Academia.edu no longer supports Internet Explorer.
To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser.
Tree growth at polar latitudes based on fossil tree ring analysis
Tree growth at polar latitudes based on fossil tree ring analysis
Tree growth at polar latitudes based on fossil tree ring analysis
Tree growth at polar latitudes based on fossil tree ring analysis
Tree growth at polar latitudes based on fossil tree ring analysis
Patty Ryberg2007, Palaeogeography, Palaeoclimatology, …
Related Papers
Journal of the Geological Society
Leaf habit of Late Permian Glossopteris trees from high-palaeolatitude forests2014 •
Forests are expected to expand into northern polar latitudes in the next century. However, the impact of forests at high latitudes on climate and terrestrial biogeochemical cycling is poorly understood because such forests cannot be studied in the modern. This study presents forestry and geochemical analyses of three in situ fossil forests from Late Permian strata of Antarctica, which grew at polar latitudes. Stem size measurements and stump spacing measurements indicate significant differences in forest density and canopy structure that are related to the local depositional setting. For forests closest to fluvial systems, tree density appears to decrease as the forests mature, which is the opposite trend of self-thinning observed in modern forests. We speculate that a combination of tree mortality and high disturbance created low-density mature forests without understory vegetation near Late Permian river systems. Stable carbon isotopes measured from permineralized wood in these forests demonstrate two important points: (i) recently developed techniques of high-resolution carbon isotope studies of wood and mummified wood can be applied to permineralized wood, for which much of the original organic matter has been lost and (ii) that the fossil trees maintained a deciduous habit at polar latitudes during the Late Permian. The combination of paleobotanical, sedimentologic, and paleoforestry techniques provides an unrivaled examination of the function of polar forests in deep time; and the carbon isotope geochemistry supplements this work with subannual records of carbon fixation that allows for the quantitative analysis of deciduous versus evergreen habits and environmental parameters, for example, relative humidity.
Upper Permian silicified gymnosperm woods from the Bainmedart Coal Measures (Amery Group) near Beaver Lake, East Antarctica are described as two new species, Australoxylon bainii and A. mondii, on the basis of morphometric and qualitative characters – including ray anatomy, tracheid shape, and cross-field pit structure. Australoxylon mondii has two forms, one of which is characterised by a distinctive ray architecture comprising semidetached rows of ray cells with intervening gaps bridged by sporadic joins. Wood of Vertebraria could not be distinguished from Australoxylon mondii on microanatomical characters, which suggests that these two organ taxa may represent different parts of the same glossopterid plant. Many characters used traditionally in wood taxonomy could not be applied owing to substantial variation or preservational differences both within and between specimens. Three types of presumed biogenic cavities occur in the woods. Coprolite-containing cavities distributed in seasonal bands represent rare evidence for Permian wood-boring anhropods. Other, irregularly distributed cavities and appositions were probably formed by pathogenic fungi. Growth-ring analysis indicates a markedly seasonal climate with low to moderate interseasonal variation in wood production. Significant intraseasonal influences on growth are also evidenced by numerous false rings.
Wood decay of Xenoxylon yunnanensis Feng sp. nov. from the Middle Jurassic of Yunnan Province, China
A permineralised gymnosperm wood, Xenoxylon yunnanensis Feng sp. nov., is described from the Middle Jurassic Shaximiao Formation in Huize County, Yunnan Province, Southwest China. The pycnoxylic wood consists of thick-walled tracheids and thin-walled rays. It is characterised by uniseriate, contiguous, compressed bordered pits on the radial walls of tracheids, and one large simple pit in each cross-field. Growth rings exhibit narrow late-wood. The mean sensitivity of analysis of 25 growth rings is 0.2, suggesting that a climate with abundant rainfall and weak seasonality could have prevailed in Yunnan, at least locally, during the Middle Jurassic. The outer portion of the wood is largely decayed, and shows poorly preserved cells lacking details. Decayed tracheids displaying various features, including removal of middle lamellae, separations of secondary walls, presence of thickened corners and appositions, are recognised as cell reactions to fungal activity. Irregularly distributed micro-cavities are formed by complete decomposition of tracheids and rays in the wood. Abundant fungal remains occurring in the wood generally consist of multiple branched hyphae. These fungal hyphae are either confined to individual cell lumens or extend through adjacent cells. Although the probable reproductive structure and typical clamp connection are very rarely observed with few septate hyphae, the affinities of these fungal hy-phae are somewhat obscure. Nevertheless, our study sheds light on the palaeoecology of Middle Jurassic terrestrial ecosystems of Southwest China.
A B S T R A C T The early Permian Chemnitz Fossil Lagerstätte (Leukersdorf Formation, Chemnitz Basin, SE Germany) represents a diverse T 0 assemblage of a fossil forest ecosystem around the Sakmarian-Artinskian transition (290.6 ± 1.8 Ma), which was preserved by pyroclastic deposits of a multi-phased volcanic eruption. The multi-aged plant community consists of predominantly hygrophilous elements, which grew on an alluvial plain mineral substrate under sub-humid conditions, representing a wet spot environment. Strong seasonality triggered the formation of annual tree rings in arborescent woody plants, such as pycnoxylic gymnosperms, medullosan seed ferns and calamitaleans. From several hundred fossil trees, the 53 best-preserved specimens were selected and investigated in detail by measuring 2,081 tree rings in individual sequences of up to 77 rings. Ring sequences were analysed by standard dendrochronological methods to determine both annual growth rates and mean sensitivity. Morphological and statistical analyses on single tree rings reveal different tree-ring types according to the different plant groups. Pycnoxylic gymnosperms have distinct and regular tree rings, whereas medullosan seed ferns and calamitaleans show indistinct and regular tree rings as well as so called event rings. Results reveal differences between plant groups regarding their physiological reactions or adaptations to seasonal fluctuations. In comparison to pycnoxylic gymnosperms, both medullosan seed ferns and calamitaleans exhibit reduced growth rates and more sensitive reaction to environmental perturbances as water deficiency pointing to comparably lower adaptation to seasonally dry palaeoclimate. In this context, event rings are in many cases traced back to plant physiological stress during particularly severe drought periods. Altogether, these fossil trees serve as sensitive environmental archives, which shed light on growth conditions several decades back in time from the entombing eruption.
Review of Palaeobotany …
Modified basal elements in< i> Dicroidium</i> fronds (Corystospermales)2012 •
Petrographic imaging, in combination with qualitative and quantitative instrumental analyses of mineral mass, allow us to obtain material signatures of silicified plant stems that are relatively common in sediments of continental basins since the late Palaeozoic. These fossils can be found in their original strata but commonly have been removed from their environmental and stratigraphic context, redeposited, and scattered on the recent land surface after erosion of the parent rocks. Analytical data gathered from X-ray diffraction analysis, hot cathodoluminescence (CL) imaging and spectroscopy, electron microprobe analysis, Raman spectrometry, and polarised light microscopy serve to characterise material signatures of samples from basins in Brazil, Germany, the Czech Republic, Sultanate of Oman, Mongolia, Antarctica, France, and the USA. This collection includes silicified Pennsylvanian and Permian plant taxa (and a few from the Triassic) found in fluvial environments and sites influenced by volcanism with the purpose to discern fundamental material characteristics formed under particular environmental circumstances. Late Pennsylvanian and Permian silicified stems in fluvial rocks include the presence of well-crystalline quartz (α-SiO2), sometimes with a trace of kaolinite, showing weak CL (mostly blue or dark reddish), occasional mosaic or patchy preservation of anatomical details, and other signs of pressure distortion of wet trunks in fluvial deposits and subsequent diagenetic recrystallisation. The presumed silica source for the initial stage of silicification was weathering of labile minerals, mostly feldspars in the alluvium. In wood from aeolian deposits, moganite in combination with goethite was detected. Based on our results, we propose that the stems were silicified in sandy or gravelly fluvial deposits, most frequently in arkoses and arkosic sands, indicators of relatively warm climate with pronounced seasonal distribution of precipitation. Excluded from this interpretation are stems silicified primarily by volcanic material; these are distinguished by a higher species diversity, silicification close to the site of growth, miscellaneous mineralogy, usually with very colourful CL shades, and the presence of metastable forms of SiO2, opal-CT or moganite. This volcanic influence on silicification mode is less clearly controlled by seasonality of precipitation or palaeoclimate itself.
Available online at www.sciencedirect.com
Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246 – 264
www.elsevier.com/locate/palaeo
Tree growth at polar latitudes based on fossil tree ring analysis
Edith L. Taylor ⁎, Patricia E. Ryberg
Department of Ecology and Evolutionary Biology, and Natural History Museum and Biodiversity Research Center, University of Kansas,
1200 Sunnyside Ave., Lawrence, KS 66045-7534 USA
Received 29 December 2006; received in revised form 5 June 2007; accepted 14 June 2007
Abstract
Permineralized trunks and mature wood samples with well-preserved growth rings are described and analyzed from the Upper
Permian and Middle Triassic of the central Transantarctic Mountains. This fossil wood is unique in that the plants lived in an
environment with no modern analogue and exhibited luxuriant tree growth above 75°S paleolatitude. Ring width averages 1.69–
2.3 mm, with maximum width of 6.83–9.9 mm, an order of magnitude larger than ring widths produced at near-polar latitudes
today. Tree rings in both the Permian and Triassic woods show similar structure, consisting almost entirely of earlywood (spring
wood), with between 0–12% of each ring classified as latewood (summer wood). The small amount of latewood (0–6 cells)
indicates a very rapid transition to seasonal dormancy, probably in response to decreasing light levels at these paleolatitudes. In
order to accurately delimit the earlywood–latewood boundary, a comparison was done of classical dendroclimatological techniques
and alternative techniques utilized primarily by paleobotanists analyzing fossil woods. We found that classical wood anatomy
techniques provided a more accurate explanation of wood development and tree growth for these high-latitude samples. The
suggested cool-temperate Late Permian Glossopteris flora from this area differs substantially from the warm-temperate Middle
Triassic corystosperm flora (leaf type, Dicroidium) and very different paleoclimates have been reconstructed for these two time
periods. Ring structure and wood growth from both sites, however, are very similar, indicating that these plants were responding to
the environment in very similar ways. The structure of the tree rings, including a large number of earlywood tracheids and a very
low number of latewood cells, provides evidence that growth at these polar latitudes was limited by light levels rather than water
and temperature as occurs in modern high-latitude forests. These fossil tree rings have important implications for understanding
woody shoot growth and cambial function at high latitudes during periods of global warmth.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Late Permian; Middle Triassic; Antarctica; Tree rings; Paleoclimate; Gondwana fossil flora; Fossil wood anatomy
1. Introduction
Although currently glaciated, Antarctica was covered
in vegetation for much of its existence. Plant fossils have
been recorded from the Devonian (Edwards, 1990) until
⁎ Corresponding author. Fax: +1 785 864 5321.
E-mail addresses: etaylor@ku.edu (E.L. Taylor), rybergp@ku.edu
(P.E. Ryberg).
0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.palaeo.2007.06.013
the onset of the present glaciation in the Oligocene and
there is evidence of alpine-type assemblages as recently as
the Pliocene in continental Antarctica (Francis and Hill,
1996; Ashworth and Cantrill, 2004). Previous studies of
Antarctic floras (e.g., Taylor and Taylor, 1990; McLoughlin, 2001) record a floral transition from the Permian to the
Triassic similar to that observed elsewhere in Gondwana
(e.g., Rees, 2002; Gastaldo et al., 2005). During the Late
Permian the Antarctic landscape was dominated by the
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
Glossopteris flora, which has been described as a cooltemperate assemblage; glossopterid organs (leaves,
woody stems, etc.) at some sites represent upwards of
90% of the identifiable plant remains (Cúneo et al., 1993).
