Ramon Aravena
Datos Biográficos
| ID | 4304772 |
|---|---|
| NOMBRE | Ramon Aravena |
| NOMBRES | Ramon |
| APELLIDO | Aravena |
| FIRMA | ARAVENA R |
| AFILIACIONES | University of Waterloo |
| ORCID | 0000-0003-2582-3639 |
| VERIFICADO | Sí |
| TOTAL DE OBRAS | 25 |
| TOTAL DE CITAS | 147 |
| TOTAL COMO AUTOR | 25 |
| TOTAL COMO EDITOR | 0 |
| PRIMER AÑO DE PUBLICACIÓN | 1988 |
| AÑO MÁS RECIENTE DE PUBLICACIÓN | 2009 |
| ÍNDICE H | 6 |
The evolution of a tropical rainforest/grassland mosaic in southeastern Brazil since 28,000 14 C yr BP based on carbon isotopes and pollen records
The lack of paleoecological records from the montane Atlantic Rainforest of coastal Brazil, a hotspot of biological diversity, has been a major obstacle to our understanding of the vegetational changes since the last glacial cycle. We present carbon isotope and pollen records to assess the impact of the glaciation on the native vegetation of the Serra do Mar rainforest in São Paulo, Brazil. From ca. 28,000 to ∼ 22,000 14 C yr BP, a subtropical fo…
Holocene palaeoenvironmental reconstruction in norteastern Brazi inferred from polen,, charcoal and carboon isotope records
Soils in the Barreirinhas region, Maranhao State, were sampled for 613 C analysis and buried charcoal fragments in the soils were radiocarbon dated. Three soil profiles collected in forested areas around the Lagoa do Caqö and one in a woody savanna (mixture of non-arboreal and arboreal species) located approximately 10 km southeast of the Lagoa were studied. A high-resolution pollen record was obtained from lake sediments, showing that forest veg…
Vegetation dynamics during the late Pleistocene in the Barreirinhas region, Maranhão State, northeastern Brazil, based on carbon Isotopes in soil organic matter
The study place is in the Barreirinhas region, Maranhão State, northeastern Brazil. A vegetation transect of 78 km was studied among four vegetation types: Restinga (coastal vegetation), Cerrado (woody savanna), Cerrad"o (dense woody savanna), and Forest, as well as three forested sites around Lagoa do Caçó, located approximately 10 km of the transect. Soil profiles in this transect were sampled for δ 13 C analysis, as well as buried charcoal fra…
Rapid development of an unusual peat-accumulating ecosystem in the Chilean Altiplano
Stratigraphic relationships, radiocarbon dating, sediment and peat characteristics, and rates of peat and carbon accumulation from a soligenous peatland, or “bofedal,” in the Chilean Altiplano shows the peatland to be unusually young, dynamic, and sensitive to environmental changes. The site lies in the National Park Nevado de Tres Cruces in the puna desert grassland at an elevation of 4300 m a.s.l. Eight peat cores were extracted from a 1.75-km …
Holocene palaeoenvironmental evolution in the São Paulo State (Brazil), based on anthracology and soil δ13C analysis
This paper presents a reconstruction of the Holocene palaeoenvironmental evolution in the central São Paulo State (Brazil) based on anthracological analyses, in association with soil isotopic composition (δ 13 C) and radiocarbon dating from four sites. Anatomical identification of charcoal particles allows the reconstitution of past plant associations, and consequently of the vegetation and climate history. Rather precise interpretations may be a…
Late Quaternary Vegetation Dynamics in the Southern Amazon Basin Inferred from Carbon Isotopes in Soil Organic Matter
Carbon isotopes of soil organic matter (SOM) were used to evaluate and establish the chronology of the vegetation dynamics of an ecosystem presently composed of savannas surrounded by forests. The study was carried out on a 200-km transect along highway BR 319, on the border of Amazonas and Rondônia states, in southern Amazon, Brazil. Large ranges in δ 13 C values were observed in SOM collected from profiles in the savanna (−27 to −14‰) and fores…
Origin and dynamics of soil organic matter and vegetation changes during the Holocene in a forest-savanna transition zone, Brazilian Amazon region
Carbon isotope data on soil organic matter (SOM) were collected along an ecosystem transect 90 m in length that includes a tropical forest on the plateau, a transitional forest-savanna and savanna in a depression. Total organic carbon data show a significant increase in carbon content from sites representing forest ecosystem to sites representing savanna ecosystem. It was hypothesized that carbon accumulation in the depression is controlled by fl…
Radiocarbon Dating of Total Soil Organic Matter and Humin Fraction and Its Comparison with 14 C Ages of Fossil Charcoal
