Ecosystem state shifts during long-term development of an Amazonian peatland

Graeme T. Swindles, Paul J. Morris, Bronwen Whitney, Jennifer M. Galloway, Mariusz Gałka, Angela Gallego-sala, Andrew L. Macumber, Donal Mullan, Mark W. Smith, Matthew J. Amesbury, Thomas P. Roland, Hamed Sanei, R.timothy Patterson, Nicole Sanderson, Lauren Parry, Dan J. Charman, Omar Lopez, Elvis Valderamma, Elizabeth J. Watson, Ruza F. IvanovicPaul J. Valdes, T.edward Turner, Outi Lähteenoja

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Abstract

The most carbon (C) dense ecosystems of Amazonia are areas characterised by the presence of peatlands. However, Amazonian peatland ecosystems are poorly understood and are threatened by human activities. Here we present an investigation into long-term ecohydrological controls on C accumulation in an Amazonian peat dome. This site is the oldest peatland yet discovered in Amazonia (peat initiation c. 8.9 ka BP), and developed in three stages; (i) peat initiated in an abandoned river channel with open water and aquatic plants; (ii) inundated forest swamp; and (iii) raised peat dome (since c. 3.9 ka BP). Local burning occurred at least three times in the past 4,500 years. Two phases of particularly rapid C accumulation (c. 6.6-6.1 and c. 4.9-3.9 ka BP), potentially resulting from increased net primary productivity, were seemingly driven by drier conditions associated with widespread drought events. The association of drought phases with major ecosystem state shifts (open water wetland – forest swamp – peat dome) suggests a potential climatic control on the developmental trajectory of this tropical peatland. A third drought phase centred on c. 1.8-1.1 ka BP led to markedly reduced C accumulation and potentially a hiatus during the peat dome stage. Our results suggest that future droughts may lead to phases of rapid C accumulation in some inundated tropical peat swamps, although this can lead ultimately to a shift to ombrotrophy and a subsequent return to slower C accumulation. Conversely, in ombrotrophic peat domes, droughts may lead to reduced C accumulation or even net loss of peat. Increased surface wetness at our site in recent decades may reflect a shift towards a wetter climate in western Amazonia. Amazonian peatlands represent important carbon stores and habitats, and are important archives of past climatic and ecological information. They should form key foci for conservation efforts.
Original languageEnglish
Pages (from-to)738-757
JournalGlobal Change Biology
Volume24
Issue number2
Early online date20 Oct 2017
DOIs
Publication statusPublished - Feb 2018

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