such knowledge would be highly useful to better classify “same-tree” material in building timber,
and to get a better estimate of the total sample depth of trees in archaeological site - and composite
chronologies (combined archaeological site - and modern site chronology).
For the Birkenhead assemblage, as for many other house sites, it is not possible to decide whether all
dated series originated from trees of the same forest site. One potential criterion indicating “same-site”
material may be similar growth patterns of trees at one particular site characterised by a certain regional
climate. This climate forcing influences the trees of one forest site in a similar way - and hence the intrasite correlation of these trees would be higher as compared to inter-site correlations between different
sites. This difference would be reflected in crossdating statistics, i.e. t- and r-values. However, for such a
test of “same-site” material, a higher sample depth of trees would be needed: the three dated sequences
from Birkenhead Villa are clearly not enough to perform such a test. Furthermore, the dated sequences of
Birkenhead Villa only partly overlap (BIRS1 & BIRS2, with a 49 year gap to BIRS3) – therefore it is not
possible to gain any information concerning whether BIRS1/BIRS2 was derived from the same site as
BIRS3 (see Fig. 4).
Sample size & false vs. missing rings
Small sample sizes can affect the clear identification of false rings – and the building of a site chronology
independent of a master chronology: For example, out of the 6 series of BIRKa, one had an AD 1201-ring
that was divided by an apparent boundary such that it looked like two annual rings (Fig. 6). Further analysis with a microscope did not allow for a clear conclusion, even though it favours the classification as
false ring formed in AD 1201. In this case, assuming an independent chronology without reference to a
master chronology, two assumptions are possible: the narrow ring is real and a locally absent ring has to
be added to the five other samples - or the narrow ring is a false ring. Unfortunately, the sample depth of
the master chronology equals only five to six trees around AD 1200 (depending on the classification of
“same-tree” material) – given this sample depth it cannot be falsified that all these trees have an undis13
New Zealand Tree-Ring Site Report 31
covered locally absent ring in the same year, even though the likelihood for such an event appears to be
relatively low. Nevertheless, such an error would offset the chronology by one year, and given low sample
sizes, the probability for those offsets increases when going back in time, especially with regard to millennial chronologies. The question arises how likely such errors are – given a certain small sample size of
trees. Therefore, the proportion of locally absent rings in the kauri master chronology across different time
windows should be analysed to estimate a minimum number of trees that is necessary to ensure the correct detection of all locally absent rings during the process of chronology building.
Interestingly, multi-proxy summer temperature reconstructions based on tree rings and ice cores show a
negative anomaly in the year AD 1201/1202 for both hemispheres, possibly associated with volcanic activity (Jones et al. 1998, Oppenheimer 2003). Future kauri samples dated to around AD 1200 may show
whether kauri populations more than 800 years ago were showing any reaction to this anomaly, i.e.
whether the tree-ring series at that point of time are characterised by locally absent rings or by false rings.
Conclusion
The analysis of Birkenhead assemblage resulted in the development of a site chronology and a five-timber sequence, both will significantly increase the relatively low sample depth of the current kauri master
chronology before AD 1500. Furthermore, the assemblage is an excellent example of how low sample
depth may influence the process of chronology building and what directions of future research may be
useful to facilitate the building of high-quality chronologies suitable for the reconstruction of climate phenomena such as ENSO.
Acknowledgements
We would like to thank Leonard Bell for the opportunity to use old building timber from his villa in Birkenhead for research purposes, Anthony Fowler for helpful comments on an earlier version of the manuscript
and Shane McCloskey for valuable advice regarding the crossdating program COFECHA. JW acknowledges funding by the Swiss National Science Foundation SNF (post-doctoral fellowship PBEZ2-118902).
Appendix
Table A1: Details of all measured kauri samples obtained from Birkenhead Villa.
Table A2: Details of all unmeasured kauri samples obtained from Birkenhead Villa.
Table A3: Details of all unmeasured non-kauri samples obtained from Birkenhead Villa.
Table A4: Inter-tree comparisons of all trees of the site chronology BIRKa (COFECHA).
Table A5: Inter-tree comparisons of all trees of the five-timber sequence BIRKb (COFECHA).