During the last decade radiocarbon dating has been used extensively in distinct regions of Brazil to provide information about soil chronology in paleoenvironmental studies. This paper presents 14 C data of soil organic matter (SOM), humin fraction, and charcoal in several soil profiles under natural vegetation from different Brazil locations (north, central, and southeast regions). The main objective is to compare the obtained 14 C dating of tot…
Holocene Paleohydrology and Paleoclimate at Treeline, North-Central Russia, Inferred from Oxygen Isotope Records in Lake Sediment Cellulose
Lake-water oxygen-isotope histories for three lakes in northern Russia, derived from the cellulose oxygen-isotope stratigraphies of sediment cores, provide the basis for preliminary reconstruction of Holocene paleohydrology in two regions along the boreal treeline. Deconvolution of shifting precipitation δ 18 O from secondary evaporative isotopic enrichment is aided by knowledge of the distribution of isotopes in modern precipitation, the isotopi…
Holocene Treeline History and Climate Change Across Northern Eurasia
Radiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern …
Carbon accumulation in permafrost peatlands in the Northwest Territories and Nunavut, Canada
Average long-term apparent rates of carbon (C) accumulation (LARCA) were estimated for four peat cores from Arctic and Subarctic Canada. Detailed analyses of dry bulk-density and C content were used to determine variations in C accumulation rates throughout the cores. LARCA range from 12.5 to 16.5 g C m -2 yr -1 over the past 6700-10000 years. Rates are lower for the surface layers of Arctic high-centred peat polygons, at 5.3 to 7.1 g C m -2 yr -…
Changes in carbon and nitrogen cycling during tree-line retreat recorded in the isotopic content of lacustrine organic matter, western Taimyr Peninsula, Russia
Bulk organic and cellulose stable carbon isotope and bulk organic nitrogen isotope profiles from the sediments of a small tundra lake on the western Taimyr Peninsula, Russia, show changes that are correlated with climate cooling and treeline retreat at c. 4000 14 C years BP. Increased soil organic matter decomposition, combined with a moist climate, probably provided a 13 C-depleted source of CO 2(aq) to lake phytoplankton thriving under favourab…
The carbon isotope record in soils along a forest-cerrado ecosystem transect
This paper presents carbon isotope data on soil organic matter (SOM) collected along an ecosystem transect that includes a wooded savannah (cerrado), a tropical semideciduous forest (cerradão), a forest tran sition type and a tropical forest. The study area is located in the Rondonia state, southwestern Brazilian Amazon region. 14 C data of total soil organic matter and charcoal indicate that the organic matter in these soils is at least Holocene…
Holocene Climate Effects on the Development of a Peatland on the Tuktoyaktuk Peninsula, Northwest Territories
Six cores were collected from a small peatland on the Tuktoyaktuk Peninsula, yielding up to 1.8 m of organic material and 1.2 m of ice-rich material. Stratigraphic relationships, radiocarbon dating, and pollen, plant macrofossil, and isotopic analyses are used to reconstruct the developmental history of the peatland. Organic matter began to accumulate in the basin about 7200 yr B.P., during a period when the climate is thought to have been warmer…
C Dating and Stable Carbon Isotopes of Soil Organic Matter in Forest–Savanna Boundary Areas in the Southern Brazilian Amazon Region
This study, which was carried out in the southern Brazilian Amazon region (Rondônia state and Humaitá, Southern Amazon state), presents and discusses the significance of carbon isotope data measured in soil profiles collected across natural boundaries of forest to savanna vegetation. The main objective of this study was to evaluate the expansion-regression dynamics of these vegetation units in relation to climate changes during the Holocene. 14 C…
Natural Radiocarbon Measurements in Brazilian Soils Developed on Basic Rocks
This paper presents 14 C, 13 C and chemical data of soil organic matter (SOM) in three soil profiles under native forests from Brazil: Londrina (southern), Piracicaba (southeastern) and Altamira (northern). The main objective is to use carbon isotopes in tropical and subtropical soils of Brazil to provide information about vegetation changes that occurred in relation to climate changes during the Holocene. 14 C data from SOM indicate that the org…