Floral records from the Lower Triassic of Antarctica are
scarce (McLoughlin et al., 1997; Retallack, 2005), but
throughout Gondwana there was a major floral turnover at
the Permian–Triassic boundary. The glossopterids disappeared almost completely (but see Delevoryas and
Person, 1975; McManus et al., 2002) and the Early
Triassic was dominated by new clades of pteridosperms.
By the Middle Triassic, corystosperm seed ferns were
dominant throughout Gondwana (Thomas, 1933; Retallack, 1980; Taylor and Archangelsky, 1985; Maheshwari
and Bajpai, 1996). The most common members of this
group include Dicroidium leaves, Umkomasia ovulate
organs, and Pteruchus pollen organs.
The central Transantarctic Mountains (CTM) region
has provided a wealth of information on Permian and
Triassic fossil biotas. Two deposits of permineralized
peat have yielded extraordinarily well-preserved plant
material and provided anatomical details on floral
assemblages from these periods (Taylor and Taylor,
1990). The Late Permian peat from Skaar Ridge consists
almost exclusively of glossopterid remains, while the
Middle Triassic peat from the Fremouw Formation
exhibits greater diversity (Taylor et al., 2000). In the
latter, all major groups of vascular plants are represented,
including four orders of seed plants (Table 1). Both
permineralized floras are similar in their floral composition to compression–impression floras of comparable
age from across Gondwana, although the Late Permian
flora is less diverse than those from lower latitudes.
Within the peat are numerous woody axes, including
stems and trunks, which exhibit well-preserved growth
rings. In addition, isolated wood samples and logs up to
20 m long are relatively common at the same site as the
Triassic peat. Because of the presence of the peat
deposits, much of the wood can be correlated with other
plant organs and assigned to taxonomic groups (e.g.,
Meyer-Berthaud et al., 1993; Del Fueyo et al., 1995).
Evidence of forest growth in Antarctica consists of
forests in growth position, silicified logs, and wood
samples; these have been found at a number of localities
ranging from the Permian through the Eocene (e.g.,
Jefferson, 1982; Francis et al., 1993; Falcon-Lang and
Cantrill, 2002; Cantrill and Poole, 2005; Poole and
Cantrill, 2006). Fossil woods with well-preserved
growth rings from several of these sites have been
analyzed in detail. Jefferson (1982) was the first to study
an Early Cretaceous fossil forest from Alexander Island,
Antarctic Peninsula (paleolatitude, ∼ 71°–72°S). This
247
Table 1
Permineralized peat floras, Central Transantarctic Mountains,
Antarctica
Skaar Ridge (Late Permian)
Glossopteridales— Glossopteris schopfii (leaves, stems)
Glossopteris skaarensis (leaves, stems)
Vertebraria (roots)
Araucarioxylon-type wood
Ovulate organs (2 types)
Additional seed plants— Plectilospermum elliotii (seeds)
Choanostoma verruculosum (seeds)
Bryophyta–Bryidae–Merceria augustica (leaves, axes, rhizoids)
Filicales–Skaaripteridaceae–Skaaripteris minuta
(stems, roots, sporangia)
Fungi–Basidiomycetes–white rot, pocket rot in woody axes
Zygomycetes (hyphae and chlamydospores)
Fremouw Peak (Middle Triassic)
Corystospermales— Dicroidium fremouwensis (leaves)
Kykloxylon fremouwensis (stems)
Jeffersonioxylon gordonense (woody stems)
Pteruchus fremouwensis (pollen organ); pollen ultrastructure
Rhexoxylon-like axis
Umkomasia resinosa (cupules, ovules)
Petriellales— Petriellaea triangulata (ovulate cupules)
Coniferales–Podocarpaceae–Notophytum krauselii (stems, roots,
leaves)
Taxodiaceae— Parasciatopitys aequata (seed cones)
Voltziales— Leastrobus fallae (pollen cones)
Cycadales— Antarcticycas schopfii (stems, roots, cataphylls, leaves)
Delemaya spinulosa (pollen cones)
Additional seed plants— Ignotospermum monilii (isolated seeds)
Filicales–Cyatheaceae?/Pteridaceae?–Schopfiopteris
repens (rhizomes)
Gleicheniaceae— Gleichenipteris antarcticus (sporangia)
Gleicheniaceae?— Antarctipteris sclericaulis (rhizomes)
Matoniaceae— Tomaniopteris katonii (sori, sporangia)
Matoniaceae?— Soloropteris rupex (stems)
Osmundaceae— Ashicaulis (Osmundacaulis) beardmorensis
(stems)
Ashicaulis woolfei (stems, frond fragments)
Other ferns: Fremouwa inaffecta (rhizomes)
Schleporia incarcerata (stems)
Marattiales— Scolecopteris antarctica (pinnules, sporangia)
Equisetales— Spaciinodum collinsonii (stems, buds, branches)
Incertae sedis— Hapsidoxylon terpsichorum (stems)
Fungi–Basidiomycetes–Palaeofibulus antarctica
Wood rot in Araucarioxylon
Zygomycetes (Endogonales–endomycorrhizae):
Vesicular–arbuscular mycorrhizae
Sclerocystis-like
Mycocarpon asterineum
Endogone-like zygospores; Glomus-like chlamydospores
Gigasporites myriamyces, Glomites cycestris
Trichomycete
Ascomycetes?— Endochaetophora antarctica
Chytridiomycetes— endobiotic resting spores
For a more detailed list, including references, see Taylor et al. (2000).
248
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
material was subsequently studied by other investigators
(Creber and Francis, 1987; Creber, 1990; Falcon-Lang
et al., 2001), who found that the productivity of this
polar forest was similar to forests in temperate latitudes
today. Francis and colleagues (Francis et al., 1994)
analyzed wood from the Weller Coal Measures (late
Early Permian) of the Allan Hills in southern Victoria
Land (paleolatitude, ∼ 80°–85°S) and noted wide
annual rings indicative of an equable growing season
at these high latitudes during this period. Examination of
tree rings in Cretaceous and Tertiary wood from the
Antarctic Peninsula also revealed extensive secondary
growth (Francis, 1986; Francis and Poole, 2002). These
studies, along with data from compression–impression
floras, indicate that much of the continent was vegetated
for most of its history, even when situated at very high
paleolatitudes.
During the late Paleozoic, the paleo-South Pole is
commonly reconstructed as situated on the Antarctic
continent (Grunow, 1999; Scotese, 2002). Late Permian
paleogeographic reconstructions place it either in
Northern Victoria Land (Antarctica) or in southeastern
Australia. Either of these interpretations would place the
CTM at very high latitudes in the Late Permian,
certainly above 75°S, and probably between 80°–
85°S. During the Triassic, Antarctica rotated slightly
away from the pole, but the central Transantarctic
Mountains were still situated at high paleolatitudes
during the Middle Triassic (∼70–75°S). During this
time, Gondwana was in transition as the climate
changed from icehouse conditions of the Early Permian
to a strong greenhouse climate by the Middle Triassic
(e.g., Kidder and Worsley, 2004; Galfetti et al., 2007).
Fossil forests in the central Transantarctic Mountains
during the Permian and Triassic were located at slightly
higher paleolatitudes than those described from southern
Victoria Land (Francis et al., 1994), and thus represent
the highest paleolatitude wood available for ring
analysis from Antarctica (see also Cúneo et al., 2003).
At these extreme latitudes, trees were growing in a
strongly seasonal polar light regime, thus ensuring that
growth ring boundaries were formed annually. Although
the mid-Triassic Antarctic flora may still have been in a
period of recovery from the end-Permian extinctions, to
date there have been very few analyses of fossil tree
rings from the Triassic of Gondwana (Gabites, 1985;
Pires et al., 2005).
In this study we present an analysis of tree rings in
Late Permian and Middle Triassic wood from the central
Transantarctic Mountains. The Late Permian wood
belongs to the plant that bore Glossopteris leaves by
correlation with leaves in the peat at the site (Pigg and
Taylor, 1993), and because glossopterids are the only
known woody plants in the low diversity flora of Skaar
Ridge. The most common wood type in the Middle
Triassic Fremouw Formation belongs to the corystosperms, and represents the stem of Dicroidium (Kykloxylon,
Meyer-Berthaud et al., 1992, 1993; Jeffersonioxylon, Del
Fueyo et al., 1995). Due to the exceptional preservation of
this material, it is possible to compare ring structure from
these two time periods. These specimens not only span a
time of great floral turnover, but also provide a record of
climate change during an important transitional phase in
Earth history.
2. Materials and methods
Silicified stems and trunks (Figs. 1–3) were collected
from peat deposits and as isolated specimens at Skaar
Ridge, McIntyre Promontory, and Fremouw Peak in the
region of the Beardmore and Shackleton Glaciers,
central Transantarctic Mountains. Most of the specimens
are portions of larger axes with only a few containing
preserved pith; none of the specimens had preserved
extraxylary tissues. Specimens were collected during the
1990–1991, 1995–1996, and 2003–2004 Antarctic field
seasons. The Skaar Ridge peat (84° 49′ 15.8″ S, 163° 20′
18.9″ E, Buckley Island quadrangle, Barrett and Elliot,
1973) (Taylor et al., 1989) occurs within the Upper
Buckley Formation of the Beacon Supergroup and is
considered to be Late Permian in age based on
palynomorphs and associated compression floras (Farabee et al., 1991). A single, large trunk was collected
from McIntyre Promontory (84° 22′ 23″ S, 179° 45′ 58″
E) during the 1995–1996 field season (Fig. 4). The forest
level, where six specimens were found in growth
position on the side of a steep cliff face, occurs near
the base of the Upper Buckley Formation and is probably
Middle–Late Permian (J.L. Isbell, personal communication; Taylor et al., 1997). Due to the difficulty of
collecting at this locality combined with the weight of the
trunks, only the smallest specimen at the site (no. 12,389,
35.2 cm in diameter) could be retrieved. Triassic peat and
wood samples were collected from the col north of
Fremouw Peak (84° 17′ 24.1″ S, 164° 21′ 24.2″ E)
(Taylor et al., 1989). This deposit has been dated as early
Middle Triassic based on palynomorphs preserved in the
peat (Farabee et al., 1990).
All specimens were prepared using the acetate peel
technique (Galtier and Phillips, 1999), after etching
polished surfaces in concentrated (48–50%) hydrofluoric acid. Selected peels were examined using transmitted
light and photographed with a Leica DC500 digital
camera. Peels were mounted in Eukitt® on microscope
249
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
Table 2
Late Permian tree ring measurements (see text for explanation of values in parentheses)
Specimen #
Peat/trunk
12,389
13,089
13,090
13,691
15,485
15,503
15,512
15,514
Average
Trunk
Peat
Peat
Peat
Peat
Peat
Peat
Peat
Specimen width (cm)
Total # of rings
Maximum width (mm)
Minimum width (mm)
Mean width (mm)
MS
32.5
9.4
7.4
8.3
13.8
7.4
4.1
6.0
9.3
27 (115)
45 (59)
53 (92)
30
16
27
15
25
23 (47)
5.12
2.27
1.68
3.56
9.90
4.13
2.21
3.34
4.03
1.03
0.36
0.20
0.90
2.46
0.73
0.53
0.95
0.90
2.45
1.11
0.82
2.02
6.49
2.15
1.27
1.81
2.27
0.30
0.32
0.37
0.37
0.32
0.34
0.33
0.35
0.34
slides for photography. All specimens, peels and slides
are deposited in the Paleobotanical Collections, Natural
History Museum and Biodiversity Research Center,
University of Kansas, under the specimen numbers
listed in Tables 2 and 3 (http://paleobotany.bio.ku.edu/
PaleoCollections.htm). Wright Cell Imaging Facility's
ImageJ software (Rasband, 1997–2004) was used to
measure ring widths and radial cell diameters. Ringwidth measurements were made along a single radius,
but in some cases, due to poor cellular preservation,
measurements continued along an adjacent radius to
obtain the largest number of ring measurements. Some
rings within an otherwise well-preserved trunk were too
crushed to measure ring width, so these particular rings
were excluded from analysis. Since the earliest formed
rings in stems generally record rapid and variable
growth (e.g., Fritts, 1976), the innermost 3–20 rings, the
so-called juvenile wood, were excluded from the
analysis. In addition, the outermost ring was not
measured as the ring boundary was often not preserved.
