Data from: Tropical Central African bomb radiocarbon reveals antiphase air-mass atmospheric fluxes and vegetation-growth relationships
Data files
Jul 17, 2025 version files 58.38 KB
-
S2_Cameroon_14C_dataset_complete.xlsx
33.13 KB
-
S1_Cameroon_14C_record_weighted_mean.xlsx
16.98 KB
-
README.md
8.28 KB
Abstract
To achieve more accurate Earth system model projections of diverse climate scenarios, researchers need observation-based data on the movement of carbon between reservoirs, and especially across tropical regions. The Tropical Low-Pressure Belt (TLPB) is a key driver of atmospheric circulation across lower latitudes. While the TLPB shifts across the east–west extent of northern Africa, the extent to which 14C concentrations apply to Afrotropical forests remains untested, restricting our understanding about other carbon feedbacks. Here, we present a high-precision atmospheric 14C record (1940–2012) from a lowland tropical tree species (Entandrophragma utile) in Cameroon. We included 107 measurements from whole rings and 15 intra-annual slices. The intra-annual 14C data from 1962, 1963, and 1964 confirm a 7-month long growing season (April–November) with a photosynthetic profile typical of Northern Hemisphere (NH) sites, and showing no nonstructural-carbohydrate interference. The full 14C record reveals that air masses reaching the site were derived primarily from Southern Hemisphere (SH) readings followed by recycled bomb-14C signals from soil and litter. Radiocarbon results were substantiated by HYSPLIT model trajectories coupled with NCEP/NCAR reanalysis data. The paradox of finding that tropical NH trees grow using 14CO2 of SH air masses and land-surface respiration challenges existing zonal 14C classifications. Our findings highlight an essential role for robust observational 14C data in refining atmospheric models and improving carbon-cycle assessments across distinct climate zones.
Data S1 and S2
S1. Cameroon_14C_record_weighted mean
S2. Cameroon_14C_dataset_complete
Brief description of dataset contents
Data file S1 (Cameroon_14C_record_weighted mean) contains the annual data (Weighed mean ± larger of error of the mean or standard error of replicated data, when applicable) of the 73 E. utile tree rings from Cameroon, Africa (1°S, 53°W; 1940–2012). Variables (columns from left to right) listed are described as follows:
- “#” = The sample number.
- “Calendar year AD” = Dendrochronological calendar dates were adjusted to the calendar’s sub-annual level of 0.541 yrs (midpoint of the growing season) based on intra-annual Delta14C values of 1962, 1963 and 1964 rings. See Santos et al. 2025 doi: 10.1016/j.scitotenv.2025.179850 for details on intra-annual calendar year assessment.
- “IRMS-d13C (‰)” = Values of IRMS delta13C were obtained from alpha-cellulose extracts remains. Missing data on cells are indicated by a dash sign to reflect that no remaining cellulose extract was available to provide EA-IRMS data.
- “Age corrected Delta14C (‰)” = decay corrected Delta14C values, expressed in parts per thousand (‰), as described in Santos et al. 2025 doi: 10.1016/j.scitotenv.2025.179850
- “±1s” = 1 sigma or one standard deviation from the measured value.
- “# of 14C measurements” = Total number of 14C measurements pooled into calculation obtained from alpha cellulose extracts produced by using the chemical extraction method described in Santos et al. (2023).
S1 dataset notes
- Cells under IRMS-delta13C with “-“ imply that the measurement was not taken, as no extra alpha cellulose extract was available.
- Radiocarbon results are given as Delta14C corrected for radioactive decay to 1950 and mass-dependent fractionation (Stuiver and Polach 1977). Delta14C corrected weighed mean ± larger of error of the mean or standard error (see data file S2 for details on individual 14C results and errors).
Data file S2 (Cameroon_14C_dataset_complete) contains the complete 14C dataset for the 73 E. utile tree rings from Cameroon, Africa (1°S, 53°W; 1940-2012). A total of 122 radiocarbon results are shown. Variables (columns from left to right) listed are described as follows:
- “# meas.” = number of 14C measurements performed.
- “Radiocarbon AMS facility#” = The assigned numeric entries UCIAMS# corresponds to the 14C-AMS spectrometer identifier of the KCCAMS/UCI facility where samples were measured for their 14C content (6 wheels in total).
- “Sample ID” = Sample ID are the wood-segment (E007C) and calendar year in which ring formation occurs. At Cameroon E. utile tree species growth occurs from April to the end of October of every year. Sample ID’s followed by a, b, c & d letters are the intra-annual 14C signatures spread during the growing season.
- “Year of growth” = Dendrochronological calendar dates were adjusted to the calendar’s sub-annual level of 0.5412 yrs based on intra-annual 14C values of 1962, 1963 and 1964 rings.