The Use of Carbon Isotopes ( 13 C, 14 C) in Soil to Evaluate Vegetation Changes During the Holocene in Central Brazil
This paper presents carbon isotope data measured in three soil profiles from the Salitre area, Central Brazil. The study forms part of a research project on tropical and subtropical soils in Brazil, in which the main objective is to use carbon isotopes to provide information about vegetation changes that have occurred in relation to climate changes during the Holocene. 14 C data from charcoal samples and soil organic matter (SOM) indicate that th…
Isotope hydrology and geochemistry of Northern Chile groundwaters
Hidrología isotópica y geoquímica de las aguas subterráneas del Norte de Chile En este trabajo se presenta un resumen de estudios que se han realizado en el Norte de Chile, en acuíferos localizados en la Pampa del Tamarugal y en el Salar de Atacama. Los principales objetivos de esos estudios fueron obtener información sobre el origen y el tiempo de residencia del agua subterránea, calidad química del agua, tasas de evaporación desde los salares y…
Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada
Radiocarbon dating and carbon isotope analyses of deep peat and gases in a small ombrogenous peatland in northwestern Ontario reveals the presence of old gases at depth that are 1000–2000 yr younger than the enclosing peat. We suggest that the most likely explanation to account for this age discrepancy is the downward movement by advection of younger dissolved organic carbon for use by fermentation and methanogens bacteria. This study identifies …
Carbon Isotope Composition of Lake Sediments in Relation to Lake Productivity and Radiocarbon Dating
Carbon-13 profiles and radiocarbon dates were obtained from two Canadian kettle basins having similar geological and hydrological characteristics to develop criteria for evaluating the validity of radiocarbon dates on lake sediment from basins in calcareous terrain. Radiocarbon dates from a site in Alberta show a variable hard-water effect related to local hydrological changes during postglacial history of the lake basin, whereas radiocarbon date…
Sources and Transformation of Dissolved Organic Carbon in the Harp Lake Forested Catchment
The 14 C content of dissolved organic carbon (DOC) in streams, soil water and groundwaters in the Harp Lake catchment in Ontario, Canada, reflect a mixture of DOC sources, including both contemporary plant material and 14 C-depleted soil organic matter. The concentration and isotopic content of DOC in streams is highly variable, reflecting the complex flow path of the source water entering the streams. The characteristics of groundwater DOC are s…
Evaluating Dissolved Inorganic Carbon Cycling in a Forested Lake Watershed Using Carbon Isotopes
Dissolved inorganic carbon (DIC) is the main acid buffer in forested lake watersheds in Canada. We used carbon isotopes ( 13 C, 14 C) to evaluate the production and cycling of DIC in an acid-sensitive lake watershed of the Precambrian Shield. Soil CO 2 , groundwater and stream DIC were characterized chemically and isotopically. Soil CO 2 concentration profiles reflect both changes in production and in losses due to diffusion. δ 13 C soil CO 2 pro…
The Geochemistry and Evolution of Natural Organic Solutes in Groundwater
This paper describes the organic carbon cycle of the recharge environment of a shallow, sandy aquifer, with an emphasis on the origin, flux and geochemical evolution of dissolved organic carbon using liquid chromatography, carbon isotopes and GC-MS techniques. The two components of DOC investigated are hydrophobic acids and C 1 -C 10 hydrophilic compounds. The 14 C activity of these components of the DOC was measured using TAMS. 14 C analyses of …
New Possibilities for 14C Measurements by Liquid Scintillation Counting
Results of intercomparison tests are presented on samples analyzed using gas and liquid scintillation techniques to study the capability of the LKB Quantulus to count an organic solution used for direct absorption of CO 2 and samples with low carbon content. Good agreement was obtained for small samples compared to standard sample size and for the direct absorption compared with the traditional techniques
Growth Rates of Natural Amazonian Forest Trees Based on Radiocarbon Measurements
