mariuSz lamentowicz1, w.o. van der knaap2, J.F.n. van leeuwen2, S. hanGartner3, e.a.d. mitchell4,5,6, t. GoSlar7,8, w. tinner2 and c. kamenik9
1
Department of Biogeography and Palaeoecology, Adam Mickiewicz University, Poznań, Poland; mariuszl@amu.edu.pl
2
Institute of Plant Sciences and Oeschger Centre for Climate Change Research, University of Bern, Switzerland; 3Physics Institute Climate and Environmental Physics, and Oeschger Centre for Climate Change Research, University of Bern, Switzerland; 4Swiss Federal Research Institute, Wetlands Research Group, Lausanne, Switzerland; 5École Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Ecological Systems, Switzerland;
6
Laboratory of Soil Biology, Institute of Biology, University of Neuchâtel, Switzerland; 7Faculty of Physics, Adam Mickiewicz University, Poznań,
Poland; 8Poznań Radiocarbon Laboratory, Foundation of the Adam Mickiewicz University, Poznań, Poland; 9Institute of Geography, and Oeschger
Centre for Climate Change Research, University of Bern, Switzerland
Science Highlights: Peatlands
A multi-proxy high-resolution approach to
reconstructing past environmental change from an
Alpine peat archive
High-resolution multiproxy studies on alpine peatlands reveal how environmental changes (including human
impact) have influenced the developmental history of these unusual ecosystems. Here we summarize results
of new paleoclimate reconstructions based on calibration and validation with the instrumental climate record.
Global warming is dramatically changing
mountain ecosystems; glaciers are shrinking and current snow conditions differ
considerably from those that existed 50
years ago (Laternser and Schneebeli, 2003;
Wipf et al., 2009). Among various types of
mountain ecosystems, peatlands stand
out because of their ecologically and biogeographically unique flora and fauna,
and their role as carbon pools and sinks.
Peatlands are also highly sensitive to human impact and climatic change. Because
peatlands accumulate records of their developmental history, including responses
to climate changes, land-use and human
impact, they represent a valuable source
of information on past and ongoing global changes (Charman, 2002). However, paleoecological data on peatland development in alpine regions are scarce.
Most modern high-resolution multiproxy studies of mountainous regions
have been based on lake sediments (e.g.,
Ammann, 1986; Ammann et al., 2000, van
der Knaap et al., 2000). However, in the
past decade, peatlands have been used
to address specific questions that demand
high spatial or temporal resolution. Small
peatlands have been used to gain records
of Holocene and Late-Glacial stand-scale
dynamics (where “stand” is defined as
an area of sufficient homogeneity to be
regarded as a single unit; Dahlgren and
Turner, 2010) (van der Knaap et al., 2003;
Genries et al., 2009; Stahli et al., 2006). Such
paleoenvironmental records may differ
from more regional signals, such as those
recorded in lacustrine sequences. For instance, Hofstetter et al. (2006) analyzed a
small peatland (0.05 ha) in the Southern
Alps and suggested that important tree
species (e.g., Abies alba, Castanea sativa)
were present locally millennia before they
could be unambiguously recorded in the
larger (5-20 ha) lake archives.
Figure 1: A) The Alpine landscape where the peatland is situated; B) Typical vegetation with Sphagnum fuscum
hummocks surrounded by brown mosses and vascular plants, C) Location of Mauntschas Mire (red star) in the
Engadine region, Switzerland. The meteorological station Sils Maria is indicated by the blue square (Map modified
from Lamentowicz et al., 2010).
It is currently not clear which factors have
the strongest influence on peatland development. For example, the hydrology
of alpine peatlands is controlled not only
by summer precipitation but also by the
amount and duration of snow cover. Addressing these issues requires integrated
studies of modern peatlands and their history.
Multiple proxies in peat deposits can
be studied at near-annual resolution, at
least for recent centuries, but such studies
are still very rare. Although time-consuming, they provide a temporally precise continuous paleoecological record. Moreover,
peat archives from the last 150 years offer
an opportunity to correlate reconstructed
time series with instrumental meteorological data and other historical information.
We use a high-resolution time series to validate transfer function-based quantitative
reconstructions against measured climate
variables (temperature and precipitation).