Table A6: Descriptive statistics for each individual series of the site chronology BIRKa (COFECHA).
Table A7: Descriptive statistics for each individual series of the five-timber sequence BIRKb (COFECHA).
14
New Zealand Tree-Ring Site Report 31
References
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Boswijk, G., Fowler, A., and Ogden, J., (2000): Tree-ring analysis of kauri (Agathis australis) from Manaia Sanctuary, Coromandel
Peninsula, New Zealand Tree-ring Site Report 1. Department of Geography Working Paper 9, University of Auckland, Auckland.
Boswijk, G. & Palmer, J. (2004): Tree-ring analysis of sub-fossil kauri (Agathis australis) from Yakas' Farm, Babylon Coast Road,
near Dargaville, Northland, New Zealand Tree-ring Site Report 13. School of Geography and Environmental Science Working
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Peninsula, New Zealand Tree-ring Site Report 14. School of Geography and Environmental Science Working Paper 24, University of Auckland, Auckland.
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(http://www.english-heritage.org.uk/upload/pdf/Dendrochronology.pdf, March 23, 2009).
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Holocene chronologies. Tree-Ring Research 60(1):15-29.
Fowler, A.M. (2008): ENSO history recorded in Agathis australis (kauri) tree rings. Part B: 423 years of ENSO robustness. International Journal of Climatology 28: 21-35.
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Holmes, R. L. (1983): Computer-assisted quality control in tree-ring dating and measurement. Tree-Ring Bulletin 43: 69-78.
Jones, P.D., Briffa, K.R., Barnett, T.P. & Tett, S.F.B. (1998): High-resolution palaeoclimatic records for the last millennium: interpretation, integration and comparison with General Circulation Model control-run temperatures. The Holocene 8: 455-471.
Lorrey A., Lux. J, Boswijk. G, and Crossley, P. (2004): Dendrochronological analysis of salvaged kauri timber from 26 and 28 Wynyard Street, The University of Auckland. New Zealand Tree-ring Site Report 12. School of Geography and Environmental
Science Working Paper 20, University of Auckland, Auckland.
McClure, M. (1987): The story of Birkenhead. Shoal Bay Press, Christchurch, 223 p.
Munro, M.A.R. (1984): An improved algorithm for crossdating tree-ring series. Tree-Ring Bulletin 44: 17-27.
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Stokes, M.A. & Smiley, T.L. (1968): An Introduction to Tree-Ring Dating. University of Chicago Press, Chicago, 73 p.
Tyers, I. (2004): Dendro for Windows Program Guide 3rd edition. Project Report 500b. ARCUS Dendrochronology Laboratory, University of Sheffield, Sheffield.
15
New Zealand Tree-Ring Site Report 31
Table A1: Details of all measured kauri samples obtained from Birkenhead Villa.
Key: sample = number of sample/sequence, timber type: T & G = tongue & groove board (used for flooring of the
veranda), dim. = dimension of sample cross-section, AGR = average growth rate for the measured series, date span
= calendar years, or relative years if undated, ring orientation (comments column) = oblique, radial, tangential, dist.
pith (comments column) = rough estimate of the distance between the pith and the first measured ring of the series
(using a template of concentric rings - only for dated samples), t = mean t-value for sequence (measured using
Cross84, for short series BIRS9 – BIRS11: CROS73).
Sample
BIRKa
BIRKb
Timber
type
Dim.
