Late Holocene rainforest disturbance in French Guiana

doi:10.1016/S0034-6667(01)00068-9

Review of Palaeobotany and Palynology

Volume 115, Issues 3–4, June 2001, Pages 161-170

https://doi.org/10.1016/S0034-6667(01)00068-9 Get rights and content

Abstract

Palm swamp forest sediments collected in French Guiana provide new data about late Holocene rainforest. Two cores were collected in ‘Les Nouragues’ ecological station (4°05′N, 52°40′W). The lithology shows two different types of sediment, organic peat in the upper part and oxidized clay with low organic content and lacking pollen in the lower part, both separated by a gravel horizon. Radiocarbon dates show that this gravel horizon could have been deposited between 4500 and 3000 yr bp. Pollen analysis carried out on the organic sediments record rainforest disturbances between ca 1520–1380 and 1060–860 cal yr bp suggested by the presence of the pioneer tree species Cecropia together with other shade intolerant genera. Cecropia is recorded for a period that lasts between 660 and 320 years. This abnormal duration for presence of a pioneer species in rainforest is explained by brief and repeated changes in the composition of the canopy asssociated to perturbations of the palm swamp.

Introduction

The history of tropical lowland rainforests, especially during the last several thousand years, is influenced by both climate variability and human impact. Presence of cultivated plant remains (Bush and Colinvaux, 1994), increase of charcoals particles concentration (Kershaw et al., 1997), stone tools (Meggers, 1994), ceramics (Lathrap, 1970), changes in vegetation composition due to slash, burning and agriculture (Semah et al., 1992) are used to evaluate human occupation and impact on rainforest dynamics. On the other hand, climate also had a strong impact on rainforest habitats during the Holocene: flooding, aridity, hurricanes have been recorded and attested through strong changes in vegetation composition and/or increase of charcoals particles (Liu and Colinvaux, 1988, Kershaw, 1995, Vincens et al., 1998, Haberle and Ledru, 2001). Separating both influences has in general been quite difficult.

To document rainforest dynamics during the Late Holocene, we analyzed for the first time two records in French Guiana, a poorly inhabited area and one of the tropical regions with exceptionally high precipitation. Large areas remain covered by mature lowland rainforest, and recently the region was recognized to be of great importance for biodiversity conservation and became an ecological park. Archaeological studies in the Guianan hyper-humid forest region, especially in the Petit Saut area, have not uncovered any remains of human occupation prior to 2100 yr bp.

Section snippets

Present environmental setting

Research was conducted at the Nouragues field station located about 100 km inland (4°05′N, 52°40′W) in a hilly region where several granitic outcrops (‘inselbergs’) occur between 300 and 450 m high (Fig. 1). No longterm data on rainfall are available but between 1990 and 1994, the average annual rainfall was about 2920 mm. The Inter Tropical Convergence Zone (ITCZ) or Meteorological Equator (ME) is the essential precipitation supplier of the tropical zone. The ME shifts latitudinally on both sides

Material and methods

Two cores of 370 (NO 92-2) and 500 cm (NO 92-3) length were drilled at the Nouragues swamp site ca 100 m apart with vibra coring equipment (Martin and Flexor, 1989). Core samples were processed for seed (Charles-Dominique et al., 1998) and pollen content. Samples for pollen analysis were treated following the standard palynological techniques, applying the Luber technique (50% HNO₃ solution and 10% KOH solution). Palynomorphs were separated using a ZnCl₂ solution of density 2 and mounted in

Stratigraphy and chronology

Both cores, NO 92-2 and NO 92-3, collected at the Nouragues site show similarities in their lithology (Fig. 2, Fig. 3). The upper portion of the core is composed of organic peat separated by a level of gravel between ca 130 and 140 cm depth, respectively, from the lower, oxidized part with low organic content and lacking pollen. Radiocarbon dates (Table 1) show that this gravel level could have been deposited between 4500 and 3000 yrs bp. Radiocarbon dates for NO 92-2 at 141 cm depth gave 3040±70 yrs

Palynological records

Results of core NO 92-2 have already been described by Ledru et al. (1997) and a brief summary will be given here using calibrated ¹⁴C dates (Stuiver and Becker, 1993). Results of core NO 92-3 will be compared with NO 92-2 with summary pollen diagrams (Fig. 2, Fig. 3, Fig. 4).