Case study – Mauntschas Mire
Within the framework of the EU project
MILLENNIUM
(http://geography.swan.
ac.uk/millennium), we obtained a highresolution (near-annual) multi-proxy record from Mauntschas Mire, a subalpine
peatland (1818 m asl) at the bottom of the
Upper Engadin Valley in the southeastern
Swiss Alps (Fig. 1). The site recorded local hydrological changes that can be related to local precipitation/temperature
changes since AD 1000. The aim of this
multi-proxy study was to reconstruct climate and other environmental changes
of the last millennium using the highest
possible sampling resolution, close to annual whenever possible. To achieve this
aim, the core was divided into 2 mm slices
with the Damocles device (Joosten and
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PAGES news • Vol 18 • No 1 • April 2010
Science Highlights: Peatlands
chum are highly correlated and lead to the
conclusion that δ18O fractionation in both
moss genera and in different parts of the
plant occurs in a similar way. A multi-proxy
analysis of δ18O and testate amoebae
might reveal underlying hydrological processes in Mauntschas Mire (Lamentowicz
et al., in prep.).
Pollen based calibration-in-time
Figure 2: Age-depth model of the peat profile Mauntschas MA2, calculated with a free-shape modeling algorithm
with information on relative changes of peat-accumulation rate. Open silhouettes show results of calibration of
individual 14C dates, treated as independent of one another. The best-fit age-depth model is shown with a solid
line, while uncertainty of the model is illustrated with orange silhouettes (modified from Goslar et al., 2009).
De Klerk, 2007). High-resolution radiocarbon dating combined with advanced
age-depth modeling (Goslar et al., 2009)
and the study of plant macrofossils, pollen, stable isotopes and testate amoebae
enabled precise paleoenvironmental reconstructions.
1950 (ca. 660 mm in peat profile MA2), and
is less than ±50 years between AD 1000–
1550. Adding constraints derived from
pollen concentration distinctly improved
precision of the age–depth model, without any deterioration in the fit of 14C dates.
Hydrological reconstruction
Chronology – age-depth
modeling
An age–depth model, based on 29 radiocarbon dates spanning the last 1.3 ka, was
constructed (Fig. 2) using the algorithm of
free-shape modeling (Goslar et al., 2009).
This algorithm searched for a reasonable
compromise between fit of 14C dates to
the radiocarbon calibration curve, general smoothness of the age–depth line,
and similarity of relative changes in the
modeled sediment-accumulation rates
to those suggested by independent data.
The complicated shape of the age-depth
curve was indicated by parallel fluctuations in concentrations of most pollen
taxa, supported in the upper part of the
profile by the record of anthropogenic
spheroidal carbonaceous particles, and
in some levels also by the 14C dates themselves.
Uncertainty in the obtained model
was assessed using Monte Carlo simulations. This uncertainty is 1–2 years in the
post-bomb period (AD 1950–2004), does
not exceed ±30 years between AD 1550–
Subfossil testate amoebae, stable oxygen
isotopes, and pollen were used to reconstruct the hydrological history of the last
1 ka. Using a testate-amoeba training set
from peatlands in the same valley (Lamentowicz et al., 2010) we reconstructed
depth to the water table in Mauntschas
Mire. Comparison of reconstructions
with instrumental records from AD 1864
showed that decreasing water tables
were correlated with increasing temperatures (Lamentowicz et al., 2010). However,
analyses also showed a significant positive
correlation between winter precipitation
and mire wetness. Despite the apparently
complex causes for the water table fluctuations, in the wider time frame we observed a clear hydrological signal related
to documented climate changes.
The stable oxygen isotope chronology (δ18O) from Sphagnum (moss) stems
shares similarities with the water-table reconstruction both before and during the
instrumental period, with an anti-correlated phase at the end of the 19th century.
The δ18O data from Sphagnum and Polytri-
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PAGES news • Vol 18 • No 1 • April 2010
Quantitative pollen-based reconstructions are challenging in mountainous
regions because of vertical pollen transport across vegetation boundaries. Thus,
instead of applying the usual calibrationin-space approach, selected pollen taxa
were calibrated in time (AD 1954 – 2002)
on temperature measured at the nearby
meteorological station Sils Maria. This approach was based on the rationale that
local factors controlling vertical pollen
transport (e.g., slope, dominant winds, exposure) were constant at a site that is used
for calibration and reconstruction alike.