Evergreen trees in the tropical rain forest of the Amazonas Basin can produce growth rings which are not necessarily related to annual events. Therefore, estimation of growth rate cannot be done by dendrochronology. This report presents a technique for determining the growth rate of these trees based on radiocarbon measurements of two segments of equal radial distance from the outer part of the tree trunk. The measured 14 C activity is compared t…
Radiocarbon Dating of Total Soil Organic Matter and Humin Fraction and Its Comparison with 14 C Ages of Fossil Charcoal
During the last decade radiocarbon dating has been used extensively in distinct regions of Brazil to provide information about soil chronology in paleoenvironmental studies. This paper presents 14 C data of soil organic matter (SOM), humin fraction, and charcoal in several soil profiles under natural vegetation from different Brazil locations (north, central, and southeast regions). The main objective is to compare the obtained 14 C dating of tot…
Origin and dynamics of soil organic matter and vegetation changes during the Holocene in a forest-savanna transition zone, Brazilian Amazon region
Carbon isotope data on soil organic matter (SOM) were collected along an ecosystem transect 90 m in length that includes a tropical forest on the plateau, a transitional forest-savanna and savanna in a depression. Total organic carbon data show a significant increase in carbon content from sites representing forest ecosystem to sites representing savanna ecosystem. It was hypothesized that carbon accumulation in the depression is controlled by fl…
C Dating and Stable Carbon Isotopes of Soil Organic Matter in Forest–Savanna Boundary Areas in the Southern Brazilian Amazon Region
This study, which was carried out in the southern Brazilian Amazon region (Rondônia state and Humaitá, Southern Amazon state), presents and discusses the significance of carbon isotope data measured in soil profiles collected across natural boundaries of forest to savanna vegetation. The main objective of this study was to evaluate the expansion-regression dynamics of these vegetation units in relation to climate changes during the Holocene. 14 C…
The carbon isotope record in soils along a forest-cerrado ecosystem transect
This paper presents carbon isotope data on soil organic matter (SOM) collected along an ecosystem transect that includes a wooded savannah (cerrado), a tropical semideciduous forest (cerradão), a forest tran sition type and a tropical forest. The study area is located in the Rondonia state, southwestern Brazilian Amazon region. 14 C data of total soil organic matter and charcoal indicate that the organic matter in these soils is at least Holocene…
Holocene palaeoenvironmental evolution in the São Paulo State (Brazil), based on anthracology and soil δ13C analysis
This paper presents a reconstruction of the Holocene palaeoenvironmental evolution in the central São Paulo State (Brazil) based on anthracological analyses, in association with soil isotopic composition (δ 13 C) and radiocarbon dating from four sites. Anatomical identification of charcoal particles allows the reconstitution of past plant associations, and consequently of the vegetation and climate history. Rather precise interpretations may be a…
Carbon accumulation in permafrost peatlands in the Northwest Territories and Nunavut, Canada
Average long-term apparent rates of carbon (C) accumulation (LARCA) were estimated for four peat cores from Arctic and Subarctic Canada. Detailed analyses of dry bulk-density and C content were used to determine variations in C accumulation rates throughout the cores. LARCA range from 12.5 to 16.5 g C m -2 yr -1 over the past 6700-10000 years. Rates are lower for the surface layers of Arctic high-centred peat polygons, at 5.3 to 7.1 g C m -2 yr -…
The Use of Carbon Isotopes ( 13 C, 14 C) in Soil to Evaluate Vegetation Changes During the Holocene in Central Brazil
This paper presents carbon isotope data measured in three soil profiles from the Salitre area, Central Brazil. The study forms part of a research project on tropical and subtropical soils in Brazil, in which the main objective is to use carbon isotopes to provide information about vegetation changes that have occurred in relation to climate changes during the Holocene. 14 C data from charcoal samples and soil organic matter (SOM) indicate that th…
Natural Radiocarbon Measurements in Brazilian Soils Developed on Basic Rocks
This paper presents 14 C, 13 C and chemical data of soil organic matter (SOM) in three soil profiles under native forests from Brazil: Londrina (southern), Piracicaba (southeastern) and Altamira (northern). The main objective is to use carbon isotopes in tropical and subtropical soils of Brazil to provide information about vegetation changes that occurred in relation to climate changes during the Holocene. 14 C data from SOM indicate that the org…