Discussion

Pioneer species colonizing a canopy gap are rapidly taken over by mature forest species in a few decades. The persistence of pioneer plant species such as Cecropia for several centuries would suggest brief and repeated disturbances occurring every 10 to 30 years. Canopy gaps, observed today, are created by the fall of trees either by snapping or uprooting, falling branches, or the death of a tree. Windstorms are a common cause for tree falls. The number and size of gaps formed each year varies

Conclusion

Our results suggest that during the last 4500 yrs bp openings of the rainforest tree cover occurred at least two times in ‘Les Nouragues’. The first one is indicated by a thick gravel level in which pollen was not preserved between ca 4500 and 3000 yrs bp. The second period is shown by the prolonged presence of the pioneer species Cecropia between 1520 and 860 cal yrs bp. This episode is characterized by repeated, short events that contributed to maintaining the canopy gap at Les Nouragues. We are

Acknowledgements

This work is part of the ECOFIT program (ORSTOM/CNRS) that focused on studies in Cameroon, Congo, French Guiana and Brazil between 1992 and 1996. This work benefited also from the discussions and research of Michel Servant, Pierre Charles-Dominique, Louis Martin, Bernard Riéra, Patrick Blanc, Christophe Tardy, Denis Larpin (ECOFIT members); Daniel Sabatier, Marie-Francoise Prévost, Georges Cremers, Jean-Jacques de Granville (ORSTOM Herbarium at Cayenne); Stéphane Vachet, Sylvie Jérémy for the

References (34)

P. Charles-Dominique et al.
Forest perturbations and biodiversity during the last ten thousand years in French Guiana
Acta Oecol.
(1998)
J.F. Dumont et al.
Geodynamic environment of Quaternary morphostructures of the subandean foreland basins of Peru and Bolivia: characteristics and study methods
Quat. Int.
(1994)
S.G. Haberle et al.
Correlations among charcoal records of fires from the past 16,000 years in Indonesia, Papua-New Guinea and Central and South America
Quaternary Research
(2001)
L. Martin et al.
Southern oscillation signal in South American paleoclimate data of the last 7000 years
Quat. Res.
(1993)
A. Vincens et al.
Late Holocene climatic changes in Western equatorial Africa inferred from pollen from Lake Sinnda, Southern Congo
Quat. Res.
(1998)
M. Bush et al.
A 7000-year pollen record from the amazon lowlands, Ecuador
Vegetatio
(1988)
M.B. Bush et al.
A paleoecological perspective of tropical forest disturbance: records from Darien, Panama
Ecology
(1994)
U.M. Chandrashekara et al.
Vegetation and gap dynamics of a tropical wet evergreen forest in the western Ghats of Kerala, India
J. Tropical Ecol.
(1994)
H.F. Diaz et al.
El Niño
(1992)
Durrieu de Madron
Mortalité des arbres en forêt primaire de Guyane francaise
Bois forêts Tropiques
(1994)

K. Faegri et al.

Textbook of Pollen Analysis

(1989)

G.S. Hartshorn

An overview of neotropical forest dynamics

M. Hoff et al.

La banque de donnees ‘Aublet’ de l'Herbier du centre ORSTOM de Cayenne (CAY)

Bull. Jardin Bot. Nat. Belg.

(1989)

S.P. Hubbell et al.

Structure, dynamics, and equilibrium status of old-growth forest on Barro Colorado Island

P. Kershaw

Environmental change in Greater Australia

Transitions Pleistocene to Holocene in Australia and Papua New Guinea

Antiquity

(1995)

A.P. Kershaw et al.

The contribution of humans to past biomass burning in the tropics

D.W. Lathrap

The upper Amazon

Cited by (24)

