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

The most carbon (C)‐dense ecosystems of Amazonia are areas characterized 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 a...

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Bibliographic Details
Published in:Global change biology 2018-02, Vol.24 (2), p.738-757
Main Authors: Swindles, Graeme T., Morris, Paul J., Whitney, Bronwen, Galloway, Jennifer M., Gałka, Mariusz, Gallego‐Sala, Angela, Macumber, Andrew L., Mullan, Donal, Smith, Mark W., Amesbury, Matthew J., Roland, Thomas P., Sanei, Hamed, Patterson, R. Timothy, Sanderson, Nicole, Parry, Lauren, Charman, Dan J., Lopez, Omar, Valderamma, Elvis, Watson, Elizabeth J., Ivanovic, Ruza F., Valdes, Paul J., Turner, T. Edward, Lähteenoja, Outi
Format: Article
Language:English
Subjects:
Accumulation
Amazon rainforest
Aquatic ecosystems
Aquatic plants
Archives
Burning
carbon accumulation
climate
Drought
Ecosystems
Forest ecosystems
Forests
Holocene
Moisture content
Net Primary Productivity
palaeoecology
Peat
Peatlands
Peru
Phases
Primary production
Rivers
Surface wetness
swamp
Swamps
Trajectory control
Tropical climate
tropical peatland
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Summary:The most carbon (C)‐dense ecosystems of Amazonia are areas characterized 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 ca. 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 ca. 3.9 ka BP). Local burning occurred at least three times in the past 4,500 years. Two phases of particularly rapid C accumulation (ca. 6.6–6.1 and ca. 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 ca. 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. We investigate the developmental history of the oldest peatland discovered in Amazonia to date. The peatland developed in three distinct changes: (i) peat initiated in an abandoned river channel with open water; (ii) inundated forest swamp; and (iii) raised peat dome. We find that a combination of internal factors and climate change has driven changes in the rate of carbon accumulation through time.
ISSN:1354-1013
1365-2486
DOI:10.1111/gcb.13950