Therefore, the total number of rings listed in Tables 2
and 3 represents a conservative minimum. Radial cell
diameters were obtained by measuring cells across a
single ring from one ring boundary to the next. Two
rings per specimen were measured, one file of cells in
each ring, one ring towards the middle of the wood and
one towards the periphery.
Analyses performed included calculating standard
mean sensitivity (Fritts, 1976) and the cumulative sum
equation of Creber and Chaloner (1984). Annual
sensitivity is a measure of variability in ring width
from year to year and mean sensitivity represents variability over the lifespan of the tree. Mean sensitivity
(MS) estimates the variability in ring width from
Table 3
Middle Triassic tree ring measurements
Specimen #
Peat/trunk
11,208
11,313
11,468
11,475
11,491
11,619
11,800
11,816
11,822
11,823
12,820
12,961
12,963
12,964
12,965
13,007
13,009
13,032
13,655
13,802
13,823
Average
Peat
Peat
Trunk
Trunk
Peat
Trunk
Peat
Peat
Peat
Peat
Peat
Peat
Peat
Peat
Peat
Peat
Peat
Trunk
Trunk
Trunk
Trunk
Specimen width (cm)
Total # of rings
Maximum width (mm)
Minimum width (mm)
Mean width (mm)
MS
3.5
5.7
9.5
15.3
8.1
6.7
6.0
8.2
8.8
7.4
10.4
7.5
11.5
11.4
7.6
2.1
7.1
18.0
13.6
11.3
9.8
9.0
26
8
77
53
8
62
68
54
39
14
50
58
105
122
72
31
78
78
136
43
117
61.86
3.92
6.83
2.73
3.69
4.52
1.05
3.23
5.8
4.18
5.83
2.92
4.00
3.61
2.88
2.51
1.01
1.85
4.73
2.24
5.54
2.80
3.61
0.24
4.27
0.08
0.99
1.89
0.19
0.18
0.17
1.27
2.18
0.88
0.32
0.22
0.15
0.37
0.32
0.29
0.42
0.12
0.17
0.13
0.71
1.32
5.30
1.07
2.16
3.78
0.57
0.82
1.22
2.36
4.41
1.88
1.44
1.02
0.98
1.08
0.65
0.79
2.25
0.58
1.19
0.70
1.69
0.34
0.13
0.35
0.22
0.24
0.24
0.40
0.42
0.22
0.14
0.23
0.29
0.35
0.45
0.42
0.21
0.25
0.35
0.44
0.42
0.36
0.31
250
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
one year to the next over the life of the tree using the
formula:
X
MS ¼ ð1=n 1Þ
ðj2ðxtþ1 xt Þ=ðxtþ1 þ xt ÞjÞ
where n equals the number of rings in the specimen, x the
width of a ring, and t the ring number. Mean sensitivity
values range from 0 to 2. Wood with values of 0–0.3 is
considered complacent, i.e., showing little response to
environment, while sensitive trees, those seasonally
affected by environmental variables, range from 0.3–2
(Fritts, 1976). Although mean sensitivity as a measure of
tree environmental response has been questioned in recent
years, due to the difficulty of knowing what part of the tree
is represented by fossil wood samples (Falcon-Lang,
2005a), we calculated it for comparison to previous fossil
tree ring studies which utilized this method (Francis,
1986; Francis et al., 1994).
The cumulative sum equation, defined as the cumulative sum of tracheid radial cell diameters as they deviate
from the mean (CSDM) across a single ring, was proposed
by Creber and Chaloner (1984). This method has been
used in fossil wood as a method of defining the
earlywood–latewood (EW–LW) boundary in wood and
as a way to classify ring series by climate (e.g., Creber and
Chaloner, 1984; Falcon-Lang, 2000, 2005a):
S i ¼ Si
1
þ ðxi
xave Þ
where Si is the cumulative sum of the radial cell diameters,
Si−1 the cumulative sum of the previous cell diameter, xi
radial cell diameter, and xave the mean of radial cell diameters in that ring. In this paper, the cumulative sum calculation was used only to provide a point of comparison
among different growth environments based on ring
anatomy, as suggested by Creber and Chaloner (1984; see
also Brison et al., 2001). In the present study, EW–LW
boundary was determined using Mork's (1928) definition,
for which Denne (1989) has provided two interpretations
that are commonly used in wood anatomical studies. In
the first formula, latewood is defined as the point where
radial cell wall thickness of an individual tracheid is equal
to or greater than four times the width of the cell lumen:
2azb
ðFormula 1Þ
where a = wall thickness of two adjacent cell walls, and
b = lumen radial diameter. In the second formula, wall
thickness must be at least twice the lumen diameter of that
cell for it to be considered latewood:
2czb
ðFormula 2Þ
where c = thickness of a single cell wall, and b = lumen
radial diameter. To evaluate the utility of these two
definitions in fossil material, we calculated the EW–LW
boundary using both of Denne's (1989) interpretations.
These EW–LW determinations were then compared to
the cumulative sum method to determine which formula
best defined wood growth and its relationship to the
paleoenvironment for the Antarctic specimens.
Using the cumulative sum calculation as a starting
point, Falcon-Lang (2000) presented a method to
determine whether a gymnospermous wood specimen
belonged to an evergreen or a deciduous plant. In his
method, when the apex of the CSDM curve occurs to the
right of the center of the curve, the plant is evergreen,
while deciduous species generally fall to the left of
center (Falcon-Lang, 2000, text-Fig. 4). This method
was also applied to the Antarctic specimens and compared with data from other methods for determining
deciduousness in woody fossil plants.
3. Results
3.1. Permian wood
Eight stems were analyzed from the Permian: seven
from the Skaar Ridge peat and one isolated trunk from
McIntyre Promontory; all specimens represent stem
wood. Since glossopterids are the only woody plants
present in this flora, root wood from the peat is identifiable either as the distinctive Vertebraria type, with
wedges of wood separated by air spaces or, if it is of the
‘solid cylinder’ type of Vertebraria (Neish et al., 1993),
by the large number of faint and discontinuous rings.
None of the specimens detailed here exhibited these
characteristics, so all specimens are considered to be stem
wood. The axes ranged from 4.1–35.2 cm in diameter
with 15–115+ rings per specimen and an average of 47
rings (Fig. 4). In three specimens, poor preservation prevented measurement of all rings, so values for ring widths
represent only the well-preserved rings. The ring boundary is usually visible even in poorly preserved rings, so
the total number of rings could be counted (Table 2,
number in parentheses). Individual ring widths ranged
Figs. 1–5. Permian and Triassic wood from Antarctica. Fig. 1. Large, permineralized trunk preserved in sandstone, Middle Triassic, Fremouw Peak
(∼ 22 m long). Fig. 2. Partially upright stump in channel sandstone, Middle Triassic, Fremouw Peak (∼30 cm in diameter). Fig. 3. Large trunk from
McIntyre Promontory showing flaring base. Bar scale in cm. Fig. 4. Cross section of trunk in Fig. 3 showing well-preserved growth rings; rings were
somewhat compacted during the preservational process. #12,389. White areas represent regions of poor preservation. Fig. 5. Cross section of Permian
wood from Skaar Ridge. Center of trunk to left; cambium to right. Arrow = true ring boundary; arrowheads = false rings. #15,485G, slide 15,485γ, Bar
scale = 0.3 mm.
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
from 0.20–9.9 mm (mean = 2.3 mm, Table 2). False rings
were observed in only one specimen (15,485) and were
identified by a progressive thickening of tracheid cell
251
walls, followed by a gradual thinning, with no ring
boundary or cessation of growth to signify the end of a
growing season (Fig. 5). Although it is often impossible to
252
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
determine whether fossil tree rings represent yearly
growth increments, the high paleolatitudes of these
deposits and the structure of the rings themselves support
the hypothesis that each ring represents a single year's
growth, so the number of rings therefore represents the
minimum age of the tree.
Perhaps the most interesting aspect of these Permian
woods is the large number of cells per ring and the small
amount of latewood. The number of earlywood cells per
ring varied greatly, from 34–234 cells (mean = 119), but
the number of latewood cells was always small, from 1–
5 cells per ring using Formula 1. One specimen (15,485)
had wider rings than the others with 236–238 cells per
ring. When this extreme value is excluded, cell numbers
range from 36–91 cells per ring (mean = 64). Mean
sensitivity of the Permian wood ranged from 0.30–0.37
with a mean of 0.34, and all specimens were classified
as “sensitive” (Table 2). Only three specimens (15,485,
15,503, and 15,514) had adequate cellular preservation
for tracheid radial diameter measurements. The others
were either partially crushed or, more commonly, the
cell walls were difficult to resolve, possibly due to
incomplete permineralization. Cell diameters ranged
from 11–294 μm (mean = 96 μm). Specimen 15,485
also had extremely large cell diameters, ranging from
27–294 μm. With values far from the other specimens,
15,485 may be responding to the environment in a
different way or it may consist of rapidly growing
juvenile wood. If this specimen is excluded from the
analysis, the range of cell diameters falls to 11–166 μm.
Using Creber and Chaloner's (1984) CSDM method, the
amount of latewood per ring is very large (all cells to the
right of the arrows in Fig. 6A), ranging up to 47% of the
ring for all specimens. Using either one of Denne's
(1989) two formulae for calculating the amount of
latewood (Fig. 6B), it is clear that the decrease in
tracheid radial diameter during the growing season is a
result of a gradual reduction in lumen diameter and not a
thickening of the tracheid walls. Tracheid wall thickness
varies slightly throughout the growing season, but
remains very close to the wall thickness in the first cells
produced in the spring (Fig. 6B). These results confirm
that the majority of cells in each ring represent
earlywood and not latewood (Fig. 7). Using this method,
the number of latewood cells for all specimen ranges
from 0–10% of each ring.
3.2. Triassic wood
Twenty-one axes ranging from 2.1–18.0 cm in
diameter were analyzed from the Middle Triassic
Fremouw Formation (Fig. 8). Seven of these included
pith tissue and these ranged from 6.7–18.0 cm in diameter. The number of rings per specimen was 14–136
(mean = 65) (Table 3; specimens with b 14 rings were
not included in the analysis). Ring widths varied from
0.08–6.83 mm (mean = 1.69 mm) (Table 3, Fig. 9). Due to
crushing at ring boundaries, which was common in many
of the specimens, only eight Triassic wood specimens
were used for cell analysis. As in the Permian wood, there
was a large amount of earlywood (14–104 cells) and only
a few cells of latewood (0–6 cells, Formula 1) to mark
seasonal boundaries (Fig. 10). One trunk specimen
(11,475) contained frost rings (Figs. 11, 12) and two
axes from the permineralized peat (12,963, 12,964) contained false rings. Mean sensitivities ranged from 0.14–
0.45 with an average of 0.31. Approximately half of the
stems would be classified as sensitive (Table 2). On
average there were 45 cells per ring (range from 14–104).
Cell diameters ranged from 11–97 μm (mean = 45 μm).