Changes in carbon and nitrogen cycling during tree-line retreat recorded in the isotopic content of lacustrine organic matter, western Taimyr Peninsula, Russia
Bulk organic and cellulose stable carbon isotope and bulk organic nitrogen isotope profiles from the sediments of a small tundra lake on the western Taimyr Peninsula, Russia, show changes that are correlated with climate cooling and treeline retreat at c. 4000 14 C years BP. Increased soil organic matter decomposition, combined with a moist climate, probably provided a 13 C-depleted source of CO 2(aq) to lake phytoplankton thriving under favourab…
Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada
Radiocarbon dating and carbon isotope analyses of deep peat and gases in a small ombrogenous peatland in northwestern Ontario reveals the presence of old gases at depth that are 1000–2000 yr younger than the enclosing peat. We suggest that the most likely explanation to account for this age discrepancy is the downward movement by advection of younger dissolved organic carbon for use by fermentation and methanogens bacteria. This study identifies …
Holocene palaeoenvironmental reconstruction in norteastern Brazi inferred from polen,, charcoal and carboon isotope records
Soils in the Barreirinhas region, Maranhao State, were sampled for 613 C analysis and buried charcoal fragments in the soils were radiocarbon dated. Three soil profiles collected in forested areas around the Lagoa do Caqö and one in a woody savanna (mixture of non-arboreal and arboreal species) located approximately 10 km southeast of the Lagoa were studied. A high-resolution pollen record was obtained from lake sediments, showing that forest veg…
Growth Rates of Natural Amazonian Forest Trees Based on Radiocarbon Measurements
Evergreen trees in the tropical rain forest of the Amazonas Basin can produce growth rings which are not necessarily related to annual events. Therefore, estimation of growth rate cannot be done by dendrochronology. This report presents a technique for determining the growth rate of these trees based on radiocarbon measurements of two segments of equal radial distance from the outer part of the tree trunk. The measured 14 C activity is compared t…
Sources and Transformation of Dissolved Organic Carbon in the Harp Lake Forested Catchment
The 14 C content of dissolved organic carbon (DOC) in streams, soil water and groundwaters in the Harp Lake catchment in Ontario, Canada, reflect a mixture of DOC sources, including both contemporary plant material and 14 C-depleted soil organic matter. The concentration and isotopic content of DOC in streams is highly variable, reflecting the complex flow path of the source water entering the streams. The characteristics of groundwater DOC are s…
Evaluating Dissolved Inorganic Carbon Cycling in a Forested Lake Watershed Using Carbon Isotopes
Dissolved inorganic carbon (DIC) is the main acid buffer in forested lake watersheds in Canada. We used carbon isotopes ( 13 C, 14 C) to evaluate the production and cycling of DIC in an acid-sensitive lake watershed of the Precambrian Shield. Soil CO 2 , groundwater and stream DIC were characterized chemically and isotopically. Soil CO 2 concentration profiles reflect both changes in production and in losses due to diffusion. δ 13 C soil CO 2 pro…
The Geochemistry and Evolution of Natural Organic Solutes in Groundwater
This paper describes the organic carbon cycle of the recharge environment of a shallow, sandy aquifer, with an emphasis on the origin, flux and geochemical evolution of dissolved organic carbon using liquid chromatography, carbon isotopes and GC-MS techniques. The two components of DOC investigated are hydrophobic acids and C 1 -C 10 hydrophilic compounds. The 14 C activity of these components of the DOC was measured using TAMS. 14 C analyses of …
New Possibilities for 14C Measurements by Liquid Scintillation Counting
Results of intercomparison tests are presented on samples analyzed using gas and liquid scintillation techniques to study the capability of the LKB Quantulus to count an organic solution used for direct absorption of CO 2 and samples with low carbon content. Good agreement was obtained for small samples compared to standard sample size and for the direct absorption compared with the traditional techniques
Growth Rates of Natural Amazonian Forest Trees Based on Radiocarbon Measurements
