δ13C variation of soil organic matter as an indicator of vegetation change during the Holocene in central Cameroon

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. 14C data from charcoal, soil organic matter (SOM) and its component humin fraction indicate that the organic matter in the studied soils is essentially Holocene in origin. 13C data indicate that C3 type plants were the dominant vegetation at all study areas in the early Holocene, and during the entire Holocene, in the forest sites of Central Rondônia state and in the forest site 50 km from the city of Humaitá. 13C data also indicate that C4 plants have influenced significantly the vegetation at the transitional forest and the Cerrado (wooded savanna) sites of Southern Rondônia state and the forest ecosystem located 20 km from the Humaitá city. These typical C4 type isotopic signatures probably reflect a drier climate during the mid-Holocene. The 13C records representing probably the last 3000 yr show an expansion of the forest, due to a climatic improvement, in areas previously occupied by savanna vegetation. These results and other published data for the Amazon region indicate that the areas representing today's forest-savanna boundaries have been determined by significant vegetation changes during the Holocene. The boundary between forest and savanna vegetation seems to be quite sensitive to climatic change and should be the focus of more extensive research to correlate climate and past vegetation dynamics in the Amazon region.

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Thermal stability of soil organic matter pools and their δ13C values after C3–C4 vegetation change

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2006.12.025 ◽

2007 ◽

Vol 39 (5) ◽

pp. 1173-1180 ◽

Cited By ~ 23

Author(s):

Maxim Dorodnikov ◽

Andreas Fangmeier ◽

Yakov Kuzyakov

Keyword(s):

Thermal Stability ◽

Organic Matter ◽

Soil Organic Matter ◽

Vegetation Change ◽

Δ13c Values ◽

Thermal Stability Of

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The origin of the forest-grassland mosaic of central Cameroon: What we learn from the isotopic geochemistry of soil organic matter

The Holocene ◽

10.1177/0959683620932963 ◽

2020 ◽

Vol 30 (10) ◽

pp. 1391-1399

Author(s):

Thierry Desjardins ◽

Bruno Turcq ◽

Anne-Marie Lézine ◽

Jean-Pierre Nguetnkam ◽

Magloire Mandeng-Yogo ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Large Scale ◽

Forest Cover ◽

Central Africa ◽

Environmental Crisis ◽

Forest Expansion ◽

The Holocene ◽

Forest Sites ◽

Forest Mosaic

The end of the Holocene Humid Period was characterized by the massive collapse of forest ecosystems in central Africa. Was this large-scale environmental crisis dated between 3300 and 2500 years BP at the origin of the present-day wooded-grassland/forest mosaic of central Cameroon? Here we present carbon isotope data on soil organic matter collected from 29 sites from this area, including the Grassfield plateaus, with the aim of characterizing this environmental crisis and discussing the origin of the present-day landscape. 14C data on total soil organic matter and charcoal fragments show that the organic matter in these soils originates from the Holocene. In our forest sites, the δ13C profiles do not show any marked alteration of the forest cover throughout the Holocene. Discrete traces of forest expansion or retreat are observed only punctually at the forest margins. In the wooded-grassland/forest mosaic zone, the environmental crisis was of reduced amplitude. In the present grassland and wooded grassland areas, there was no true forest during the lower to middle Holocene, but a markedly more tree-covered landscape. The timing of this crisis revealed by our 14C measurements, although only indicative at this stage, suggests that it occurred earlier at higher altitudes than in the lowlands due to marked topographic relief favoring drainage along the slopes. These results fit a climatic rather than anthropogenic origin of the vegetation opening in this region.

