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| Titel |
Abrupt vegetation transitions characterise long-term Amazonian peatland development |
| VerfasserIn |
K. H. Roucoux, T. R. Baker, W. D. Gosling, E. Honorio Coronado, T. D. Jones, O Lahteenoja, I. T. Lawson |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067966
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| Zusammenfassung |
| Recent investigations of wetlands in western Amazonia have revealed the presence of
extensive peatlands with peat deposits of up to 8 m-thick developing under a variety of
vegetation types (Lähteenoja et al. 2012). Estimated to cover 150,000 km2 (Schulman et al.
1999), these peatlands make a valuable contribution to landscape and biological diversity and
represent globally important carbon stores. In order to understand the processes leading to
peat formation, and the sensitivity of these environments to future climatic change, it is
necessary to understand their long-term history. The extent to which peatland vegetation
changes over time, the stability of particular communities, the controls on transitions between
vegetation types and how these factors relate to the accumulation of organic matter are not yet
known.
We report the first attempt to establish the long-term (millennial scale) vegetation history
of a recently-described peatland site: Quistococha, a palm swamp, or aguajal, close to Iquitos
in northern Peru. The vegetation is dominated by Mauritia flexuosa and Mauritiella
armata and occupies a basin which is thought to be an abandoned channel of the
River Amazon. We obtained a 4 m-long peat sequence from the deepest part of the
basin. AMS-radiocarbon dating yielded a maximum age of 2,212 cal yr BP for
the base of the peat, giving an average accumulation rate of 18 cm per century.
Below the peat are 2 m of uniform, largely inorganic pale grey clays of lacustrine
origin, which are underlain by an unknown thickness of inorganic sandy-silty clay of
fluvial origin. Pollen analysis, carried out at c. 88-year intervals, shows the last 2,212
years to be characterised by the development of at least four distinct vegetation
communities, with peat accumulating throughout. The main phases were: (1) Formation of
Cyperaceae (sedge) fen coincident with peat initiation; (2) A short-lived phase of
local Mauritia/Mauritiella development; (3) Development of mixed wet woodland
with abundant Myrtaceae; (4) Expansion of Mauritia/Mauritiella palm swamp
vegetation c. 1000 years ago representing establishment of the present day vegetation
community.
Our results show that the vegetation at this site has undergone continuous change
throughout the period of peat formation. The sequence of vegetation development is not
straightforward, being characterised by abrupt transitions between vegetation types and
reversals in the apparent trajectory of change. Overall this suggests that the system is highly
dynamic on centennial to millennial timescales. This complexity may reflect vegetation
responses to a combination of external (physical) and internal (biological) drivers and the
presence of thresholds in the system. Future investigations will work towards understanding
the processes that drive these vegetation transitions and predicting peatland vegetation
responses to future climatic change.
References: Lähteenoja, O. et al. (2012) Global Change Biology 18, 164-178; Schulman,
L. et al. (1999) Nature 399, 535-536. |
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