(mm)
No. of
rings
AGR
Date span
Comments
BIRS1 = dated four-timber sequence (t = 24.81)
BIR035
T & G -large
138 x 20
202
BIR038
T & G -large
139 x 20
213
BIR045
T & G -large
131 x 20
179
BIR088
T & G -large
138 x 20
151
0.51
0.51
0.58
0.59
AD 1063-AD 1264
AD 1099-AD 1311
AD 1073-AD 1251
AD 1129-AD 1279
oblique, dist. pith > ca. 8 cm
oblique, dist. pith > ca. 8 cm
broken (tongue), oblique, dist. pith > ca. 8 cm
oblique, dist. pith > ca. 8 mm
BIRS2 = dated two-timber sequence (t = 9.50)
BIR153
T & G -large
137 x 20
65
BIR166
T & G -large
138 x 20
65
0.98
0.97
AD 1163-AD 1227
AD 1167-AD 1231
oblique, dist. pith > ca. 8 cm
oblique, dist. pith > ca. 8 cm
BIRS3 = dated five-timber sequence (t = 12.38)
BIR033
T & G -large
140 x 20
88
BIR052
T & G -large
131 x 19
94
BIR057
T & G -large
137 x 19
79
BIR137
T & G -large
137 x 19
82
BIR138
T & G -large
140 x 19
92
0.80
0.86
0.92
0.75
0.87
AD 1382-AD 1469
AD 1361-AD 1454
AD 1397-AD 1475
AD 1393-AD 1474
AD 1360-AD 1451
broken (groove), oblique, dist. pith ca. 8 cm
broken (tongue), oblique, dist. pith ca. 8 cm
broken (groove), oblique, dist. pith ca. 8 cm
oblique, dist. pith ca. 8 cm
oblique, dist. pith ca. 8 cm
BIRS4 = undated two-timber sequence (t = 29.91)
BIR030
T & G -large
136 x 20
177
BIR049
T & G -large
136 x 20
173
0.57
0.57
1-177
5-177
BIRS5 = undated five-timber sequence (t = 11.95)
BIR037
T & G -large
138 x 20
100
BIR087
T & G -large
136 x 20
77
BIR136
T & G -large
138 x 20
100
BIR139
T & G -large
137 x 20
73
BIR148
T & G -large
130 x 20
53+10h
0.82
0.58
0.77
0.57
0.52
1-100
24-100
1-100
28-100
48-100
oblique, many wedging rings
oblique, many wedging rings
oblique
oblique
broken (tongue), oblique, 10 last rings not
measured, probably many missing rings
BIRS6 = undated two-timber sequence (t = 49.09)
BIR031
T & G -large
131 x 19
146
BIR162
T & G -large
133 x 19
157
0.65
0.63
12-157
1-157
broken (tongue), oblique
broken (tongue), oblique
BIRS7 = undated two-timber sequence (t = 33.29)
BIR140
T & G -large
140 x 20
178
BIR167
T & G -large
140 x 20
173
0.77
0.8
3-180
1-173
BIRS8 = undated three-timber sequence (t = 16.98)
BIR001
T & G -large
138 x 21
244
0.47
BIR135
T & G -large
139 x 21
245+8h
0.46
BIR145
T & G -large
121 x 40
156
0.55
3-246
1-245
82-237
broken (groove), oblique
oblique
radial
radial
oblique
oblique, last 8 rings not measureable
oblique, broken (groove), groove side: ca. 2 cm are
missing, fungi (inner part difficult to measure)
BIRS9 = undated three-timber sequence (t = 8.60)
BIR002
T & G -small
106 x 27
45
BIR009
T & G -small
107 x 26
49
BIR015
T & G -small
107 x 25
54
1.24
1.18
0.96
1-45
8-56
9-62
oblique
oblique
oblique
BIRS10 = undated two-timber sequence (t = 7.65)
BIR005
T & G -small
105 x 26
52
BIR007
T & G -small
107 x 25
64
1.74
1.33
1-52
15-78
oblique
oblique
BIRS11 = undated three-timber sequence (t = 8.13)
BIR013
T & G -small
106 x 25
51
1.69
BIR018
T & G -small
105 x 26
46
1.85
BIR019
T & G -small
105 x 25
50
1.65
2-52
14-59
1-50
oblique
oblique
oblique
BIRS12 = undated four-timber sequence (t = 13.51)
BIR023
T & G -large
140 x 20
190
BIR029
T & G -large
140 x 19
293
BIR047
T & G -large
139 x 19
290
BIR157
T & G -large
139 x 21
303
16
0.48
0.47
0.46
0.45
51-240
4-296
6-295
1-303
radial
broken (groove), radial
radial
radial, blue coloured rings 213 & 215
New Zealand Tree-Ring Site Report 31
Table A1 continued.
Sample
Timber type
Dim.
