Peat as an organic record

Peat as an organic record

Peat Society Clip

Miguel Ángel Mateo Mínguez - Centro de Estudios Avanzados de Blanes - CSIC

Máster Universitario en Cambio GlobalDoctoradoPrograma Oficial de Posgrado adaptado al EEES

http://peatsociety.org/

PeatDescription

• Peat accumulates at a rate of about 0.5 - 1 mm per year (or 5-10 mover 10,000 years) with strong local variations. Peat can be formed from mosses, lichens, sedges, grasses, shrubs (heather) or trees. In northern regions, mosses are the main peat-forming plants while trees are the main ones in the tropics. Most peatlands that exist today formed in the last 15,000 years since the last Ice Age.

• Peat consists of accumulated dead plant material of which at least 50% is carbon.

• Water saturation means that plant remains decompose slowly and form peat

Peat moss Sphagnum flexuosum

Lichen in peat

Sphagnum spp. Moss peat with sedges of Carex spp.


PeatDistribution of the record• Peat has been forming in the

planet during the last 360 Million yr and nowadays holds 550 Gt of carbon (1015g).

• Worldwide peatlands cover about 500 million hectares of land, some 5-8% of the world's surface.

• They are most extensive in North America, Asia and Europe.

• The remainder are found in tropical areas the most extensive in south-east Asia.

• Overall, hold 10% of freshwater world’s resources.


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Peat (=turf, e.g, in Ireland)Peat types

Peatlandan area with a naturally accumulated peat layer at the surfaceMirea peatland where peat is currently forming and accumulating

Bog, pH 3.2 to 4.2; Ash 3%a peatland which receives water solely from rain and/or snow falling on its surface. Poor trophic status. Up to 12 m thick!!

Fen pH 7 to 8; Ash 10%a peatland which receives water and abundant nutrients from the soil, rock and groundwater as well as rain and/or snow. Up to 2 m.

Elevated Bog

Blanket Bog

Fen

Fen


PeatStructure• Bogs: 98% water! Only 2% solids.• Fens: 85% / 15%• A bog consists of two layers:

• the upper, very thin layer, known as the acrotelm, is only some 30cm deep, and consists of upright stems of the Sphagnum mosses, largely still alive and colourful with their red, yellows and ochre. Water can move rapidly through this layer.

• Below this is a very much thicker bulk of peat, known as the catotelm, where individual plant stems have collapsed under the weight of mosses above them to produce an amorphous, chocolate-coloured mass of Sphagnum fragments. here the water slowly seeps down through the bog over several weeks or even months.


PeatPeat formationPeatlands are composed of deep layers of waterlogged peat and a surface layer of living vegetation. Peat consists of the dead remains of plants (and to a lesser extent of animals) that have accumulated over thousands of years. Peat accumulates in areas where the rate of plant production exceeds the rate of plant decomposition. Complete plant decomposition is prevented in areas where waterlogging occurs.


PeatProxiesWater table oscillations throuhg the fossil record

Testate amoeba

Testate amoebae are routinely used as indicators of past changes in peatland hydrology. These single-celled organisms respond quickly to environmental change, produce decay-resistant and taxonomically distinctive shells and are generally well preserved and abundant in Holocene peat deposits. In oligotrophic peatlands, testate amoeba community composition is primarily controlled by the moisture content of the surface peat, allowing the development of transfer functions to bdepths.


PeatApplication examples• Some bogs are uniquely

suited to natural and anthropogenic airborne particles because their surface layers are only fed by atmospheric inputs (rain, snow, fog, dust).

• Pb is well retained by bogs (adequate pH).

• Stable isotopes allow discriminating between natural and anthropogenic metal abundance, and its origin.

• Metal/Titanium (conservative metal), allows such discrimination.

Peat as an archive of atmospheric pollution

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PeatApplication examples• Pollen-based warm season

temperature reconstruction

• Upper panel is detrended to remove human effects (de- or re-forestation).

• Reconstructed detrended series are compared to instrumentally measured temperatures.

• Correlation begins to be good in 1900 at a decadal resolution.

Lamentowicz et al 2010

Peat pollen record as a paleothermometer


PeatApplication examples• Proxies:

• Normalized testate amoebae water table reconstruction (blue)

• Plant macrofossil Dupont wetness index (green)

• Normalized 14C relative production rate (accretion) (gray)

• Historical solar minima are indicated, and arrows show significant raises in water table.

• Low solar activity results in wetter seasons/periods, increasing the water table and consequently, bog accretion (production).