Evergreen trees in the tropical rain forest of the Amazonas Basin can produce growth rings which are not necessarily related to annual events. Therefore, estimation of growth rate cannot be done by dendrochronology. This report presents a technique for determining the growth rate of these trees based on radiocarbon measurements of two segments of equal radial distance from the outer part of the tree trunk. The measured 14 C activity is compared t…
The Geochemistry and Evolution of Natural Organic Solutes in Groundwater
This paper describes the organic carbon cycle of the recharge environment of a shallow, sandy aquifer, with an emphasis on the origin, flux and geochemical evolution of dissolved organic carbon using liquid chromatography, carbon isotopes and GC-MS techniques. The two components of DOC investigated are hydrophobic acids and C 1 -C 10 hydrophilic compounds. The 14 C activity of these components of the DOC was measured using TAMS. 14 C analyses of …
New Possibilities for 14C Measurements by Liquid Scintillation Counting
Results of intercomparison tests are presented on samples analyzed using gas and liquid scintillation techniques to study the capability of the LKB Quantulus to count an organic solution used for direct absorption of CO 2 and samples with low carbon content. Good agreement was obtained for small samples compared to standard sample size and for the direct absorption compared with the traditional techniques
Carbon Isotope Composition of Lake Sediments in Relation to Lake Productivity and Radiocarbon Dating
Carbon-13 profiles and radiocarbon dates were obtained from two Canadian kettle basins having similar geological and hydrological characteristics to develop criteria for evaluating the validity of radiocarbon dates on lake sediment from basins in calcareous terrain. Radiocarbon dates from a site in Alberta show a variable hard-water effect related to local hydrological changes during postglacial history of the lake basin, whereas radiocarbon date…
Sources and Transformation of Dissolved Organic Carbon in the Harp Lake Forested Catchment
The 14 C content of dissolved organic carbon (DOC) in streams, soil water and groundwaters in the Harp Lake catchment in Ontario, Canada, reflect a mixture of DOC sources, including both contemporary plant material and 14 C-depleted soil organic matter. The concentration and isotopic content of DOC in streams is highly variable, reflecting the complex flow path of the source water entering the streams. The characteristics of groundwater DOC are s…
Evaluating Dissolved Inorganic Carbon Cycling in a Forested Lake Watershed Using Carbon Isotopes
Dissolved inorganic carbon (DIC) is the main acid buffer in forested lake watersheds in Canada. We used carbon isotopes ( 13 C, 14 C) to evaluate the production and cycling of DIC in an acid-sensitive lake watershed of the Precambrian Shield. Soil CO 2 , groundwater and stream DIC were characterized chemically and isotopically. Soil CO 2 concentration profiles reflect both changes in production and in losses due to diffusion. δ 13 C soil CO 2 pro…
Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada
Radiocarbon dating and carbon isotope analyses of deep peat and gases in a small ombrogenous peatland in northwestern Ontario reveals the presence of old gases at depth that are 1000–2000 yr younger than the enclosing peat. We suggest that the most likely explanation to account for this age discrepancy is the downward movement by advection of younger dissolved organic carbon for use by fermentation and methanogens bacteria. This study identifies …
Isotope hydrology and geochemistry of Northern Chile groundwaters
Hidrología isotópica y geoquímica de las aguas subterráneas del Norte de Chile En este trabajo se presenta un resumen de estudios que se han realizado en el Norte de Chile, en acuíferos localizados en la Pampa del Tamarugal y en el Salar de Atacama. Los principales objetivos de esos estudios fueron obtener información sobre el origen y el tiempo de residencia del agua subterránea, calidad química del agua, tasas de evaporación desde los salares y…
Natural Radiocarbon Measurements in Brazilian Soils Developed on Basic Rocks
This paper presents 14 C, 13 C and chemical data of soil organic matter (SOM) in three soil profiles under native forests from Brazil: Londrina (southern), Piracicaba (southeastern) and Altamira (northern). The main objective is to use carbon isotopes in tropical and subtropical soils of Brazil to provide information about vegetation changes that occurred in relation to climate changes during the Holocene. 14 C data from SOM indicate that the org…