(mm)
No. of
rings
AGR
Date
span
Undated series (measured)
BIR003
T & G -small
105 x 26
BIR017
T & G -small
104 x 24
BIR021
T & G -large
139 x 20
BIR024
T & G -large
139 x 20
BIR026
T & G -large
137 x 20
BIR027
T & G -large
139 x 21
BIR028
T & G -large
139 x 21
49
47
46
90
42
43
243
1.53
1.32
2.57
0.87
2.22
1.18
0.51
1-49
1-47
1-46
1-90
1-42
1-43
1-243
BIR032
BIR034
BIR036
BIR042
BIR043
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
138 x 19
137 x 21
139 x 20
138 x 21
131 x 21
249
44
221
46
180
0.52
1.25
0.57
1.76
0.33
1-249
1-44
1-221
1-46
1-180
BIR050
BIR053
BIR054
BIR062
BIR064
BIR067
BIR141
BIR142
BIR143
BIR144
BIR146
BIR147
BIR149
BIR150
BIR151
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
135 x 20
140 x 21
135 x 21
138 x 21
138 x 20
138 x 20
135 x 20
139 x 20
137 x 21
139 x 21
140 x 19
135 x 20
134 x 21
141 x 21
139 x 19
229
189
57
44
46
202
50
198+60h
197
85
114
207
229
98
249
0.38
0.43
0.81
1.27
2.91
0.57
1.17
0.5
0.36
0.7
0.97
0.45
0.5
1.36
0.52
1-229
1-189
1-57
1-44
1-46
1-202
1-50
1-198
1-197
1-85
1-114
1-207
1-229
1-98
1-249
BIR152
BIR154
BIR155
BIR156
BIR158
BIR159
BIR160
BIR161
BIR163
BIR164
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
T & G -large
129 x 20
134 x 19
137 x 20
140 x 20
136 x 21
140 x 21
140 x 20
136 x 20
135 x 20
138 x 20
142
43
172
242
52
231
210
95
182
75+105h
0.57
0.77
0.38
0.55
0.66
0.47
0.54
0.75
0.67
0.47
1-142
1-43
1-172
1-242
1-52
1-231
1-210
1-95
1-182
1-75
BIR165
T & G -large
138 x 21
150+68h
0.51
1-150
Comments
oblique
broken (groove), oblique
oblique
oblique
broken (tongue), oblique
tangential
broken (groove), oblique, very narrow, many wedging
rings, abrupt growth changes
broken (tongue & groove), oblique
oblique
radial
broken (groove), oblique
broken (tongue), oblique, many wedging rings, wavelike
structures
broken (groove), oblique
oblique, growth rate changes, very narrow rings
broken, groove, tangential
oblique
broken (tongue), oblique, very wide rings
oblique
broken (groove), tangential
oblique, last 60 rings not measured (resin ducts)
oblique
broken (groove), rotted (tongue), oblique
broken (groove), oblique
broken (groove), oblique
broken (tongue + groove), oblique
radial
broken (groove), radial, surface damage (tongue), outer
6 rings not measured (on tongue)
broken (tongue & groove), oblique, wedging rings
broken (part of tongue), oblique, similar colour as BIR153
broken (groove), oblique, many resin bands
radial
tangential
broken (groove), oblique
broken (groove), oblique
broken (groove), oblique
broken (tongue), oblique
broken (groove), oblique, last 105 rings not measured (rings of
resin ducts)
oblique, last 68 rings not measured (very narrow, wedging rings)
17
New Zealand Tree-Ring Site Report 31
Table A2: Details of all unmeasured kauri samples obtained from Birkenhead Villa.
Key: sample = number of sample, timber type T & G = tongue & groove board, G & G = groove & groove board (used
for flooring of the veranda), dim. = dimension of sample cross-section, ring orientation (comments column) = oblique,
radial, tangential.
Sample
Timber type
Dim.
