TY - GEN
T1 - Influence of flooding variability on the vegetation development of Amazonian peatlands
AU - Sassoon, D.
AU - Roucoux, K. H.
AU - Lawson, I. T.
AU - Fletcher, W. J.
AU - Ryan, P.
AU - Honorio Coronado, E. N.
AU - Del Aguila Pasquel, J.
AU - Bishop, T.
AU - Åkesson, C. M.
PY - 2023/12
Y1 - 2023/12
N2 - Over the past two decades, the existence of intact peatlands in lowland
Amazonia has been demonstrated, including a vast area of potential
peat-forming vegetation of around 43,617 km2 in the
Pastaza-Marañón Foreland Basin (PMFB), in the Loreto Department of
north-east Peru. Peat sampling and floristic assessments have revealed
the presence of peat in four ecosystem types in the PMFB: palm swamps,
peatland pole forests, open peatlands, and, more rarely, in seasonally
flooded forests. However, recent field investigations and palynological
studies show that temporal changes in vegetation in peatlands may have
been driven by changes in the degree of flooding, suggesting greater
complexity in the controls on peatland development and in the
spatiotemporal relationships between ecosystems than current conceptual
models allow. Here we present new high-resolution palynological,
geochemical and radiocarbon data from an open peatland sampled in the
PMFB near San Roque village on the Marañón river. Our study aims to: (1)
reconstruct past vegetation changes; (2) investigate the interaction
between the fluvial system and the peatland’s vegetation dynamics over
time; (3) determine how patterns of ecological and fluvial change at San
Roque compare with records from other peatland types in the wider PMFB.
Downcore palynology on the dated SAR_T3_03_B peat core provides a
vegetation record spanning the last 4,300 years documenting changes in
ecological associations over time. Between 4,300 and 3,180 cal yr BP,
prior to peat accumulation, our data shows pronounced fluvial influence
with high amounts of inorganic material and pollen assemblages from
taxa related to open water conditions. Since the beginning of peat
accumulation around 3,180 Cal yr BP, palynological and geochemical data
suggest conditions related to predominantly herbaceous communities. Core
scanning micro-XRF provides proxy evidence for episodes of
fluvially-derived minerogenic input during the period of peat
accumulation (3,180–440 Cal yr BP). Simultaneous increases in
flood-tolerant taxa (e.g. Symmeria paniculata, Alchornea
sp., Myrtaceae) support the inference of intervals with increased
frequency and depth of river flooding. From around 440 Cal yr BP, we
infer the establishment of M. flexuosa palms linked to lower
flooding, which persists today. Compared with other regional sequences,
the San Roque record is distinctive because of this notable influence of
flooding regime on the ecosystem, which impacted on the vegetation
succession through changes in flood levels and nutrient inputs. The
dynamics of the sediment-laden Marañón River therefore emerges as a
major driver in vegetation change and trajectory of peatland development
during the last four millennia.
AB - Over the past two decades, the existence of intact peatlands in lowland
Amazonia has been demonstrated, including a vast area of potential
peat-forming vegetation of around 43,617 km2 in the
Pastaza-Marañón Foreland Basin (PMFB), in the Loreto Department of
north-east Peru. Peat sampling and floristic assessments have revealed
the presence of peat in four ecosystem types in the PMFB: palm swamps,
peatland pole forests, open peatlands, and, more rarely, in seasonally
flooded forests. However, recent field investigations and palynological
studies show that temporal changes in vegetation in peatlands may have
been driven by changes in the degree of flooding, suggesting greater
complexity in the controls on peatland development and in the
spatiotemporal relationships between ecosystems than current conceptual
models allow. Here we present new high-resolution palynological,
geochemical and radiocarbon data from an open peatland sampled in the
PMFB near San Roque village on the Marañón river. Our study aims to: (1)
reconstruct past vegetation changes; (2) investigate the interaction
between the fluvial system and the peatland’s vegetation dynamics over
time; (3) determine how patterns of ecological and fluvial change at San
Roque compare with records from other peatland types in the wider PMFB.
Downcore palynology on the dated SAR_T3_03_B peat core provides a
vegetation record spanning the last 4,300 years documenting changes in
ecological associations over time. Between 4,300 and 3,180 cal yr BP,
prior to peat accumulation, our data shows pronounced fluvial influence
with high amounts of inorganic material and pollen assemblages from
taxa related to open water conditions. Since the beginning of peat
accumulation around 3,180 Cal yr BP, palynological and geochemical data
suggest conditions related to predominantly herbaceous communities. Core
scanning micro-XRF provides proxy evidence for episodes of
fluvially-derived minerogenic input during the period of peat
accumulation (3,180–440 Cal yr BP). Simultaneous increases in
flood-tolerant taxa (e.g. Symmeria paniculata, Alchornea
sp., Myrtaceae) support the inference of intervals with increased
frequency and depth of river flooding. From around 440 Cal yr BP, we
infer the establishment of M. flexuosa palms linked to lower
flooding, which persists today. Compared with other regional sequences,
the San Roque record is distinctive because of this notable influence of
flooding regime on the ecosystem, which impacted on the vegetation
succession through changes in flood levels and nutrient inputs. The
dynamics of the sediment-laden Marañón River therefore emerges as a
major driver in vegetation change and trajectory of peatland development
during the last four millennia.
M3 - Conference contribution
T3 - EGU General Assembly Conference Abstracts
BT - EGU General Assembly Conference Abstracts
ER -