As with the Permian wood, the CSDM calculation shows
a gradual diminution of tracheid radial diameter across
each ring (Fig. 13A). Based on our data (Fig. 13B), this
size reduction is the result of narrowing cell lumens, rather
than an increase in wall thickness, as would have been
expected with the formation of latewood. The amount of
latewood in the Triassic rings ranged from 0–12% using
Denne's (1989) Formula 1.
4. Discussion
4.1. Comparison of Permian and Triassic wood
Although there are many similarities between the
Late Permian and Middle Triassic wood from the central
Transantarctic Mountains, the total number of tree
rings, on average, is much greater in the Triassic wood
than the Permian (∼ 62 vs. 23 average number of rings;
Tables 2, 3) indicating a more mature forest in the
Triassic than the Permian. There are several other
possible explanations for this difference. With one
exception, the Permian woods are all preserved in
permineralized peat, whereas the Triassic samples from
Fremouw Peak are derived from a broader paleoenvironment, including stems in peat nodules, and trunks
found in braided river deposits. Wood can be transported
for some distance by a river system, especially under
flood conditions (Fritz, 1980), so the Fremouw wood
may provide a proxy record for a different microenvironment. It is also possible that larger trunks were
simply not preserved in the Permian peat as they were in
the varied depositional environments of the Triassic
wood. As noted in Table 2, several Permian specimens
(12,389, 13,089, and 13,090) were too crushed to allow
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
253
Fig. 6. Different methods of calculating EW–LW boundary using Permian fossil wood (Skaar Ridge). A. CSDM method of Creber and Chaloner
(1984). The two graphs show results for two specimens, with two rings measured in each specimen (black and grey lines). EW–LW boundary = the
point at which each line turns toward zero (arrows). B. Denne's (1989) two methods based on the same two specimens in A. Thin grey line = 2a of
Formula 1; thin black line = 2c of Formula 2. EW–LW boundary = the point at which either thin line crosses the thick line (arrow) (see text for further
explanation).
tree ring analysis on the entire cross section. If the
estimated totals (i.e., those in parentheses) are included,
the average number of rings increases to 47, indicating
similar maturity of Permian and Triassic trees at time of
preservation. The trunk with the largest estimated
number of rings 12,389 (∼115), is from the forest site
on McIntyre Promontory. In addition, this specimen was
the smallest of six standing trunks, indicating that
mature forests were growing in Antarctica by the midPermian (Taylor et al., 2000). In contrast, the wood from
the Skaar Ridge Permian peat includes only one
stem with N 90 rings, and the rest have fewer than
45. The wood from Fremouw Formation includes four
specimens with more than 100 rings and these occur as
both peat specimens and isolated trunks in a fluvial
sandstone. With the relatively small sample size from
the Permian, concluding that trees grew to greater
maturity in the Triassic than in the Permian is premature.
It is clear, however, that mature trunks can be preserved
in silicified peat deposits based on the large number of
rings in some of the Triassic woods from the Fremouw
peat.
Ring width averaged 2.3 mm in the Permian samples,
but only 1.69 mm in the Triassic wood, even though the
Middle Triassic has been reconstructed as warmer than
the Late Permian (Kidder and Worsley, 2004; Woods,
2005). The results obtained in this study, however, are
probably skewed by the low number of Permian stems
analyzed as well as by the single Permian specimen
(15,485) with very large rings. If ring widths from
15,485 are excluded, the average ring width for Permian
wood is only 1.66 mm, similar to those from the Triassic.
Trees in high latitudes today, e.g. Alaska (Oswalt, 1950,
1952; Giddings, 1951) or subarctic Manitoba (Girardin
et al., 2005), generally produce b 1.0 mm of ring growth
each year. The width of the Antarctic tree rings is similar
to those produced in a temperate climate rather than a
polar climate of today. The size of the fossil growth rings
indicates that these trees were growing with adequate
water availability and moderate temperatures throughout
the growing season. The small proportion of latewood in
these fossils (Figs. 6B, 13B), however, does not occur in
any extant species and supports the reconstruction of a
growth environment limited by light availability and
characterized by a rapid end to the growing season (see
4.6 below). False rings were found in one Permian
(15,485) and two Triassic (12,963 and 12,964) specimens and frost rings in only one Triassic (11,475) trunk.
254
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
False rings form in extant wood in response to some
environmental perturbations—most commonly drought,
but also insect attack or partial defoliation. They can be
distinguished from true growth rings by the occurrence
of thicker-walled cells followed by production of typical
earlywood, without a true cessation of growth as is evident at a ring boundary (Fig. 5). The radial rows of
tracheids continue through a false ring, but stop at a ring
boundary. In addition, false rings are often discontinuous
around the circumference of the stem. Frost rings were
identified by a disruption in the orderly production of
cells by the cambium (Figs. 11, 12).
Frost rings form in extant plants when there is an
unseasonable frost during the growing season. Most
frost rings occur early in the spring when the cambium is
growing rapidly, but can also occur in the early autumn
before winter dormancy. Some or all of the cambial cells
are killed by the cold and as the meristem begins to
recover from this trauma, the first daughter cells are
often large and misshapen, and not in well-defined
radial rows (Fig. 11). Eventually, the cambium recovers
completely and tracheids appear in regular radial files
as they did prior to frost ring formation (Fig. 12).
Several authors have noted that frost rings are more
common in twigs and in young shoots (e.g., Chapman,
1994; Falcon-Lang, 2005a). The Triassic wood that
exhibits the frost ring disruption, however, was a large
specimen with 53 rings collected from the channel
sandstone on Fremouw Peak, so it may have been
moved to this location from higher altitudes upstream
before fossilization. The presence of false and frost
rings indicates that some unseasonal disruption occurred in these environments. The small number of
specimens with either type of ring, however, suggests
that perhaps unusual climatic events were not a common occurrence.
Comparing values for mean sensitivity (MS), the
Permian woods all show N 0.30 MS, indicating a
seasonal response to climate. The Triassic woods,
however, vary from 0.13–0.45 MS, so some would be
classified as sensitive (i.e., N 3.0), while others are
complacent. Unlike the Permian wood, only 52% of the
Triassic specimens could be classified as sensitive,
suggesting perhaps a more stable growth environment,
or trees less responsive to climatic changes. The lowest
Triassic sensitivities (i.e., in the ‘complacent’ range)
occur in samples with very few rings, indicating that
perhaps a larger sample taken from a known stem height
of more mature specimens is needed for an accurate
representation of mean sensitivity. In studies of extant
tree rings, the first 50 years of growth are generally
excluded from the analysis, due to the variability of
growth in the so-called juvenile stages (Fritts, 1976;
Schweingruber, 1988). The more mature the tree, the
more pertinent the mean sensitivity value is to a tree's
growth response. Excluding those fossil specimens with
b50 rings reduces the sample size considerably, but the
range of sensitivities is still 0.22–0.45 (mean 0.35).
Ring width is determined both by intrinsic (i.e.,
genetic) and extrinsic factors. Some trees respond
regularly to changes in temperature, water availability,
etc. in the environment. Other trees however, record
few sensitivity changes throughout the life of that tree
(Fritts, 1976). Modern dendrochronology and dendroclimatology analyses are most commonly based on
trees at the limit of their growth range, i.e. near treeline,
in areas with regular droughts, etc., rather than on trees
growing on optimal sites where water availability
does not fluctuate much from year to year. Since the
Antarctic trees were growing at polar latitudes, it is
impossible to speculate on the actual limits of their
growth range, although they were growing in an
environment with a low angle of sunlight throughout
the growing season. The most plausible explanation for
the range of sensitivities in the Triassic specimens is
that the specimens represented different microenvironments since they were collected from both peat
deposits and fluvial sandstones. The range of sensitivity values in the Triassic wood could also be attributed
to the presence of more than one natural taxon, each of
which may have responded differently to environmental perturbations. All of the wood described in the
present study is of the Dadoxylon-type, which provides
little information on the affinities of the wood except
that it is gymnospermous. The diversity of plants from
the Triassic peat (Table 1) is much greater than the
Permian peat and includes groups that are known to
produce large amounts of secondary xylem, e.g.,
Figs. 7–12. Permian and Triassic tree rings. Center of stem towards bottom of figures; outside of stem towards top (all represent peel preparations).
Fig. 7. Cross section of Permian wood showing ring boundary (arrows) and small amount of latewood (∼ 1–3 cells). #13,090B, slide 13,090β,
Scale = 40 μm. Fig. 8. Cross section of Triassic trunk, showing preservation from center of stem and large growth rings. Scale bar in cm. #11,475E.
Fig. 9. Cross section of Triassic wood showing fairly uniform ring growth and small amount of latewood before each ring boundary. #11,475E,
Scale = 2.3 mm. Fig. 10. Detail of Triassic ring boundary showing 1–2 cells of latewood (arrows). #13,007A, slide 13,007α Bar scale = 20 μm. Fig.
11. Higher magnification of frost ring in Fig. 12 showing disruption of radial files of tracheids. #11,475A, slide 11,475β Scale = 0.5 mm. Fig. 12.
Cross-section of Triassic wood showing frost ring (center) and true ring boundaries (arrows). #11,475A, slide 11,475α. Scale = 0.7 mm.
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
conifers and corystosperms. The Antarctic corystosperms produced wood that was very similar to that of
some conifer families (Meyer-Berthaud et al., 1992,
255
1993; Del Fueyo et al., 1995), making identification of
the wood somewhat problematic. To date, however,
only corystosperm foliage has been found associated
256
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
with large trunks (Del Fueyo et al., 1995; Cúneo et al.,
2003). Another explanation for the range of sensitivities in the Triassic samples may be that the local
environment was more variable than in the Permian.
Even though the plants occurred in a peat-forming
environment, there is evidence that the water level in
the Triassic peat did fluctuate, based on the presence of
phi layers in some roots (Millay et al., 1987). These
layers are formed in some modern conifers that live in
areas with a fluctuating water table (Gerrath et al.,
2005).
Ontogenetic age may also be a variable in the wide
ranges of mean sensitivity and ring widths seen in some
fossil woods. Falcon-Lang (2005b) notes that juvenile
wood tends to be more variable in terms of sensitivity
when compared with more mature wood. The term
‘juvenile’ is something of a misnomer, as all wood
represents mature xylem cells. Juvenile wood is simply
the wood which formed during rapid, early growth of
the saplings, and is also called crown wood (Larson
et al., 2001). This wood typically shows more variability
in a number of factors, including ring width. Since we
attempted to use standard dendrochronological techniques as much as possible, the innermost rings in axes
that contained a core of juvenile wood were excluded
from analysis, so this variable was controlled as much as
possible in the present analysis. With all of these
variables potentially affecting mean sensitivity values,
the values in this study represent a base line analysis of
mean sensitivity with the knowledge that other factors
not accounted for here may be affecting the results.
Given that both the Triassic and Permian plants were
growing at very high latitudes in a strongly seasonal
environment, the number of cells produced per ring is
quite large: an average of 64 in Permian woods (238
max) and 45 in Triassic specimens (104 max), another
measure of the favorable environment for tree growth.
Francis et al. (1994) found rings with up to 194 cells in
Permian wood from the Allan Hills, Antarctica. Larix
sibirica, a temperate wood found at high latitudes today
(∼ 70°–72°N), produces b20 cells in a growing season
(Taylor and Putz, 1993). This large difference indicates
either a longer growing season or more favorable
conditions for growth, i.e., readily available water and
higher temperatures for the Antarctic fossil wood than
high-latitude extant trees. Francis et al. (1994) estimated
a growing season of at least 48 days during the late Early
Permian in Antarctica based on Creber and Chaloner's
(1984) measurement of the production of up to four cells
per day in some extant spruce. Among living trees at
high latitudes, Oswalt (1960) found that the cambium
produced cells for only 50–60 days at one site in Alaska,
whereas an even shorter growing season (∼ 30 days)
was measured at another site (Giddings, 1942). The
calculated growing season for the present study would
be at most 58 days in the Permian and 26 days in the
Triassic, based on a maximum growth rate of four cells
per day. Gregory and Wilson (1968), however, found
that the same species (Picea glauca) growing in Alaska
and New England produced the same number of cells
each growing season, even though the growing season
in Alaska was about half as long. They found that the
cambium in the Alaskan trees had a higher rate of cell
production. Based on these results, it is difficult to
estimate the length of the growing season based only on
wood production. The large number of cells in the fossil
wood, however, indicates that Antarctica's growing
season in both the Permian and Triassic was longer than
that seen at high latitudes today, which has important
implications for understanding the environmental factors that limited tree growth during times of global
warmth vs. today (see below).