(mm)
Comments
Samples with broken tongue
BIR012
T & G -small
105 x 25
BIR014
T & G -small
105 x 25
BIR048
T & G -large
138 x 20
BIR055
T & G -large
138 x 20
BIR106
T & G -large
138 x 20
BIR108
T & G -large
138 x 20
BIR114
T & G -large
138 x 20
BIR115
T & G -large
138 x 20
BIR117
T & G -large
138 x 20
0
BIR124
T & G -large
138 x 20
tangential
tangential
tangential
oblique
oblique
oblique
oblique
tangential
tangential, very
strong mark rays
tangential
Samples with broken groove(s)
BIR004
T & G -small
105 x 25
BIR006
T & G -small
105 x 25
BIR008
T & G -small
105 x 25
BIR020
T & G -small
105 x 25
BIR041
T & G -large
138 x 20
BIR051
G & G -large
138 x 20
BIR056
T & G -large
138 x 20
BIR058
T & G -large
138 x 20
BIR060
T & G -large
138 x 20
BIR095
T & G -large
126 x 20
BIR098
T & G -large
123 x 20
BIR099
T & G -large
73 x 20
BIR100
T & G -large
138 x 20
BIR107
G & G -large
138 x 20
BIR111
T & G -large
138 x 20
BIR116
T & G -large
138 x 20
BIR120
G & G -large
138 x 20
BIR123
G & G -large
138 x 20
BIR130
T & G -large
138 x 20
BIR133
T & G -large
138 x 20
oblique
tangential
oblique
oblique
oblique
oblique
oblique
oblique
oblique
oblique
tangential
oblique, broken in half
oblique
oblique
tangential
tangential
tangential
oblique
oblique
oblique
Samples with broken tongue & groove
BIR040
T & G -large
138 x 20
BIR044
T & G -large
138 x 20
BIR046
T & G -large
138 x 20
BIR109
T & G -large
138 x 20
BIR112
T & G -large
138 x 20
BIR121
T & G -large
138 x 20
BIR122
T & G -large
138 x 20
BIR125
T & G -large
138 x 20
BIR126
T & G -large
138 x 20
tangential
oblique
radial
tangential
oblique
oblique
oblique
tangential
oblique
18
Sample
Timber type
Dim.
(mm)
Not broken (intact tongue & groove)
BIR010
T & G -small
105 x 25
BIR011
T & G -small
105 x 25
BIR016
T & G -small
105 x 25
BIR022
T & G -large
140 x 20
BIR025
T & G -large
138 x 20
BIR039
T & G -large
138 x 20
BIR059
T & G -large
139 x 20
BIR061
T & G -large
138 x 20
BIR063
T & G -large
139 x 20
BIR065
T & G -large
138 x 20
BIR066
T & G -large
138 x 20
BIR068
T & G -large
138 x 20
BIR089
T & G -large
138 x 20
BIR090
T & G -large
138 x 20
BIR091
T & G -large
138 x 20
BIR092
T & G -large
138 x 20
BIR093
T & G -large
138 x 20
BIR094
T & G -large
138 x 20
BIR096
T & G -large
138 x 20
BIR097
T & G -large
138 x 20
BIR101
T & G -large
138 x 20
BIR102
T & G -large
138 x 20
BIR103
T & G -large
138 x 20
BIR104
T & G -large
138 x 20
BIR105
T & G -large
138 x 20
BIR110
T & G -large
138 x 20
BIR113
T & G -large
138 x 20
BIR118
T & G -large
138 x 20
BIR119
T & G -large
138 x 20
BIR127
T & G -large
138 x 20
BIR128
T & G -large
138 x 20
BIR129
T & G -large
138 x 20
BIR131
T & G -large
138 x 20
BIR132
T & G -large
138 x 20
BIR134
T & G -large
138 x 20
BIR134
T & G -large
138 x 20
Comments
tangential
tangential
tangential
oblique
tangential
tangential
oblique
tangential
tangential
tangential
oblique
oblique
oblique
oblique
oblique
oblique
oblique
tangential
tangential
tangential
oblique
tangential
tangential
tangential
oblique
oblique
oblique
oblique
tangential
oblique
tangential
tangential
tangential
tangential
tangential
tangential
New Zealand Tree-Ring Site Report 31
Table A3: Details of all unmeasured non-kauri samples obtained from Birkenhead Villa.
Key: sample = number of sample, timber type T & G = tongue & groove board, ST = structural studs (used for flooring
of the veranda), ring orientation (comments column) = oblique, radial, tangential.