Atlantic ITCZ variability during the Holocene based on high-resolution speleothem isotope records from northern Venezuela
2023, Quaternary Science Reviews
Few high-resolution paleoclimate proxy records exist in the region located under the direct influence of the Intertropical Convergence Zone (ITCZ) in South America and most of them were retrieved from the Cariaco Basin off the coast of Venezuela. Here we present new ẟ¹⁸O and ẟ¹³C records of Venezuelan speleothems collected in caves adjacent to Cariaco, covering the mid- and late-Holocene. We document previously undetected secular-to multidecadal-scale climate variability in the core region of the ITCZ, which is compared to other high-resolution records from the North Atlantic, Caribbean and tropical South America. Over the mid-Holocene our record exhibits broad swings between periods of reduced (8.3–8.0, 6.5–5.0, 4.1–3.6 ka BP) and increased (8.5, 8.0–6.5, 4.9–4.2 ka BP) rainfall. In particular, between 5.5 and 5.0 ka BP, increases in polar and subpolar North Atlantic ice rafted debris and a reduction in North Atlantic Deep Water (NADW) formation might have contributed to the southward displacement of the North Atlantic Subtropical High (NASH) and the ITCZ, which led to severe dry conditions in north central Venezuela and an enhancement of the South American Monsoon System (SAMS). During the late-Holocene, contrary to data from Cariaco reported in previous studies, our results point to drier conditions during the Medieval Climate Anomaly (MCA, 900–1100 CE), which were further amplified during positive Atlantic Multidecadal Oscillation (AMO) phases. Wet conditions, however, prevailed during the first part of the Little Ice Age (LIA, 1400–1500 CE). No speleothem deposition occurred during the main LIA period, which might be related to drier conditions in response to a southward displacement of the ITCZ that led to major moisture convergence over the SASM domain. Our new records from Venezuela provide a reliable proxy for ITCZ behavior over the Atlantic – South America domain and document past dynamics in relation to other climate systems (NASH and SAMS), while providing new evidence of ITCZ – North Atlantic teleconnections during the Holocene.
Long-term man-environment interactions in the Bolivian Amazon: 8000 years of vegetation dynamics
2016, Quaternary Science Reviews
Citation Excerpt :
Moraceae and Alchornea fluctuate with two pronounced declines around 1400 and 700 cal BP suggesting disturbances in the forests when Cecropia expanded. The genus Cecropia consists of pioneer species following forest clearance as a first succession (Ledru, 2001; Mesquita et al., 1999; Pessenda et al., 2005). Cultural indicators are absent, suggesting a decline of land-use activities.
Only few studies documenting the vegetation history of the Llanos de Moxos, one of the largest seasonally flooded wetland areas in South America, are available and little is known about the environmental impact of pre-Columbian settlements. We use radiocarbon-dated terrestrial plant macrofossils to establish a sound chronology and palynological analyses to reconstruct the vegetation and fire history of the Lago Rogaguado area. The sedimentary pollen and spore record suggests that wetland and wooded savannah (Cerrado) environments occurred around the lake between 8100 and 5800 cal BP. Fire activity was high during this period and was probably connected to the dry Cerrado environments. The pollen evidence suggests early plant cultivation (Zea mays, Annonaceae and Cucurbitaceae) from 6500 cal BP onwards, which is significantly earlier than hitherto assumed for Amazonia. Gallery forests expanded after 5800 cal BP, when fire activity strongly declined. Forest expansion intensified around 2800 cal BP and continued until 2000 cal BP, when forest cover reached its maximum and fire activity its minimum. The late-Holocene forest expansion to the south and the decrease of fire activity may have resulted from a climatic shift to moister conditions (possibly a shorter dry season). New crops (e.g. Avena-type) or adventive plants (e.g. Rumex acetosella-type) document the impact of European economies after ca. 500 cal BP. Land use intensity remained rather stable over the most recent centuries, arguing against a collapse of settlements in response to the arrival of Europeans, as reconstructed from other Amazonian pollen records.
Relative sea-level and climatic changes in the Amazon littoral during the last 500years
2015, Catena
Citation Excerpt :
However, there are still few studies about the effects of tectonics on relative sea-level near the Amazonian coast during the last thousand years. Rainfall changes may have a geographically wider effect on vegetation in northern Brazil (e.g. Van der Hammen, 1974; Absy et al., 1991; Desjardins et al., 1996; Ledru, 2001; Behling and Costa, 2000; Pessenda et al., 2001,2004). Thus, the connection among events recorded in different parts of South America can be attributed to the fluvial system, since river discharge affects mangrove distribution (Cohen et al., 2012).
An integrated approach focused on sedimentology, geochemistry, palynology, C and N isotopes and radiocarbon dating of a sediment core from an herbaceous plain not flooded by tides of the Amapá littoral, near the Amazon River mouth, allowed identification of two phases with marine and terrestrial influences. Mangroves occurred over tidal mud flats with marine influence between > 5610–5470 and 470–310 cal yr BP. The absence of mangrove vegetation since 470–310 cal yr was followed by the transition of brackish water organic matter to terrestrial C₃ plants. Also, the geochemical data indicate a decrease in sea water influence during this last time interval. Likely, the displacement of mangrove forest to lower surfaces was caused by a relative sea-level fall that may be associated with drier conditions with less rainfall during the second part of the last millennium. As suggested by this work, slight relative sea-level fluctuations caused by regional or global climatic change may affect significantly the current mangrove area.