4.2. Earlywood–latewood boundary
The Permian and Triassic woods from the CTM
exhibit relatively wide growth rings indicating overall favorable growing seasons during both time periods.
More importantly, the structure of the rings is fundamentally different from temperate or high-latitude rings
produced in extant plants, as the fossil rings consist
almost entirely of earlywood with only a small proportion
of latewood. There has been much discussion in the
literature on determining the EW–LW boundary in tree
rings (e.g., Creber and Chaloner, 1984; Denne, 1989, and
papers cited therein). Creber and Chaloner determined the
boundary by graphing the cumulative sum of deviations
from the mean (CSDM) radial cell diameter across a ring;
the point at which the CSDM curve declined toward
zero was designated as the boundary (Fig. 6A, arrow).
Dendrologists and wood anatomists have traditionally
determined the EW–LW boundary by the ratio of cell wall
thickness to lumen diameter (Mork, 1928; Denne, 1989).
In Denne's (1989) two interpretations of Mork's (1928)
definition, using Formula 2 results in no latewood being
present in any of the Antarctic specimens (Figs. 6B, 13B).
Using Formula 1, latewood ranges from 0–10% in the
Permian wood (Fig. 6B) and 0–12% in the Triassic wood
(Fig. 13B). Comparing the method of Creber and
Chaloner (1984) with that of Mork's more commonly
used definition (as detailed in Denne, 1989) (Figs. 6, 13),
it is clear that the two techniques produce very different
results for percent latewood. For example, specimen
15,485 (Permian), would have 50–70 cells of latewood,
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
257
Fig. 13. Different methods of calculating EW–LW boundary using Triassic fossil wood (Fremouw Peak). A. CSDM method (Creber and Chaloner,
1984). The two graphs show results for two specimens (black and grey lines). EW–LW boundary = the point at which each line turns toward zero
(arrows). B. Denne's (1989) two methods. Thin grey line = 2a, Formula 1; thin black line = 2c, Formula 2. EW–LW boundary = the point at which
either thin line crosses the thick line (arrow) (see text for further explanation).
which equates to 21–30%, according to Creber and
Chaloner's method, but only 4–5 cells using Mork's
definition, or 1.7–2.1% (Formula 1 of Denne, 1989).
Creber and Chaloner used the CSDM method mainly to
determine EW–LW boundary, but they also correlated
ring types with certain environments. These ring types
(Creber and Chaloner, 1984; Types A–E, O) were based
on the trend line calculated from the radial cell diameter
only, and not the CSDM curve; the description in the text
(Creber and Chaloner, 1984, p. 371), however, does not
always match the graphical representation of the types
(pp. 372–373). Brison et al. (2001) provided drawings
and interpretations of Creber and Chaloner's (1984) ring
types but several of these (e.g., Types A, D, and E) are
defined differently from Creber and Chaloner (1984) and
are sometimes contradictory. For example, Type A of
Creber and Chaloner (1984, p. 371) was originally
described as having few latewood cells, although their
Fig. 5 illustrates a ring with few earlywood cells, and
∼69% latewood. Brison et al. (2001) describe Type A as
containing few earlywood cells. Types D and E of Creber
and Chaloner (1984) were based on the appearance of the
ring boundary (distinct vs. faint), whereas Brison et al.
(2001) differentiated these two types based on an EW–
LW transition that was distinct or faint. Much of the
difficulty in defining these ring types is due to the use of
the CSDM calculation, which includes only radial cell
diameter changes, to define the EW–LW boundary. By
Fig. 14. Calculation of evergreen vs. deciduousness of Antarctic woods
using method of Falcon-Lang (2000). Each point represents the difference
between the apex of the CSDM curve (see Figs. 6, 13) and the center of the
curve (percentage ‘skew’ of Falcon-Lang) for a single specimen.
258
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
using only this measurement, changes in wall thickness
and lumen size, two factors known to vary strongly with
environment, were not considered in these earlier
analyses. For these reasons and others discussed below,
we have calculated the EW–LW boundary in the
Antarctic fossil wood using Mork's definition (Formula
1 of Denne, 1989).
4.3. Deciduous or evergreen?
The interpretation of fossil leaf deposits as representing seasonally deciduous vs. evergreen plants, i.e. those
with leaves that remain attached for more than one
growing season, is important to paleoenvironmental
reconstructions and has been discussed by a number of
authors and analyzed from a variety of perspectives.
Spicer and Chapman (1990), based on examination of
high-latitude floras throughout the Phanerozoic, noted
that deciduous plants dominated very high latitudes
during times of global warmth, while evergreens were
more common during icehouse phases of Earth's
climate, such as today. In an attempt to develop a
more quantitative method of determining deciduousness
in fossils, Falcon-Lang (2000) proposed a method to
distinguish between evergreen and deciduous gymnosperms based on the CSDM equation. In the present
study, there were only three Permian and eight Triassic
samples that were sufficiently preserved to use FalconLang's method. The results span both the evergreen and
deciduous ranges (Fig. 14), i.e., above and below the
midpoint of the CSDM curve, respectively (= 0 in
Fig. 14). It is possible, though unlikely, that some of the
Triassic wood may represent a different taxon. In the
Permian peat from Skaar Ridge, Glossopteris is the only
woody gymnosperm present. Although Noeggerathiopsis leaves and associated wood have been
described from the Bainmedart Coal Measures of East
Antarctica (McLoughlin and Drinnan, 1996; Weaver
et al., 1997), this plant has not been found in the CTM,
so different systematic affinities cannot explain these
unusual results. There is a great deal of overlap in the
ranges for the various species examined by Falcon-Lang
(2000; see also Falcon-Lang, 2005a for results from a
single tree). For the reasons noted above, and because of
the wide variance in our results using this technique, we
believe it is problematic to extrapolate this method to
fossil woods.
Royer et al. (2003) performed growth chamber
experiments and developed a model that simulated
light conditions at 69°N and temperatures of the Late
Cretaceous–early Paleogene. This study concluded that
evergreen plants at this latitude had a slight advantage
over deciduous ones, based on above-ground carbon
budget only. More recent work suggests that the carbon
budget for evergreen and deciduous trees at high
latitudes is similar (Royer et al., 2005), but is distributed
differently throughout the year. Deciduous trees exhibited a flux of carbon uptake in late summer, which
helped to counterbalance the carbon loss from leaf
shedding. These authors note that the presence of highlatitude deciduous plants cannot be explained by carbon
budget alone and conclude that without modern analogs,
it is difficult to explain how apparently deciduous
fossil trees thrived, or to prove experimentally whether
deciduous or evergreen trees are more likely to be
present at these very high latitudes (Falcon-Lang, 2000;
Royer et al., 2003). Both carbon and nitrogen budgets
are often measured in extant forests, so these results may
be a limitation of the particular models used. Interpretation of deciduous vs. evergreen status has been based
traditionally on the presence of leaf mats and especially
the occurrence of large deposits of leaves in the ‘fall’
layers of varved deposits (Spicer, 1989). Glossopteris
leaves have been found in varved sediments (e.g.,
Plumstead, 1958; Gunn and Walcott, 1962; Retallack,
1980) and occur in mats in the permineralized peat from
the CTM. Spicer and Parrish (1986) and Spicer (1989)
found that leaves that are abscised in response to cold
tend to accumulate in mats due to a lower rate of decay.
Since the Antarctic material is permineralized it is also
possible to look for anatomical evidence of seasonal
deciduousness such as abscission layers. MeyerBerthaud et al. (1992, 1993) described a layer of
periderm beneath the leaf bases in Kykloxylon, the
young stem which bore Dicroidium leaves, in the
Triassic peat from the Fremouw Formation. This
periderm was interpreted as functioning similarly to an
abscission layer in that transport to the leaf would have
ceased after formation of these cells. Thus, the
anatomical and sedimentologic data suggest that both
the Glossopteris and Dicroidium ‘plants’ from Antarctica were seasonally deciduous. Anatomical evidence,
either in the leaf base or the stem itself, remains the most
exacting method for determination of deciduousness,
but unfortunately this level of preservation is rare.
4.4. Other fossil wood from Antarctica
Petrified or permineralized wood occurs at a number of
localities in Antarctica, both on the continent and the
Antarctic Peninsula. Fossil forests in growth position have
been described from Alexander Island (Jefferson, 1982)
on the Peninsula and from the central Transantarctic
Mountains. The Alexander Island forest is Early
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
Cretaceous whereas the forests from the CTM are Late
Permian (Mt. Achernar; Taylor et al., 1992) and Middle
Triassic (Gordon Valley; Cúneo et al., 2003). Glossopteris wood and logs are widespread in the Permian fluvial
coal measures of Antarctica. Well-preserved Early
Permian wood with growth rings from the Allan Hills,
southern Victoria Land, was analyzed by Francis et al.
(1993). The ring structure of both the Allan Hills wood
and the Late Permian wood from CTM presented in this
study appear very similar. Specimens from both localities
exhibit relatively large rings with a small proportion of
latewood. The Allan Hills wood exhibited many more
cells per ring (115, 141, and 194 cells/ring) than the Skaar
Ridge specimens (36–91 cells/ring), but ring widths are
similar due to differences in tracheid diameters. Tracheids
in wood from Skaar Ridge (mean 81 μm) are almost three
times the diameter of those in the Allan Hills wood (mean
30 μm). Although the Skaar Ridge site has been
reconstructed at a slightly higher paleolatitude, it is
difficult to explain why trees from the Early Permian
(Allan Hills) produced more cells each season than those
from the Late Permian since the paleoclimate of the Early
Permian was colder (e.g., Krull, 1999; Isbell et al., 2001;
Rees et al., 2002; Isbell et al., 2003a; Montañez et al.,
2007), unless there were local environmental factors that
contributed to the difference.
The wood described from a small standing fossil
forest in the Upper Permian on Mt. Achernar in the
CTM (Taylor et al., 1992) is similar in overall growth
ring anatomy to the material from Skaar Ridge, as it
contains only 1–3 cells of latewood per ring. The Mt.
Achernar wood, however, represents young trees, which
are known to grow very rapidly, so ring width is large
(mean 4.5 mm) and the number of cells per ring is
extremely large (∼ 350–400).
Well-preserved Dicroidium foliage and a standing
forest have also been described from the Middle Triassic
of Antarctica, from the upper part of the Fremouw
Formation in Gordon Valley, CTM (Cúneo et al., 2003).
This material is of equivalent age to the permineralized
peat from Fremouw Peak. Large stumps with up to 86
rings and ring widths of 0.92–2.54 mm were recorded
with each ring having very little latewood. Gabites (1985)
examined tree rings from silicified Middle Triassic wood
collected from fluvial deposits of the Lashly Formation,
Member B in the Allan Hills. Ring widths ranged from
0.49–2.12 mm and all were classified as complacent
based on mean sensitivity calculations (0.15–0.27).