Calibration in time resulted in a cross-validated (jackknifed) root mean square error
of prediction of 0.23°C for mean April–November air temperature (Kamenik et al.,
2009) (Fig. 3). Potential anthropogenic effects, such as de- or re-forestation, were
removed prior to calibration. This "calibration-in-time", which was carefully tested
against measured temperature, was possible only because two crucial pre-conditions were met: near-annual to quasiannual sampling resolution and excellent
dating (see above) provided by the 14C
bomb peak and spheroidal carbonaceous
particles. Independent validation using
the instrumental record revealed that pollen picked up decadal- to centennial-scale
climate change during this period. Still,
pollen-based reconstructions might be
challenged by non-climatic factors, such
as pre-industrial deforestation and fire.
Other studies from Alpine
peatlands
Investigations of small peatlands can also
help address important nature-conservation and forest-management issues. For
instance, an ongoing interdisciplinary
project is providing a scientific basis for
natural and sustainable forest management in the Italian part of Switzerland
(Valsecchi et al., 2010). In the northern
Alps, a recent multi-proxy study investigating peatland development and its
effect on landscape dynamics and tufa
formation (Wehrli et al., 2010), showed
that wetlands can reflect environmental
changes at extra-local scales.
Alpine peatlands are underused as a
source of paleoenvironmental informa-
Science Highlights: Peatlands
from Mauntschas to determine if these
patterns can also be observed elsewhere,
and 2) manipulative experiments to assess the relative influences of temperature, precipitation and water table depth
on testate amoeba communities and the
Sphagnum δ18O isotopic signal. Such combined studies will help understand which
factors most strongly control the development of alpine peatlands, how these peatlands can be fully exploited for inferring
paleoclimatic and environmental signals,
and how they may respond to ongoing
and future climate changes.
References
Figure 3: Confidence bands (95%) of detrended (upper panel) and non-detrended (lower panel) pollen-based
warm-season temperature reconstructions (red) versus measured temperature (solid black line) during the
instrumental period. Pollen picked up long-term (at least decadal-scale) temperature changes (e.g., 1900-1950).
Time series were detrended to reduce the effects of human impact. Calibration period (AD 1954 onwards) and
verification period (pre-AD 1954) are delineated by a dashed vertical line (modified from Kamenik et al. 2009).
tion. There is potential for scientists to use
peatlands in mountain regions as archives
of past climate change and landscape
transformation. However, peatland ecology and the relationship between climate
and peatland development needs to be
better understood.
Perspectives
The comparison of testate amoeba-inferred water table depth, δ18O data from
Sphagnum stems, and instrumental climatic data revealed some interesting correlations. We now need 1) more high-resolution multi-proxy studies similar to that
Goslar, T., Van der Knaap, W.O., Kamenik, C. and Van Leeuwen, J.F.N.,
2009: Free-shape 14C age–depth modelling of an intensively
dated modern peat profile, Journal of Quaternary Science, 24:
481-499.
Kamenik, C., Van der Knaap, W.O., Van Leeuwen, J.F.N. and Goslar, T.,
2009: Pollen/climate calibration based on a near-annual peat
sequence from the Swiss Alps, Journal of Quaternary Science,
24: 529–546.
Lamentowicz, M., Van der Knaap, P., Lamentowicz, Ł., Van Leeuwen,
J.F.N., Mitchell, E. A.D., Goslar, T. and Kamenik, C., 2010: A nearannual palaeohydrological study based on testate amoebae from
an Alpine mire: surface wetness and the role of climate during
the instrumental period, Journal of Quaternary Science, in press
DOI 10.1002/jqs.1295.
Mitchell, E.A.D., van der Knaap, W.O., van Leeuwen, J.F.N., Buttler, A.,
Warner, B.G. and Gobat, J.M., 2001: The palaeoecological history
of the Praz-Rodet bog (Swiss Jura) based on pollen, plant macrofossils and testate amoebae (Protozoa), The Holocene, 11: 65-80.