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Assessment of vegetation change and landscape variability by using stable carbon isotopes of soil organic matter

Australian Journal of Botany ◽

10.1071/bt04124 ◽

2005 ◽

Vol 53 (7) ◽

pp. 651 ◽

Cited By ~ 21

Author(s):

Evelyn G. Krull ◽

Steven S. Bray

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Vegetation Change ◽

Stable Carbon Isotopes ◽

Vegetation History ◽

Statistical Significance ◽

Aerial Photographs ◽

Stable Carbon ◽

Carbon Isotopic ◽

Landscape Variability

Stable carbon isotopic (δ13C) analyses of soil organic matter (SOM) have been used in the past to characterise C3–C4 vegetation changes. However, the temporal and spatial resolution of these isotopic data are not well established. Here, we present data from δ13C analyses of whole and size-separated SOM, which are discussed in conjunction with organic (total organic carbon (TOC) content) and inorganic (%clay) soil data. These data are put into context with the current vegetation state (assessed from tree size-class distribution) and the 50-year vegetation history (assessed from aerial photographs). By linking below- and above-ground datasets, we show that δ13C analyses of SOM can accurately record vegetation-change histories over short- (10 and 50years) and longer-term (hundreds of years) time scales. Our data also show that spatial variability was relatively small for the clay TOC content but was much larger for δ13C data, indicating that the number of soil cores required for statistical significance is highly dependent on the kind of measurements intended. Finally, interpretation of δ13C data from SOM to assess the history of C3–C4 vegetation change is complicated by the inherent 13C-enrichment of SOM, owing to decomposition processes, which occurs regardless of vegetation change. We suggest a method for distinguishing 13C-enrichment of SOM that is due to soil-inherent (decomposition-related) processes from 13C-enrichment that is due to increased inputs of C4 organic matter.

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Natural Radiocarbon Measurements in Brazilian Soils Developed on Basic Rocks

Radiocarbon ◽

10.1017/s0033822200017574 ◽

1996 ◽

Vol 38 (2) ◽

pp. 203-208 ◽

Cited By ~ 40

Author(s):

L. C. R. Pessenda ◽

E. P. E. Valencia ◽

P. B. Camargo ◽

E. C. C. Telles ◽

L. A. Martinelli ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Climate Changes ◽

Soil Profiles ◽

Vegetation Changes ◽

The Holocene ◽

Native Forests ◽

Subtropical Soils ◽

Brazilian Soils ◽

Basic Rocks

This paper presents 14C, 13C 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. 14C data from SOM indicate that the organic matter in the soils studied is of at least Holocene age. 13C data indicate that C4 plants probably provided the dominant vegetation in Londrina and Piracicaba during the early and mid-Holocene and that C3 plants provided the dominant vegetation in the Altamira region during the Holocene.

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Soils in Karst Sinkholes Record the Holocene History of Local Forest Fires at the North of European Russia

Forests ◽

10.3390/f11121268 ◽

2020 ◽

Vol 11 (12) ◽

pp. 1268

Author(s):

Nikita Mergelov ◽

Dmitry Petrov ◽

Elya Zazovskaya ◽

Andrey Dolgikh ◽

Alexandra Golyeva ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Forest Fires ◽

Soil Formation ◽

Soil Morphology ◽

Deep Soil ◽

Radiocarbon Dates ◽

The Holocene ◽

The North ◽

Peat Deposits

Despite the abundance of charcoal material entrapped in soils, they remain relatively less studied pyrogenic archives in comparison to the sedimentary paleofire records (e.g., lacustrine and peat deposits), and that is especially the case in most of Russia’s territory. We report here on the deep soil archives of the Holocene forest fires from the Pinega District of the Arkhangelsk region (64.747° N, 43.387° E). Series of buried soil profiles separated by charcoal layers and clusters were revealed in specific geomorphological traps represented by the active and paleokarst subsidence sinkholes on sulfate rocks overlaid by glacial and fluvial deposits. We combine the study of soil morphology and stratigraphy with a set of radiocarbon data on charcoal and soil organic matter, as well as the anthracomass analysis, to extract a set of paleoenvironmental data. A total of 45 radiocarbon dates were obtained for the macrocharcoal material and the soil organic matter. The maximum temporal “depth” of archives estimated from the radiocarbon dating of macrocharcoal reached 10,260 ± 35 cal yr BP. Soil formation with Podzols established at the inter-pyrogenic stages repeatedly reproduced within the period of ten thousand years, while the dominant tree species was Pinus sp. According to the macrocharcoal data, the intervals between fires have shortened in the last thousand years. Dendrochronological estimates suggest the occurrence of fires in almost every decade of the 20th and early 21st centuries. This is the first study of the millennia-scale soil record of forest fires in this particular region of Russia.

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