Chambers et al 2010

Peat proxies record solar activity


PeatApplication examples

• Water table changes (WTC) of several bogs in North America during the last 3000 years (a)

• Microcharcoal particles reveal fire destroying the bog in Michigan (blue) and allows establishing recovery time (resilience; paleo-ecology).

• Statitical removal of long term patterns allows building a composite record of all three bogs (b).

• WTC tightly matches the severe drought periods (yellow).

• Tree rings and dune activity (aeolian transport) match drought periods too.

• Reconstructions of anomalous SST both in the Pacific and in the Atlantic, and of the NAO (Niño) using tree-reings, support all previous proxies and records.

Peat serve to cross-test global climate

hypotheses (Booth et al 2010)

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PeatApplication examplesHg as pollution and temperature proxy

• Galician peat records net accumulation of atmospheric Hg during the last 4000 years.

• Differences in thermal lability of Hg allowed a quantitative paleotemperature reconstruction during that period.

• Natural Hg can be distinguished from anthropogenic Hg, allowing to establish background levels and record mining activities.

• Discriminant analysis allowed to build a relative scale of temperature (Temperature index).

Martínez-Cortizas et al. 1999Miguel Ángel Mateo Mínguez - Centro de Estudios Avanzados de Blanes - CSIC

Peat as a paleo-recordLiterature and web sites

• Dise, N.B, 2009: Peatland responses to global change, Science, 326: 810-811.• Booth, R.K., 2008: Testate amoebae as proxies of mean annual water-table depth in Sphagnum-dominated

peatlands of North America, Journal of Quaternary Science, 23: 43-57.• Booth, R.K., 2010: Testing the climate sensitivity of peat-based paleoclimate reconstructions in mid-

continental North America, Quaternary Science Reviews, 29: 720-731. doi: 10.1016/j.quascirev.2009.11.018• Barber, K.E., 1981: Peat Stratigraphy and Climatic Change—a Palaeoecological Test of the Theory of Cyclic Peat

Bog Regeneration, A A Balkema, Rotterdam.• Vleeschouwer et al., 2010: Peat as an archive of atmospheric pollution and environmental change: a case

study of lead in Europe. PAGES, 18: 20-22.• The Holocene 2001, volume 11, number 5, includes various articles using peat as a paleorecord.

• http://www.lehigh.edu/~rkb205/ (Robert K. Booth web site).• http://www.peat-portal.net/index.cfm?&menuid=115&parentid=113• http://www.ipcc.ie/wptourhome1.html (peatlands around de world)• http://www.doeni.gov.uk/niea/biodiversity/habitats-2/peatlands/about_peatlands.htm

(‘about peatlands’)• http://www.landforms.eu/Caithness/Peat%20formation.htm (peat structure)• http://www.imcg.net/pages/publications/papers.php?lang=EN (Int. Mire Cons. Group; bibliography)


http://www.lehigh.edu/~rkb205/

http://www.peat-portal.net/index.cfm?&menuid=115&parentid=113

http://www.ipcc.ie/wptourhome1.html

http://www.doeni.gov.uk/niea/biodiversity/habitats-2/peatlands/about_peatlands.htm

http://www.landforms.eu/Caithness/Peat%20formation.htm

http://www.imcg.net/pages/publications/papers.php?lang=EN

Peat as a paleo-recordLiterature and web sites

Antonio Martínez-Cortizas: Spanish specialist in the use of peat as a paleorecord.Universidad de Santiago de Compostela, Depto. Edafología y Química Agrícola

[email protected]

• Martínez Cortizas A, Pontevedra-Pombal X, García-Rodeja E, Nóvoa-Muñoz JC, Shotyk, W (1999) Mercury in a Spanish peat bog: archive of climate change and atmospheric metal deposition. Science 284:939–42.

• Martínez Cortizas A, Pontevedra-Pombal X, Nóvoa-Muñoz JC, García-Rodeja E. Four thousand years of atmospheric Pb, Cd and Zn deposition recorded by the ombrotrophic peat bog of Penido Vello (Northwestern Spain) (1997). Water Air Soil Poll, 100:387–403.

• Martínez Cortizas A, García-Rodeja E, Pontevedra-Pombal X, Nóvoa-Muñoz JC, Weis D, Cheburkin A (2002) Atmospheric Pb deposition in Spain during the last 4600 years recorded by two ombrotrophic peat bogs and implications for the use of peat as archive. Sci Total Environ, 292:33–44.

• Martínez Cortizas A, Pontevedra X, Nóvoa JC, Peiteado E, Piñeiro R (2005) Linking changes in atmospheric dust deposition, vegetation change and human activities in north-western Spain during the last 5300 years. The Holocene, 15:698–706.


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Peat as an organic record

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