Gabites (1985) also described wood from Member C of
the Lashly (Late Triassic). Ring widths for the two
specimens examined ranged from 0.32–0.57 mm and
both were classified as sensitive. Ring widths in the
259
present study are similar to those studied by Cúneo et al.
(2003) and Gabites (1985). Growth response of these
plants to the environment was very similar, even though
the climate in Antarctica was changing.
4.5. Permian–Triassic paleoclimate in Antarctica
From the Permian into the Triassic, Gondwana was in
transition from an icehouse to a greenhouse climate as
the Late Carboniferous–Early Permian glaciation waned
and ecosystems began to recover. These changes have
proved a challenge when correlating paleoclimate based
on physical models with that based on paleobotanical
data. Paleoclimate models for the Late Permian generate
temperatures at low latitudes that agree with paleobotanical evidence (e.g., Kiehl and Shields, 2005), but
high-latitude reconstructions show discrepancies between the models and paleobotanical data. Rees et al.
(2002) noted that their model for the Late Permian
(Wordian), which predicted a tundra environment at
high southern latitudes, did not match the paleobotanical
data even at 8X present-day CO2 levels. Although
Antarctica may have been a tundra environment in the
Late Permian, the wide geographical range of the woody
Glossopteris plant argues against this hypothesis. In the
earliest models, Antarctica was reconstructed as a
glacial–tundra environment (Crowley et al., 1987).
Yemane (1993) suggested that these high-latitude
climates could have been milder than model predictions
if continental interiors included either large lakes or
possibly interior seaways. Climate can also be ameliorated by the type of vegetation present, as illustrated in a
simulation model of high latitudes during the latest
Cretaceous (Otto-Bliesner and Upchurch, 1997;
Upchurch et al., 1998). By including a forest biome
rather than tundra in the model parameters, feedback
from albedo changes produced a much warmer climate
at high latitudes (+ 4.1–4.2 °C in the Northern
Hemisphere; + 3.4 °C in the Southern) and globally
(+ 2.2 °C). More recently, Kiehl and Shields (2005)
produced a paleoclimate model for the Permian that
incorporated a number of additional factors, such as a
fully coupled land and ocean system, as well as
paleogeographic features and high CO2. Their model
produced warmer temperatures at high latitudes than
any previous simulations, with a mean annual temperature at these latitudes of ∼ 10 °C. As paleoclimate
modeling becomes more sophisticated, resolution between the biological data and the model simulations is
converging.
Triassic climate reconstructions for the Antarctic
region based on physical models have generally agreed
260
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
with paleobotanical data, including the results of tree
ring analysis. During the Middle Triassic, the central
Transantarctic Mountains area has been reconstructed as
a warm-temperate climate capable of supporting trees
(Retallack et al., 1996). The Triassic was the beginning
of a continuing warm period in Earth's history and no
severe climate changes (i.e., icehouse conditions)
occurred throughout the Mesozoic. During the Triassic
the CTM were at slightly lower latitudes than during the
Permian (Powell and Li, 1994; Grunow, 1999). With the
formation of Pangea, continental interiors have been
modeled as arid (Crowley et al., 1989), yet tree growth
in the CTM suggests that these plants did not experience
extremes of either drought or cold.
There is little difference in the amount of wood
produced in trees from the Late Permian and the Middle
Triassic, and no difference in the structure of the rings
themselves. This is surprising given the large differences
in paleoclimate that are suggested not only by physical
models, but also by the greater diversity of plants in
Middle Triassic floras from Antarctica. Perhaps the
similarities in wood growth suggest that the Late Permian in Antarctica was warmer than any model has yet
predicted, although floral diversity does not support this
hypothesis. Isbell et al. (2003a,b) have hypothesized that
the model of a massive ice sheet centered on the CTM no
longer fits the more recent paleontological and sedimentary data (see also Babcock et al., 2002). Evidence
emerging from Australia also supports a reconstruction
of discrete glacial events with periods of interglacial or
periglacial conditions (Fielding et al., 2005; Montañez et
al., 2007); these studies, however, have concentrated on
the Late Carboniferous–Early Permian and not the Late
Permian. For many years, low floral diversity in the
Permian of Gondwana has been attributed to a cold
climate, and vice versa, with no independent data to
corroborate this theory. The glossopterids moved in
rapidly after the retreat of the ice sheet and perhaps
remained dominant throughout the Permian in Antarctica because once established, their densely borne, large
strap-shaped leaves shaded out competitors (Taylor,
1996). While these generalists were able to colonize
almost all environments in the Permian of Gondwana,
the series of climate perturbations that occurred around
the P–T boundary, including the continuously warming
climate, may have contributed to their extinction. As the
temperate glossopterid forests disappeared, more warmadapted seed ferns colonized Antarctica, perhaps
migrating from lower latitudes (Kerp et al., 2006),
resulting in a large increase in plant diversity through the
Triassic. Although the variety of plants growing during
the Middle Triassic of Antarctica is vastly different from
the Late Permian, the ring structure clearly indicates that
these plants were responding to their environments in a
similar way, providing evidence that other factors
besides temperature were limiting tree growth during
these time periods.
4.6. Interpretation of tree growth at high latitudes
In order to understand the unique structure of the
Antarctic tree rings and interpret its meaning, it is
important to examine modern tree growth and wood
production in the context of physiological ecology. Tree
rings from Antarctica all have a similar structure of
predominantly earlywood with a small amount of latewood produced at the end of the season. This structure,
coupled with the high paleolatitudes of these floras,
supports the hypothesis that woody plants in both the
Late Permian and Middle Triassic of Antarctica were
limited by light, rather than by a combination of
temperature and water availability as are woody plants
at high latitudes today.
In a series of classic papers, Larson (1960, 1962) and
subsequently others (e.g., Lindstrom, 1996) showed that
earlywood production in conifers is correlated with
elongation growth in the apical meristems and consequent high auxin levels, whereas latewood production is
correlated with cessation of terminal growth and the
resulting lower auxin concentrations in the cambium. In
temperate zones today, changes in day length during the
growing season are involved in triggering this change
(Larson, 1962). At very high latitudes, however, day
length during the summer is continuous. With no
substantial changes in day length, Larson's physiological model suggests that wood production at polar
latitudes should exhibit continuous production of
earlywood, as long as other factors are not limiting to
growth. In modern boreal woody plants, however,
temperature and water availability are limiting factors,
and woody plants do not grow above ∼ 72°N latitude
(lower in the southern hemisphere), so day length does
change during the growing season. In the higher latitude
forests of Antarctica, however, the ring structure demonstrates that these plants continued elongation growth
throughout the growing season, ceasing only at the
very end of the summer, at which time the few rows of
latewood cells (1–5) would have been produced. Using
Mork's traditional method to calculate EW–LW boundary, this type of growth is clearly evidenced in the
Antarctic woods—large amounts of earlywood followed by a very low percentage (∼ 0–12%) of latewood
before the ring boundary. Using the method outlined by
Creber and Chaloner (1984), however, it is difficult to
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
reconcile up to 59% latewood (for both Permian and
Triassic wood) with the physiology of tree growth in this
extreme environment. With almost half of the ring
latewood, elongation growth would have had to cease in
the middle of the growing season, yet there is no
evidence of cell wall thickening, as normally found in
latewood, until the very end of the season, i.e., the last
few cells in the ring. For these high-latitude woods, the
traditional calculation of the EW–LW boundary provides a more accurate interpretation of tracheid production and tree growth than the method utilized in
many previous studies of fossil tree rings.
Using Larson's (1962) model, the small amount of
latewood in Antarctic wood, and that seen in other highlatitude woods (e.g., Parrish and Spicer, 1988), can be
attributed to a growing season which ended only as a
result of inadequate light levels for photosynthesis
(Taylor et al., 1992; Francis et al., 1993), rather than by a
combination of water and temperature as in modern
boreal forests. At these paleolatitudes, this physiological
switch must have occurred as the sun, already low on the
horizon, moved rapidly below the horizon, at which
time photosynthesis could not occur, triggering leaf drop
and winter dormancy. Experimental studies and models
have shown that given temperatures above freezing,
trees are capable of surviving winter darkness (Read and
Francis, 1992; Beerling and Osborne, 2002; Royer et al.,
2003), although cold, dark winters are more easily
tolerated (Read and Francis, 1992).
5. Conclusions
Paleobotanical evidence, sedimentological analyses,
and physical models are increasingly resolving reconstructions of past climates. In spite of the advances in
these disciplines, problems remain in data interpretation.
As demonstrated by this analysis of Late Permian and
Middle Triassic tree rings from Antarctica, it is important
to include aspects of the growth and physiology of plants
when considering paleoclimate reconstructions. This is
especially critical when no modern analogue environment exists, as with these polar latitude fossil forests.
Research on modern wood has shown that the
proportion of earlywood to latewood in growth rings
is generally correlated with environmental factors. Thus,
the position of the EW–LW boundary is important in
extrapolating environmental parameters, such as growing season, for fossil woods. We have shown here,
however, that some previous studies have defined this
boundary incorrectly. Using Mork's (1928) and Denne's
(1989) standard technique to define the EW–LW boundary yields paleoenvironmental hypotheses which corre-
261
late well with observed wood anatomy. The occurrence
of anatomically preserved plants and wood samples
in permineralized peat from Antarctica offers an opportunity to examine both primary and secondary plant
growth and development within a climatic regime that
does not exist today. Parameters controlling highlatitude growth today (water availability and temperature) are different from those in periods of global warmth
(light levels), indicating that many factors, individually
or jointly, can control a tree's response to the environment. As more plants from these sites are reconstructed
and ideas about the composition of the community and
ecosystem refined, it should be possible to better understand not only deep-time climates, but also how
plants of the past responded to these unique environmental conditions.
Acknowledgements
Based upon work supported by the National Science
Foundation (OPP-0126230, OPP-0229877). We thank
past members of Antarctic field parties for field work
and helpful discussions, especially N.R. Cúneo, Museo
Paleontológico E. Fergulio, Trelew, Argentina; J. Isbell,
University of Wisconsin-Milwaukee; and T.N. Taylor,
University of Kansas. We also thank J. Ward and C.
Springer, University of Kansas, for interesting discussions on ecophysiology and two anonymous reviewers
for helpful comments and suggestions. Special thanks to
David Buchanan and Tim Culley, who collected the
trunk from McIntyre Promontory, with the assistance of
Helicopters New Zealand.
References
Ashworth, A.C., Cantrill, D.J., 2004. Neogene vegetation of the Meyer
Desert Formation (Sirius Group) Transantarctic Mountains,
Antarctica. Palaeogeography, Palaeoclimatology, Palaeoecology
213, 65–82.
Babcock, L.E., Isbell, J.L., Miller, M.F., Hasiotis, S.T., 2002. New
Late Paleozoic conchostracan (Crustacea: Branchiopoda) from the
Shackleton Glacier Area, Antarctica: age and paleoenvironmental
implications. Journal of Paleontology 76, 70–75.
Barrett, P.J., Elliot, D.J., 1973. Reconnaissance geologic map of the
Buckley Island Quadrangle, Transantarctic Mountains, Antarctica.
Antarctic Geologic Map (U.S. Geological Survey) A-3.
Beerling, D.J., Osborne, C.P., 2002. Physiological ecology of Mesozoic
polar forests in a high CO2 environment. Annals of Botany 89,
329–339.
Brison, A., Philippe, M., Thévenard, F., 2001. Are Mesozoic growth
rings climate induced? Paleobiology 27, 531–538.
Cantrill, D.J., Poole, I., 2005. Taxonomic turnover and abundance in
Cretaceous to Tertiary wood floras of Antarctica: implications for
changes in forest ecology. Palaeogeography, Palaeoclimatology,
Palaeoecology 215, 205–219.