- “IRMS-d13C (‰)” = Values of IRMS delta13C were obtained from alpha cellulose extract remains.
- “F14C” = fraction of the modern standard (F14C), following the description in Reimer et al. (2004).
- “±1s” = 1 sigma or one standard deviation from the measured value.
- “Age corrected Delta14C (‰)” = decay corrected Delta14C values, expressed in parts per thousand (‰), as described in Santos et al. 2025 doi: 10.1016/j.scitotenv.2025.179850
- “±1s” = the in per mil representation of the 1 sigma or one standard deviation of the measured value shown in column 7.
- “Weighed Mean Delta14C (‰)” = each Delta14C value per cal. year was multiplied by its assigned weight, summed and divided by the total number of Delta14C values produced.
- “Propagated Error” = square root of the sum of squares.
- “Standard Error” = standard deviation of the sample and “n” is the sample size used.
S2 dataset notes
- Uncertainty between IRMS-delta13C duplicates is in the order of ±0.1‰, and matches with instrumental uncertainty based on measurement of a series of reference materials.
- Cells under IRMS-delta13C with “-“ imply that the measurement was not taken, as no extra alpha cellulose extract was available.
- Cells under “Weighed Mean Delta14C (‰)”, “Propagated Error” and “Standard Error” discriminated by “n/a” imply that just one 14C measurement has been done per calendar year (Year of growth). In other words, there is no other data point to compare it to.
- Radiocarbon results are given as fraction of the modern standard (F14C; Reimer et al. 2004) and Delta14C corrected for radioactive decay to 1950 and mass-dependent fractionation (Stuiver and Polach 1977). Delta14C corrected weighed mean ± larger of error of the mean or standard error.
- Simple pooled standard deviation calculation (by Cohen 1988) based on 26 replicated measurements yielded a precision better than 0.2%.
Mentioned publications in these notes:
Cohen, J. (1988), Statistical Power Analysis for the Behavioral Sciences, 2nd Edition, Hillsdale: Lawrence Erlbaum, 567++, eBook published in 12 May 2013 - New York. DOI: https://doi.org/10.4324/9780203771587
Reimer PJ, Brown TA, Reimer RW. 2004. Discussion: reporting and calibration of postbomb 14C data. Radiocarbon 46(3):1299–1304. DOI: https://doi.org/10.1017/S0033822200033154
Santos, G.M., Komatsu, A.S., Renteria Jr, J.M., Brandes, A.F., Leong, C.A., Collado-Fabbri, S. and De Pol-Holz, R., 2023. A universal approach to alpha-cellulose extraction for radiocarbon analysis of 14C-free to post-bomb ages. Quaternary Geochronology, 74, p.101414. DOI: https://doi.org/10.1016/j.quageo.2022.101414
Santos, G.M., Lucas G. Pereira, L.G., Barbosa, A.C., Ancapichún, S., van der Sleen, P., Zuidema, P.A., Groenendijk, P. 2025. Tropical Central African bomb radiocarbon reveals antiphase air-mass atmospheric fluxes and vegetation-growth relationships. Sci. Total Environ. https://doi.org/10.1016/j.scitotenv.2025.179850
Stuiver M, Polach HA. 1977. Discussion reporting of 14C data. Radiocarbon 19(3):355–363. DOI: https://doi.org/10.1017/S0033822200003672
Description of the data and file structure
Data files S1 and S2 are both Excel sheets. They each contain radiocarbon (14C) and IRMS stable isotope (delta13C) data.
Access information
The dataset shown here has been produced and curated for the purpose of atmospheric 14C reconstructions, and has been thoroughly discussed in Santos et al. 2025 doi: 10.1016/j.scitotenv.2025.179850
Guidaance on use and distribution of these data:
- Researchers are encouraged to use the original data and format shown during analyses. However, we understand that in some applications, specific software and data reformatting may be used. In such cases, or for any assistance with data conversion and analysis, researchers are welcome to contact Guaciara dos Santos (gdossant@uci.edu), who is responsible for the accuracy of this dataset. Dr. Santos is committed to providing support and guidance to facilitate the effective use of this comprehensive dataset in further research and analysis.
- Data citation is encouraged to give credit where credit is due and to help readers to find the original and unaltered material.
Purpose and Utility
- This file is a resource for researchers aiming to conduct detailed analyses of pantropical atmospheric 14C concentrations.
- Offering raw data in this format empowers researchers to draw comparisons to refine the radiocarbon calibration curves, help with tracing carbon sources, and provide a better understanding of long-term global cycle changes.
Dataset funding
This 14C dataset is a result of an US National Science Foundation fund granted to Dr. Guaciara dos Santos (AGS-1903690).