Sample
Timber type
Podocarpus totara*
BIR069
ST
BIR070
ST
BIR071
ST
BIR072
ST
BIR073
ST
BIR074
ST
BIR075
ST
BIR076
ST
BIR077
ST
BIR078
ST
BIR079
ST
BIR080
ST
BIR081
ST
BIR082
ST
BIR083
ST
BIR084
ST
BIR085
ST
BIR086
ST
Dim.
(mm)
Comments
100 x 51
90 x 44
90 x 44
90 x 44
90 x 44
90 x 44
92 x 43
92 x 43
90 x 44
91 x 49
91 x 49
90 x 44
90 x 44
92 x 44
90 x 44
90 x 48
93 x 49
100 x 73
pith included
tangential
tangential
oblique
tangential
broken, oblique
oblique
oblique
tangential
broken, oblique
broken, oblique
broken, oblique
tangential
oblique
tangential
oblique
oblique
broken, oblique
Pinus radiata
BIR168
T & G -large
137 x 18
BIR169
T & G -large
137 x 18
*species classification to be verified.
oblique
broken (tongue), oblique
19
New Zealand Tree-Ring Site Report 31
Table A4: Inter-tree comparisons of all trees in the site chronology BIRKa (COFECHA).
Best two matching positions for floating series - match shows last rings compared, number of rings (years), correlation coefficient and t-value. Stars between idents indicates t-statistic over 3.5. The second best matching position
(right of the dashed line) shows consistently lower correlation coefficients - and t-values – which further supports the
correct dating of the series.
1st series
2nd series
BIR166
*BIR035
1231
1231
BIR166
*BIR038
1231
1231
BIR166
*BIR045
1231
BIR166
*BIR088
BIR166
BIR035
Last ring compared
N (yrs)
Corr.
T-stat.
Last ring compared
65
0.56
5.3
1231
1123
65
0.64
6.6
1214
1311
1231
65
0.62
6.2
1231
1231
1231
65
0.5
4.6
*BIR153
1227
1227
61
0.9
*BIR038
1264
1264
166
0.86
BIR035
*BIR045
1251
1251
179
BIR035
*BIR088
1264
1264
BIR035
*BIR153
1227
BIR038
*BIR045
1251
BIR038
*BIR088
BIR038
N (yrs)
Corr.
T-stat.
61
0.37
3.0
48
0.37
2.7
1203
65
0.38
3.2
1231
1196
65
0.36
3.1
15.4
1231
1224
62
0.23
1.9
21.8
1124
1311
62
0.34
2.8
0.86
22.4
1104
1251
42
0.43
3.0
136
0.93
30.1
1230
1279
151
0.20
2.5
1227
65
0.57
5.5
1119
1227
57
0.34
2.7
1251
153
0.82
17.5
1311
1124
52
0.45
3.6
1279
1279
151
0.82
17.7
1164
1279
66
0.39
3.4
*BIR153
1227
1227
65
0.63
6.5
1199
1227
65
0.38
3.3
BIR045
*BIR088
1251
1251
123
0.84
16.8
1177
1279
105
0.27
2.8
BIR045
*BIR153
1227
1227
65
0.57
5.5
1199
1227
65
0.45
4.0
BIR088
*BIR153
1227
1227
65
0.5
4.6
1192
1227
64
0.36
3.0
Table A5: Inter-tree comparisons of all trees in the five-timber sequence BIRKb (COFECHA).
(For a detailed explanation see Table A4).
1st series
2nd series
BIR033
*BIR052
1454
1454
73
0.68
7.8
1469
1421
BIR033
*BIR057
1469
1469
73
0.83
12.5
1469
1449
BIR033
*BIR137
1469
1469
77
0.76
10.3
1440
BIR033
*BIR138
1454
1454
73
0.76
10
BIR052
*BIR057
1454
1454
58
0.62
BIR052
*BIR137
1454
1454
62
0.6
BIR052
*BIR138
1454
1454
94
BIR057
*BIR137
1474
1474
BIR057
*BIR138
1454
BIR137
*BIR138
1454
20
Last ring compared
N (yrs)
Corr.