Holocene palaeoenvironmental history of the Amazonian mangrove belt
2012, Quaternary Science Reviews
Citation Excerpt :
These phases have been related to changes in relative sea-level and/or river water discharge, since the current distribution of mangrove on this littoral is mainly controlled by substratum topography and freshwater discharge (Cohen et al., 2005a,b; Lara and Cohen, 2006, 2009). Rainfall variations in the Amazonian hydrographic region (Van der Hammen, 1974; Absy et al., 1991; Desjardins et al., 1996; Behling and Costa, 2000; Ledru, 2001; Pessenda et al., 2001) likely control the volume of the Amazon River, which displays the world's greatest water discharge of 6300 km3 yr−1 (Eisma et al., 1991; Maslin and Burns, 2000; Latrubesse and Franzinelli, 2002). Consequently, during the drier chronologies of the Early and Middle Holocene, the Amazon River's inflow may have been severely reduced (Amarasekera et al., 1997; Toledo and Bush, 2007, 2008).
Wetland dynamic in the northern Brazilian Amazon region during the Holocene was reviewed using palynological, carbon and nitrogen isotopes records, and C/N ratio previously published. The integration of 72 radiocarbon dates recorded in 34 sediment cores sampled along the marine and fluvial littoral, and mainly influenced by the Amazon River, reveals that marine influence and mangrove vegetation were wider than today on the mouth of Amazon River between >8990–8690 and 2300–2230 cal yr BP, forming a continuous mangrove belt along the northern Brazilian Amazon littoral. The establishment of this mangrove strip is a direct consequence of the marine incursion caused by post-glacial sea-level rise possibly associated with tectonic subsidence during the Early and Middle Holocene. In the Late Holocene, in areas influenced by the Amazon River discharge, the mangroves were replaced by freshwater vegetation, and the coast morphology evolved from an estuarine dominated into a rectilinear coast due to coastal progradation. Nevertheless, the marine-influenced littoral, which is currently dominated by mangroves and salt-marsh vegetation, has persistently had brackish water vegetation over tidal mud flats throughout the entire Holocene. Likely, the fragmentation of this continuous mangrove line during the Late Holocene was caused by the increase of river freshwater discharge associated to the change from dry into wet climates in the Late Holocene. This caused a significant decrease of tidal water salinity in areas near the mouth of Amazon River. These changes in the Amazon discharge are probably associated with dry and wet periods in the northern Amazon region during the Holocene.
The impact of climate changes during the Holocene on vegetation in northern French Guiana
2010, Quaternary Research
The impact of climatic changes that occurred during the last glacial maximum and the Holocene on vegetation changes in the Amazon Basin and the Guiana Shield are still widely debated. The aim of our study was to investigate whether major changes in vegetation (i.e. transitions between rainforests and C₄ savannas) occurred in northern French Guiana during the Holocene. We measured variations in the δ¹³C of soil organic matter at eight sites now occupied by forest or savannah. The forest sites were selected to cover two regions (forest refugia and peneplains) which are thought to have experienced different intensities of disturbance during the latest Pleistocene and the Holocene. We found that none of the forest sites underwent major disturbances during the Holocene, i.e. they were not replaced by C₄ savannahs or C₄ forest savannahs for long periods. Our results thus suggest that tropical rainforests in northern French Guiana were resilient to drier climatic conditions during the Holocene. Nevertheless, geographical and vertical variations in the ¹³C of SOM were compatible with minor changes in vegetation, variations in soil processes or in soil physical properties.
Amazonian floodplains harbour minerotrophic and ombrotrophic peatlands
2009, Catena
In tropical lowlands, ecosystems with peat strata are commonly reported from Southeast Asia, but hardly at all from Amazonia. In this paper, we quantify the horizontal distribution of four important plant nutrients (Ca, Mg, K and P) in five peatland sites located in Peruvian Amazonia and the vertical distribution of these nutrients in one of the sites. With this data as well as topography measurements of the peat deposit from one of the sites, we showed that minerotrophic and ombrotrophic peatlands can be detected in Amazonian floodplains. The nutrient-poor ombrotrophic bogs receive nutrients only from atmospheric deposition because of their thick peat layer and convex topography, while the minerotrophic swamps are periodically covered by nutrient-rich floodwater and/or receive nutrient input from surface waters or from groundwater with capillary rise. The existence of such peatlands in the Amazonian lowlands increases the regional habitat diversity and availability of palaeoecological information and probably has implications also for the hydrological dynamics, water quality, and carbon dynamics of the area.

View all citing articles on Scopus

View full text

Late Holocene rainforest disturbance in French Guiana

Abstract

Introduction

Section snippets

Present environmental setting

Material and methods

Stratigraphy and chronology

Palynological records

Discussion

Conclusion

Acknowledgements

Acta Oecol.

Quat. Int.

Quaternary Research

Quat. Res.

Quat. Res.

A 7000-year pollen record from the amazon lowlands, Ecuador

Vegetatio

A paleoecological perspective of tropical forest disturbance: records from Darien, Panama

Ecology

Vegetation and gap dynamics of a tropical wet evergreen forest in the western Ghats of Kerala, India

J. Tropical Ecol.

El Niño

Mortalité des arbres en forêt primaire de Guyane francaise

Bois forêts Tropiques