262
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
Chapman, J.L., 1994. Distinguishing internal developmental characteristics from external palaeoenvironmental effects in fossil
wood. Review of Palaeobotany and Palynology 81, 19–32.
Creber, G.T., 1990. The south polar forest ecosystem. In: Taylor, T.N.,
Taylor, E.L. (Eds.), Antarctic Paleobiology: its Role in the Reconstruction of Gondwana. Springer-Verlag, New York, NY, pp. 37–41.
Creber, G.T., Chaloner, W.G., 1984. Influence of environmental
factors on the wood structure of living and fossil trees. Botanical
Review 50, 357–448.
Creber, G.T., Francis, J.E., 1987. Productivity in fossil forests. In:
Jacoby, G.C. (Ed.), Proceedings of the International Symposium
on Ecological Aspects of Tree-Ring Analysis. U.S. Department of
Energy, Washington, DC, pp. 319–326.
Crowley, T.J., Mengel, J.G., Short, D.A., 1987. Gondwanaland's
seasonal cycle. Nature 329, 803–807.
Crowley, T.J., Hyde, W.T., Short, D.A., 1989. Seasonal cycle variations
on the supercontinent of Pangaea. Geology 17, 457–460.
Cúneo, N.R., Isbell, J., Taylor, E.L., Taylor, T.N., 1993. The Glossopteris flora from Antarctica: taphonomy and paleoecology. 12
Congrès International de Géologie du Carbonifère-Permian,
Buenos Aires. Comptes Rendus, vol. 2, pp. 13–40.
Cúneo, N.R., Taylor, E.L., Taylor, T.N., Krings, M., 2003. In situ
fossil forest from the upper Fremouw Formation (Triassic) of
Antarctica: paleoenvironmental setting and paleoclimate analysis.
Palaeogeography, Palaeoclimatology, Palaeoecology 197,
239–261.
Del Fueyo, G.M., Taylor, E.L., Taylor, T.N., Cúneo, N.R., 1995.
Triassic wood from the Gordon Valley, central Transantarctic
Mountains, Antarctica. IAWA Journal 16, 111–126.
Delevoryas, T., Person, C.P., 1975. Mexiglossa varia gen. et sp. nov., a new
genus of glossopterid leaves from the Jurassic of Oaxaca, Mexico.
Palaeontographica Abteilung B Paläophytologie 154, 114–120.
Denne, M.P., 1989. Definition of latewood according to Mork (1928).
IAWA Bulletin 10, 59–62.
Edwards, D., 1990. Silurian–Devonian paleobotany: problems,
progress, and potential. In: Taylor, T.N., Taylor, E.L. (Eds.),
Antarctic Paleobiology: its Role in the Reconstruction of
Gondwana. Springer-Verlag, New York, pp. 89–101.
Falcon-Lang, H.J., 2000. A method to distinguish between woods
produced by evergreen and deciduous coniferopsids on the basis of
growth ring anatomy: a new palaeoecological tool. Palaeontology
43, 785–793.
Falcon-Lang, H.J., 2005a. Intra-tree variability in wood anatomy and
its implications for fossil wood systematics and palaeoclimatic
studies. Palaeontology 48, 171–183.
Falcon-Lang, H.J., 2005b. Global climate analysis of growth rings in
woods, and its implications for deep-time paleoclimate studies.
Paleobiology 31, 434–444.
Falcon-Lang, H.J., Cantrill, D.J., 2002. Terrestrial palaeoecology of
the Cretaceous (early Aptian) Cerro Negro Formation, South
Shetland Islands, Antarctica. A record of polar vegetation in a
volcanic arc environment. Palaios 17, 491–506.
Falcon-Lang, H.J., Cantrill, D.J., Nichols, G.J., 2001. Biodiversity and
terrestrial ecology of a mid-Cretaceous, high-latitude floodplain,
Alexander Island, Antarctica. Journal of the Geological Society
158, 709–724.
Farabee, M.J., Taylor, E.L., Taylor, T.N., 1990. Correlation of Permian
and Triassic palynomorph assemblages from the central Transantarctic Mountains, Antarctica. Review of Palaeobotany and
Palynology 65, 257–265.
Farabee, M.J., Taylor, E.L., Taylor, T.N., 1991. Late Permian
palynomorphs from the Buckley Formation in the central
Transantarctic Mountains. Review of Palaeobotany and Palynology 69, 353–368.
Fielding, C., Frank, T., Birgenheier, L., Thomas, S., Rygel, M., Jones,
A., 2005. Revised Permian glacial record of eastern Australia.
Abstracts with Programs - Geological Society of America 37 (7),
256.
Francis, J.E., 1986. Growth rings in Cretaceous and Tertiary wood
from Antarctica and their palaeoclimatic implications. Palaeontology 29, 665–684.
Francis, J.E., Hill, R.S., 1996. Fossil plants from the Pliocene Sirius
Group, Transantarctic Mountains: evidence for climate from
growth rings and fossil leaves. Palaios 11, 389–396.
Francis, J.E., Poole, I., 2002. Cretaceous and early Tertiary climates of
Antarctica: evidence from fossil wood. Palaeogeography, Palaeoclimatology, Palaeoecology 182, 47–64.
Francis, J.E., Woolfe, K.J., Arnot, M.J., Barrett, P.J., 1993. Permian
forests of Allan Hills, Antarctica: the palaeoclimate of Gondwanan
high latitudes. Special Papers in Palaeontology 49, 75–83.
Francis, J.E., Woolfe, K.J., Arnot, M.J., Barrett, P.J., 1994. Permian
climates of the southern margins of Pangea: evidence from fossil
wood in Antarctica. In: Embry, A.F., Beauchamp, B., Glass, D.J.
(Eds.), Pangea: Global Environments and Resources. Canadian
Society of Petroleum Geologists Memoir, vol. 17, pp. 275–282.
Fritts, H.C., 1976. Tree Rings and Climate. Academic Press, New York.
Fritz, W.J., 1980. Stumps transported and deposited upright by Mount
St., Helens mud flows. Geology 8, 586–588.
Gabites, H.I. 1985. Triassic paleoecology of the Lashly Formation,
Transantarctic Mountains, Antarctica. Unpublished Masters Thesis, Victoria University of Wellington, New Zealand, 148 pp.
Galfetti, T., Bucher, H., Brayard, A., Hochuli, P.A., Weissert, H.,
Guodun, K., Atudorei, V., Guex, J., 2007. Late Early Triassic
climate change: insights from carbonate carbon isotopes, sedimentary evolution and ammonoid paleobiogeography. Palaeogeography, Palaeoclimatology, Palaeoecology 243, 394–411.
Galtier, J.M., Phillips, T.L., 1999. The acetate peel technique. In: Jones,
T.P., Rowe, N.P. (Eds.), Fossil Plants and Spores: Modern
Techniques. Geological Society of London, London, UK, pp. 67–70.
Gastaldo, R.A., Adendorff, R., Bamford, M., Labandeira, C.C.,
Neveling, J., Sims, H., 2005. Taphonomic trends of macrofloral
assemblages across the Permian–Triassic boundary, Karoo Basin,
South Africa. Palaios 20, 479–497.
Gerrath, J.M., Matthes, U., Purich, M., Larson, D.W., 2005. Root
environmental effects on phi thickening production and root
morphology in three gymnosperms. Canadian Journal of Botany
83, 379–385.
Giddings, J.L., 1942. Dendrochronology in northern Alaska. University of Arizona Bulletin 12, 1–107.
Giddings, J.L., 1951. The forest edge at Norton Bay, Alaska. TreeRing Bulletin 18, 2–6.
Girardin, M., Berglund, E., Tardif, J.C., Monson, K., 2005. Radial
growth of tamarack (Larix laricina) in the Churchill area,
Manitoba, Canada, in relation to climate and larch sawfly
(Pristiphora erichsonii) herbivory. Arctic, Antarctic, and Alpine
Research 37, 206–217.
Gregory, R.A., Wilson, B.F., 1968. A comparison of cambial activity
of white spruce in Alaska and New England. Canadian Journal of
Botany 46, 733–734.
Grunow, A.M., 1999. Gondwana events and palaeogeography: a
palaeomagnetic review. Journal of African Earth Sciences 28, 53–69.
Gunn, B.M., Walcott, R.I., 1962. The geology of the Mt. Markham
region, Ross dependency, Antarctica. New Zealand Journal of
Geology and Geophysics 5, 407–426.
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
Isbell, J.L., Miller, M.F., Babcock, L.E., Hasiotis, S.T., 2001. Icemarginal environment and ecosystem prior to initial advance of the
late Palaeozoic ice sheet in the Mount Butters area of the central
Transantarctic Mountains, Antarctica. Sedimentology 48,
953–970.
Isbell, J.L., Lenaker, P.A., Askin, R.A., Miller, M.F., Babcock, L.E.,
2003a. Reevaluation of the timing and extent of late Paleozoic
glaciation in Gondwana: role of the Transantarctic Mountains.
Geology 31, 977–980.
Isbell, J.L., Miller, M.F., Wolfe, K.L., Lenaker, P.A., 2003b. Timing of
late Paleozoic glaciation in Gondwana: was glaciation responsible
for the development of northern hemisphere cyclothems? Special
Paper - Geological Society of America 370, 5–23.
Jefferson, T.H., 1982. Fossil forests from the Lower Cretaceous of
Alexander Island, Antarctica. Palaeontology 25, 681–708.
Kerp, H., Hamad, A.A., Vörding, B., Bandel, K., 2006. Typical
Triassic Gondwanan floral elements in the Upper Permian of the
paleotropics. Geology 34, 265–268.
Kidder, D.L., Worsley, T.R., 2004. Causes and consequences of
extreme Permo-Triassic warming to globally equable climate and
relation to the Permo-Triassic extinction and recovery. Palaeogeography, Palaeoclimatology, Palaeoecology 203, 207–237.
Kiehl, J.T., Shields, C.A., 2005. Climate simulation of the latest
Permian: implications for mass extinction. Geology 33, 757–760.
Krull, E.S., 1999. Permian palsa mires as paleoenvironmental proxies.
Palaios 14, 530–544.
Larson, P.R., 1960. A physiological consideration of the springwood–
summerwood transition in red pine. Forest Science 6, 110–122.
Larson, P.R., 1962. The indirect effect of photoperiod on tracheid
diameter in Pinus resinosa. American Journal of Botany 49,
132–137.
Larson, P.R., Kretschmann, D.E., Clark III, A., Isebrands, J.G., 2001.
Formation and properties of juvenile wood in southern pines: a
synopsis. USDA Forest Products Laboratory General Technical
Report FPL-GTR-129, Madison, WI. 42 pp.
Lindstrom, H., 1996. Basic density of Norway spruce. Part II. Predicted
by stem taper, mean growth ring width, and factors related to crown
development. Wood and Fiber Science 28, 240–251.
Maheshwari, H.K., Bajpai, U., 1996. Ultrastructure of the “cuticular
membrane” in two Late Triassic corystospermaceous taxa from
India. The Palaeobotanist 45, 41–49.
McLoughlin, S., 2001. The breakup history of Gondwana and its
impact on pre-Cenozoic floristic provincialism. Australian Journal
of Botany 49, 271–300.
McLoughlin, S., Drinnan, A.N., 1996. Anatomically preserved
Permian Noeggerathiopsis leaves from East Antarctica. Review
of Palaeobotany and Palynology 92, 207–227.
McLoughlin, S., Lindstrom, S., Drinnan, A.N., 1997. Gondwanan
floristic and sedimentological trends during the Permian–Triassic
transition: new evidence from the Amery Group, northern
Prince Charles Mountains, East Antarctica. Antarctic Science 9,
281–298.