Wipf, S., Stoeckli, V. and Bebi, P., 2009: Winter climate change in alpine
tundra: plant responses to changes in snow depth and snowmelt
timing, Climatic Change, 94: 105-121.
For full references please consult:
http://www.pages-igbp.org/products/newsletters/ref2010_1.html
Stable isotopes and organic geochemistry in peat:
Tools to investigate past hydrology, temperature and
biogeochemistry
erin l. mcclymont1, e. pendall2 and J. nicholS3
1
School of Geography, Politics and Sociology, Newcastle University, UK; erin.mcclymont@ncl.ac.uk
2
Department of Botany and Program in Ecology, University of Wyoming, USA; 3NASA Goddard Institute for Space Studies, New York, USA
Characterizing the stable isotope and biomarker geochemistry of peat cores enables reconstruction of key
climatic and environmental variables in the past, including temperature, hydrology and the cycling of carbon.
Proxy targets and the value of
geochemistry
Peatlands are valuable archives of terrestrial environmental change due to their
sensitivity to the hydrological regime and
the excellent preservation of organic matter. Peat geochemistry reflects the composition of the original peat-forming plant
assemblage (which is itself dependent
on air temperature and hydrology), and
the subsequent transformation of that organic matter in the aerobic surface layer
(the acrotelm) and the anaerobic catotelm
(below the water table). Changes to air
temperatures and water table depth are
thus reflected in peat via changes to both
organic matter input and its subsequent
degradation (Fig. 1). Precipitation and
evaporation cause isotopic fractionation
of hydrogen (δD) and oxygen (δ18O), so
that the isotopic composition of the meteoric water used by peatland plants reflects
a combination of precipitation source and
peatland hydrology (Daley et al., in press).
Stable carbon isotopes (δ13C) give important information on carbon pathways,
including fractionation during photosynthesis (White et al., 1994; Williams and
Flanagan, 1996), and the recycling of organic matter and consumption of CO2 and
methane by microbial activity (Pancost et
al., 2000).
Humic acid formation during degradation
of plant material (humification) is a proxy
for peatland wetness (Yeloff and Mauquoy, 2006). Total carbon and nitrogen
contents also indicate wetness (McClymont et al., 2008), since drier conditions
cause the plant remains to spend a longer
time in the acrotelm, where degradation
preferentially releases nitrogen over carbon (Kuhry and Vitt, 1996). However, isolating whether changes to biomass and/or
peatland hydrology drive the humification
or bulk geochemistry signals recorded in
peat cores makes environmental interpretations of such records difficult (Yeloff
and Mauquoy, 2006). Here, we discuss the
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M. Lamentowicz, W.O. van der Knaap, J.F.N. van Leeuwen, S. Hangartner, E.A.D.
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Quaternary Science, 24: 481-499.
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Holocene vegetation history in the Insubrian Southern Alps - New indications from a
small-scale site, Vegetation History and Archaeobotany, 15: 87-98.
Joosten, H. and De Klerk, P., 2007: DAMOCLES: a DAshing MOnolith Cutter for fine
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Kamenik, C., Van der Knaap, W.O., Van Leeuwen, J.F.N. and Goslar, T., 2009:
Pollen/climate calibration based on a near-annual peat sequence from the Swiss Alps,
Journal of Quaternary Science, 24: 529–546.
Lamentowicz, M., Van der Knaap, P., Lamentowicz, Ł., Van Leeuwen, J.F.N., Mitchell, E.
A.D., Goslar, T. and Kamenik, C., 2010: A near-annual palaeohydrological study based
on testate amoebae from an Alpine mire: surface wetness and the role of climate during
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Lamentowicz, M., Van der Knaap, W.O., van Leeuwen, J.F.N., Goslar, E.D.M., Mitchell,
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palaeoenvironmental study from an Alpine mire. in prep.
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(1931-99), International Journal of Climatology, 23: 733-750.
Stahli, M., Finsinger, W., Tinner, W. and Allgower, B., 2006: Wildfire history and fire
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and plant macrofossils, The Holocene, 16: 805-817.
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Valley (central Switzerland), The Holocene, in press.
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