The Use of Carbon Isotopes ( 13 C, 14 C) in Soil to Evaluate Vegetation Changes During the Holocene in Central Brazil
This paper presents carbon isotope data measured in three soil profiles from the Salitre area, Central Brazil. The study forms part of a research project on tropical and subtropical soils in Brazil, in which the main objective is to use carbon isotopes to provide information about vegetation changes that have occurred in relation to climate changes during the Holocene. 14 C data from charcoal samples and soil organic matter (SOM) indicate that th…
Holocene Climate Effects on the Development of a Peatland on the Tuktoyaktuk Peninsula, Northwest Territories
Six cores were collected from a small peatland on the Tuktoyaktuk Peninsula, yielding up to 1.8 m of organic material and 1.2 m of ice-rich material. Stratigraphic relationships, radiocarbon dating, and pollen, plant macrofossil, and isotopic analyses are used to reconstruct the developmental history of the peatland. Organic matter began to accumulate in the basin about 7200 yr B.P., during a period when the climate is thought to have been warmer…
C Dating and Stable Carbon Isotopes of Soil Organic Matter in Forest–Savanna Boundary Areas in the Southern Brazilian Amazon Region
This study, which was carried out in the southern Brazilian Amazon region (Rondônia state and Humaitá, Southern Amazon state), presents and discusses the significance of carbon isotope data measured in soil profiles collected across natural boundaries of forest to savanna vegetation. The main objective of this study was to evaluate the expansion-regression dynamics of these vegetation units in relation to climate changes during the Holocene. 14 C…
The carbon isotope record in soils along a forest-cerrado ecosystem transect
This paper presents carbon isotope data on soil organic matter (SOM) collected along an ecosystem transect that includes a wooded savannah (cerrado), a tropical semideciduous forest (cerradão), a forest tran sition type and a tropical forest. The study area is located in the Rondonia state, southwestern Brazilian Amazon region. 14 C data of total soil organic matter and charcoal indicate that the organic matter in these soils is at least Holocene…
Changes in carbon and nitrogen cycling during tree-line retreat recorded in the isotopic content of lacustrine organic matter, western Taimyr Peninsula, Russia
Bulk organic and cellulose stable carbon isotope and bulk organic nitrogen isotope profiles from the sediments of a small tundra lake on the western Taimyr Peninsula, Russia, show changes that are correlated with climate cooling and treeline retreat at c. 4000 14 C years BP. Increased soil organic matter decomposition, combined with a moist climate, probably provided a 13 C-depleted source of CO 2(aq) to lake phytoplankton thriving under favourab…
Holocene Paleohydrology and Paleoclimate at Treeline, North-Central Russia, Inferred from Oxygen Isotope Records in Lake Sediment Cellulose
Lake-water oxygen-isotope histories for three lakes in northern Russia, derived from the cellulose oxygen-isotope stratigraphies of sediment cores, provide the basis for preliminary reconstruction of Holocene paleohydrology in two regions along the boreal treeline. Deconvolution of shifting precipitation δ 18 O from secondary evaporative isotopic enrichment is aided by knowledge of the distribution of isotopes in modern precipitation, the isotopi…
Holocene Treeline History and Climate Change Across Northern Eurasia
Radiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern …
Carbon accumulation in permafrost peatlands in the Northwest Territories and Nunavut, Canada
Average long-term apparent rates of carbon (C) accumulation (LARCA) were estimated for four peat cores from Arctic and Subarctic Canada. Detailed analyses of dry bulk-density and C content were used to determine variations in C accumulation rates throughout the cores. LARCA range from 12.5 to 16.5 g C m -2 yr -1 over the past 6700-10000 years. Rates are lower for the surface layers of Arctic high-centred peat polygons, at 5.3 to 7.1 g C m -2 yr -…
Late Quaternary Vegetation Dynamics in the Southern Amazon Basin Inferred from Carbon Isotopes in Soil Organic Matter
Carbon isotopes of soil organic matter (SOM) were used to evaluate and establish the chronology of the vegetation dynamics of an ecosystem presently composed of savannas surrounded by forests. The study was carried out on a 200-km transect along highway BR 319, on the border of Amazonas and Rondônia states, in southern Amazon, Brazil. Large ranges in δ 13 C values were observed in SOM collected from profiles in the savanna (−27 to −14‰) and fores…