McManus, H.A., Taylor, E.L., Taylor, T.N., Collinson, J.W., 2002. A
petrified Glossopteris flora from Collinson Ridge, central
Transantarctic Mountains: Late Permian or Early Triassic? Review
of Palaeobotany and Palynology 120, 233–246.
Meyer-Berthaud, B., Taylor, E.L., Taylor, T.N., 1992. Reconstructing
the Gondwana seed fern Dicroidium: evidence from the Triassic of
Antarctica. Géobios 25, 341–344.
Meyer-Berthaud, B., Taylor, T.N., Taylor, E.L., 1993. Petrified stems
bearing Dicroidium leaves from the Triassic of Antarctica.
Palaeontology 36, 337–356.
263
Millay, M.A., Taylor, T.N., Taylor, E.L., 1987. Phi thickenings in fossil
seed plants from Antarctica. IAWA Bulletin N.S. 8, 191–201.
Montañez, I.P., Tabor, N.J., Niemeier, D., DiMichele, W.A., Frank, T.D.,
Fielding, C.R., Isbell, J.L., Birgenheier, L.P., Rygel, M.C., 2007.
CO2-forced climate and vegetation instability during Late Paleozoic
deglaciation. Science 315, 87–91.
Mork, E., 1928. Die Qualität des Fichtenholzes unter besonderer
Rücksichtnahme auf Schleif-und Papierholz. Der Papier-Fabrikant
26, 741–747.
Neish, P.G., Drinnan, A.N., Cantrill, D.J., 1993. Structure and ontogeny
of Vertebraria from silicified Permian sediments in East Antarctica.
Review of Palaeobotany and Palynology 79, 221–244.
Oswalt, W.H., 1950. Spruce borings from the Lower Yukon River,
Alaska. Tree-Ring Bulletin 16, 26–30.
Oswalt, W.H., 1952. Spruce samples from the Copper River Drainage,
Alaska. Tree-Ring Bulletin 19, 5–10.
Oswalt, W.H., 1960. The growing season of Alaskan spruce. TreeRing Bulletin 23, 3–9.
Otto-Bliesner, B.L., Upchurch, G.R., 1997. Vegetation-induced
warming of high-latitude regions during the Late Cretaceous
period. Nature 385, 804–807.
Parrish, J.T., Spicer, R.A., 1988. Middle Cretaceous wood from the
Nanushuk Group, central North Slope, Alaska. Palaeontology 31,
19–34.
Pigg, K.B., Taylor, T.N., 1993. Anatomically preserved Glossopteris
stems with attached leaves from the central Transantarctic
Mountains, Antarctica. American Journal of Botany 80, 500–516.
Pires, E.F., Guerra-Sommer, M., Scherer, C.M.S., 2005. Late Triassic
climate in southernmost Paraná Basin (Brazil): evidence from
dendrochronological data. Journal of South American Earth
Sciences 18, 213–221.
Plumstead, E.P., 1958. The habit of growth of Glossopteridae.
Transactions of the Geological Society of South Africa 61, 81–96.
Poole, I., Cantrill, D.J., 2006. Cretaceous and Cenozoic vegetation of
Antarctica integrating the fossil wood record. In: Francis, J.E.,
Pirrie, D., Crame, J.A. (Eds.), Cretaceous–Tertiary High-Latitude
Palaeoenvironments, James Ross Basin, Antarctica. Geological
Society of London, Special Publication, vol. 258, pp. 63–81.
Powell, C.M., Li, Z.X., 1994. Reconstruction of the Panthalassan
margin of Gondwanaland. In: Veevers, J.J., Powell, C.M. (Eds.),
Permian–Triassic Pangean Basins and the Foldbelts Along the
Panthalassan Margin of Gondwanaland. Geological Society of
America Memoir, vol. 184, Boulder, CO, pp. 5–9.
Rasband, W.S., 1997–2004. ImageJ. National Institutes of Health,
Bethesda, Maryland, USA. http://rsb.info.nih.gov/ij/.
Read, J., Francis, J., 1992. Responses of some Southern Hemisphere
tree species to a prolonged dark period and their implications for
high-latitude Cretaceous and Tertiary floras. Palaeogeography,
Palaeoclimatology, Palaeoecology 99, 271–290.
Rees, P.M., 2002. Land-plant diversity and the end-Permian mass
extinction. Geology 30, 827–830.
Rees, P.M., Ziegler, A.M., Gibbs, M.T., Kutzbach, J.E., Behling, P.J.,
Rowley, D.B., 2002. Permian phytogeographic patterns and
climate data/model comparisons. Journal of Geology 110, 1–31.
Retallack, G.J., 1980. Late Carboniferous to Middle Triassic
megafossil floras from the Sydney Basin. In: Herbert, C., Helby,
R.J. (Eds.), A Guide to the Sydney Basin. Geological Survey of
New South Wales Bulletin, NSW, pp. 384–430.
Retallack, G.J., 2005. Early Triassic fossil plants from the Transantarctic
Mountains. Antarctic Journal of the United States 33, 272–277.
Retallack, G.J., Krull, E.S., Robinson, S.E., 1996. Permian and Triassic
paleosols and paleoenvironments of the central Transantarctic
264
E.L. Taylor, P.E. Ryberg / Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 246–264
Mountains, Antarctica. Antarctic Journal of the United States 31 (2),
29–32.
Royer, D.L., Osborne, C.P., Beerling, D.J., 2003. Carbon loss by
deciduous trees in a CO2-rich ancient polar environment. Nature
424, 60–62.
Royer, D.L., Osborne, C.P., Beerling, D.J., 2005. Contrasting seasonal
patterns of carbon gain in evergreen and deciduous trees of ancient
polar forests. Paleobiology 31, 141–150.
Schweingruber, F.H., 1988. Tree Rings: Basics and Applications of
Dendrochronology. Kluwer, Dordrecht. 276 pp.
Scotese, C.R., 2002. PALEOMAP Project. http://www.scotese.com,
(PALEOMAP website).
Spicer, R.A., 1989. The formation and interpretation of plant fossil
assemblages. Advances in Botanical Research 16, 96–191.
Spicer, R.A., Chapman, J.L., 1990. Climate change and the evolution
of high-latitude terrestrial vegetation and floras. Trends in Ecology
and Evolution 5, 279–284.
Spicer, R.A., Parrish, J.T., 1986. Paleobotanical evidence for cool
North Polar climates in middle Cretaceous (Albian–Cenomanian)
time. Geology 14, 703–706.
Taylor, E.L., 1996. Enigmatic gymnosperms? Structurally preserved
Permian and Triassic seed ferns from Antarctica. Review of
Palaeobotany and Palynology 90, 303–318.
Taylor, T.N., Archangelsky, S., 1985. The Cretaceous pteridosperms
Ruflorinia and Ktalenia and implications on cupule and carpel
evolution. American Journal of Botany 72, 1842–1853.
Taylor, E.L., Putz, M.K., 1993. Wood anatomy and tree ring structure
in Larix sibirica: an analogue for high latitude fossil forest growth.
American Journal of Botany 80 (6, Supplement), 94.
Taylor, E.L., Taylor, T.N., 1990. Structurally preserved Permian and
Triassic floras from Antarctica. In: Taylor, T.N., Taylor, E.L.
(Eds.), Antarctic Paleobiology. Springer-Verlag, New York, NW,
pp. 149–163.
Taylor, E.L., Taylor, T.N., Collinson, J.W., 1989. Depositional setting
and paleobotany of Permian and Triassic permineralized peat from
the central Transantarctic Mountains, Antarctica. International
Journal of Coal Geology 12, 657–679.
Taylor, E.L., Taylor, T.N., Cúneo, N.R., 1992. The present is not the
key to the past: a polar forest from the Permian of Antarctica.
Science 257, 1675–1677.
Taylor, E.L., Taylor, T.N., Isbell, J.L., 1997. Evidence of Permian
forests from the Shackleton Glacier area, Antarctica. American
Journal of Botany 84 (6, suppl.), 143.
Taylor, E.L., Taylor, T.N., Cùneo, N.R., 2000. Permian and Triassic
high latitude paleoclimates: evidence from fossil biotas. In: Huber,
B.T., MacLeod, K.G., Wing, S.L. (Eds.), Warm Climates in Earth
History. Cambridge Univ. Press, Cambridge, UK, pp. 321–350.
Thomas, H.H., 1933. On some pteridospermous plants for the
Mesozoic of South Africa. Philosophical Transactions of the
Royal Society of London Series. B 222, 193–265.
Upchurch Jr., G.R., Otto-Bliesner, B.L., Scotese, C., 1998. Vegetation–
atmosphere interactions and their role in global warming during the
latest Cretaceous. Philosophical Transactions of the Royal Society of
London. Series B, Biological Sciences 353, 97–112.
Weaver, L., McLoughlin, S., Drinnan, A.N., 1997. Fossil woods from
the Upper Permian Bainmedart Coal Measures, northern Prince
Charles Mountains, East Antarctica. Journal of Australian Geology
and Geophysics 16, 655–676.
Woods, A.D., 2005. Paleoceanographic and paleoclimatic context of
Early Triassic time. Comptes Rendus Palevol 4, 395–404.
Yemane, K., 1993. Contribution of Late Permian palaeogeography in
maintaining a temperate climate in Gondwana. Nature 361, 51–54.
RELATED PAPERS
Palaeogeography, Palaeoclimatology, Palaeoecology vol 363–364
Animal–plant interactions in a Middle Permian permineralised peat of the Bainmedart Coal Measures, Prince Charles Mountains, Antarctica2012 •
2000 •
Revista de la Asociación …
El Bosque Darwin en Agua de la Zorra: El primer bosque in situ descubierto en América del Sur por Darwin en 18352009 •
Journal of South American Earth Sciences
Late Triassic climate in southernmost Parana Basin (Brazil): evidence from dendrochronological data2005 •
Palaeogeography, Palaeoclimatology, Palaeoecology
The relationship between leaf longevity and growth ring markedness in modern conifer woods and its implications for palaeoclimatic studies2000 •
Paleobiology
Global climate analysis of growth rings in woods, and its implications for deep-time paleoclimate studies2005 •
Review of Palaeobotany and Palynology
Permineralized lycopsid from the Permian of Antarctica2011 •
American Journal of …
Development and ecological implications of dormant buds in the high-Paleolaltitude Triassic sphenophyte Spaciinodum (Equisetaceae)2008 •
Journal of South American Earth Sciences
Early Cretaceous coniferous woods from a paleoerg (Paraná Basin, Brazil2011 •
Geological Society, London, Special Publications
Palaeoclimatic implications of Middle Jurassic (Bajocian) coniferous wood from the Neuquen Basin, west-central Argentina2005 •
Alcheringa: An Australasian Journal of …
Elchaxylon, a new corystosperm based on permineralized stems from the Late Triassic of Argentina2007 •
Palaeontology
Intra‐tree variability in wood anatomy and its implications for fossil wood systematics and palaeoclimatic studies2005 •
Australian Journal of Earth Sciences
Landscape ecological shift at the Permian–Triassic boundary in Antarctica1999 •
Palaeogeography, Palaeoclimatology, Palaeoecology
Pole 1999 Structure of a near-polar latitude forest from the New Zealand Jurassic1999 •
2009 •
Palaeogeography, Palaeoclimatology, Palaeoecology
Upper Cretaceous–Paleocene conifer woods from Big Bend National Park, Texas2005 •
Global and Planetary Change
Return to Coalsack Bluff and the Permian-Triassic boundary in Antarctica2007 •
2015 •
Antarctic Journal of the United States
Permian and Triassic driftwood from the Allan Hills, Antarctica1995 •
Palaeogeography, Palaeoclimatology, Palaeoecology
Permian phytogeography in Gondwana1996 •
Australian Journal of Botany
The breakup history of Gondwana and its impact on pre-Cenozoic floristic provincialism2001 •