T-stat.
Last ring compared
N (yrs)
Corr.
T-stat.
61
0.28
2.3
53
0.35
2.7
1474
59
0.29
2.2
1469
1427
68
0.34
2.9
5.9
1410
1475
50
0.4
3.0
5.8
1430
1474
70
0.31
2.7
0.89
18.4
1412
1454
52
0.42
3.3
78
0.81
11.9
1475
1441
49
0.29
2.1
1454
58
0.69
7.1
1475
1410
51
0.42
3.2
1454
62
0.59
5.6
1474
1448
82
0.3
2.8
New Zealand Tree-Ring Site Report 31
Table A6: Descriptive statistics for each individual series of the site chronology BIRKa (COFECHA).
Series = name of series, Time span = start and end date of series, No. years = total number of measurements in that
series, No. seg. = number of segments in that series, No. of flags = number of flagged segments in that series, Corr.
with master = correlation coefficient between each series and the master chronology (generated by COFECHA from
all other series, see Material and Methods, p.5). Unfiltered statistics = based on the raw measurements of the chronology, Filtered statistics = based on the data after COFECHA has used a 32-year spline function to each series,
Mean mt. / Max mt. = average and maximum ring-width measurements (in millimeters) for that series, std dev. =
standard deviation of the ring-width measurements (in millimeters) for that series, Auto corr. = autocorrelation of that
series, Mean sens. = mean sensitivity of that series, Max value = maximum computed ring-width index (mean = 1.0)
for that series, AR = order of the autoregressive modelling that was used to remove autocorrelation from the series
during detrending (from NOAA Paleoclimatology Program 2005).
Corr.
Unfiltered statistics
Filtered statistics
No.
No.
No.
with
Mean
Max
Std
Auto
Mean
Max
Std.
Auto
AR
seg.
flags
master
mt.
mt.
dev.
corr.
sens.
val.
dev.
corr.
()
Series
Time span
years
BIR035
1063 1264
202
8
0
0.908
0.51
1.22
0.208
0.312
0.37
2.69
0.461
-0.009
1
BIR038
1099 1311
213
8
0
0.853
0.51
1.24
0.203
0.292
0.38
2.44
0.367
-0.005
1
BIR045
1073 1251
179
8
0
0.876
0.58
1.32
0.217
0.257
0.37
2.54
0.416
-0.012
1
BIR088
1129 1279
151
6
0
0.849
0.59
1.55
0.239
0.336
0.39
2.66
0.448
-0.022
1
BIR153
1163 1227
65
3
0
0.707
0.98
2.17
0.421
0.369
0.46
2.58
0.487
-0.039
2
BIR166
1167 1231
65
3
0
0.715
0.97
2.51
0.521
0.594
0.44
2.54
0.458
-0.08
2
875
36
0
0.848
0.61
2.51
0.253
0.325
0.389
2.69
0.428
-0.018
Total or mean
Table A7: Descriptive statistics for each individual series of the five-timber sequence BIRKb (COFECHA).
(For a detailed explanation see Table A6).
Corr
No.
No.
years
seg.
No.
Filtered statistics
with
Mean
Max
Std
Auto
Mean
Max
Std
Auto
AR
master
mt.
mt.
sens.
val.
Dev.
corr.
()
Series
Time span
dev.
corr.
BIR033
1382 1469
88
3
0
0.846
0.80
1.57
0.309
0.642
0.24
2.61
0.589
0.007
1
BIR052
1361 1454
94
4
0
0.830
0.86
1.84
0.32
0.575
0.27
2.79
0.498
-0.004
2
BIR057
1397 1475
79
3
0
0.840
0.92
1.97
0.378
0.567
0.29
2.90
0.616
-0.001
2
BIR137
1393 1474
82
3
0
0.782
0.75
1.35
0.256
0.603
0.24
2.63
0.593
0.000
1
BIR138
1360 1454
95
4
0
0.867
0.87
1.84
0.292
0.573
0.24
2.85
0.542
0.012
2
438
17
0
0.834
0.84
1.97
0.310
0.592
0.258
2.90
0.565
0.003
Total or mean
flags
Unfiltered statistics
21