Origin and dynamics of soil organic matter and vegetation changes during the Holocene in a forest-savanna transition zone, Brazilian Amazon region
Carbon isotope data on soil organic matter (SOM) were collected along an ecosystem transect 90 m in length that includes a tropical forest on the plateau, a transitional forest-savanna and savanna in a depression. Total organic carbon data show a significant increase in carbon content from sites representing forest ecosystem to sites representing savanna ecosystem. It was hypothesized that carbon accumulation in the depression is controlled by fl…
Radiocarbon Dating of Total Soil Organic Matter and Humin Fraction and Its Comparison with 14 C Ages of Fossil Charcoal
During the last decade radiocarbon dating has been used extensively in distinct regions of Brazil to provide information about soil chronology in paleoenvironmental studies. This paper presents 14 C data of soil organic matter (SOM), humin fraction, and charcoal in several soil profiles under natural vegetation from different Brazil locations (north, central, and southeast regions). The main objective is to compare the obtained 14 C dating of tot…
Rapid development of an unusual peat-accumulating ecosystem in the Chilean Altiplano
Stratigraphic relationships, radiocarbon dating, sediment and peat characteristics, and rates of peat and carbon accumulation from a soligenous peatland, or “bofedal,” in the Chilean Altiplano shows the peatland to be unusually young, dynamic, and sensitive to environmental changes. The site lies in the National Park Nevado de Tres Cruces in the puna desert grassland at an elevation of 4300 m a.s.l. Eight peat cores were extracted from a 1.75-km …
Holocene palaeoenvironmental evolution in the São Paulo State (Brazil), based on anthracology and soil δ13C analysis
This paper presents a reconstruction of the Holocene palaeoenvironmental evolution in the central São Paulo State (Brazil) based on anthracological analyses, in association with soil isotopic composition (δ 13 C) and radiocarbon dating from four sites. Anatomical identification of charcoal particles allows the reconstitution of past plant associations, and consequently of the vegetation and climate history. Rather precise interpretations may be a…
Vegetation dynamics during the late Pleistocene in the Barreirinhas region, Maranhão State, northeastern Brazil, based on carbon Isotopes in soil organic matter
The study place is in the Barreirinhas region, Maranhão State, northeastern Brazil. A vegetation transect of 78 km was studied among four vegetation types: Restinga (coastal vegetation), Cerrado (woody savanna), Cerrad"o (dense woody savanna), and Forest, as well as three forested sites around Lagoa do Caçó, located approximately 10 km of the transect. Soil profiles in this transect were sampled for δ 13 C analysis, as well as buried charcoal fra…
Holocene palaeoenvironmental reconstruction in norteastern Brazi inferred from polen,, charcoal and carboon isotope records
Soils in the Barreirinhas region, Maranhao State, were sampled for 613 C analysis and buried charcoal fragments in the soils were radiocarbon dated. Three soil profiles collected in forested areas around the Lagoa do Caqö and one in a woody savanna (mixture of non-arboreal and arboreal species) located approximately 10 km southeast of the Lagoa were studied. A high-resolution pollen record was obtained from lake sediments, showing that forest veg…
The evolution of a tropical rainforest/grassland mosaic in southeastern Brazil since 28,000 14 C yr BP based on carbon isotopes and pollen records
The lack of paleoecological records from the montane Atlantic Rainforest of coastal Brazil, a hotspot of biological diversity, has been a major obstacle to our understanding of the vegetational changes since the last glacial cycle. We present carbon isotope and pollen records to assess the impact of the glaciation on the native vegetation of the Serra do Mar rainforest in São Paulo, Brazil. From ca. 28,000 to ∼ 22,000 14 C yr BP, a subtropical fo…
Geology and Paleoclimatology Research (20 obras) · Environmental Science (17 obras) · Physical geography (17 obras) · Geography (16 obras) · Geology (16 obras) · Radiocarbon dating (14 obras) · Holocene (12 obras) · Total organic carbon (12 obras) · Ecology (11 obras) · Isotope Analysis in Ecology (11 obras)