Methods and code for ‘classical’ age-modelling of radiocarbon sequences

Blaauw, Maarten

doi:10.1016/j.quageo.2010.01.002

Cited by 1,959 publications

(1,644 citation statements)

References 23 publications

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“…We also used the same chronologies for the pollen records as those applied in the LANDCLIM project (Mazier et al 2012;Trondman et al 2015) except for the sites Ekenäs and Skärsgölarna. For those two sites, new age-depth models were established using the computer program clam version 2.1 (Blaauw 2010) that implements the IntCal09 calibration curve of Reimer et al (2009). A smoothing spline was applied for both Ekenäs (four radiocarbon dates ?…”

Section: Time Windows and Chronologiesmentioning

confidence: 99%

Are pollen records from small sites appropriate for REVEALS model-based quantitative reconstructions of past regional vegetation? An empirical test in southern Sweden

Trondman

Gaillard

Sugita

et al. 2015

Veget Hist Archaeobot

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In this paper we test the performance of the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model using pollen records from multiple small sites. We use Holocene pollen records from large and small sites in southern Sweden to identify what is/are the most significant variable(s) affecting the REVEALS-based reconstructions, i.e. type of site (lakes and/or bogs), number of sites, site size, site location in relation to vegetation zones, and/or distance between small sites and large sites. To achieve this objective we grouped the small sites according to (i) the two major modern vegetation zones of the study region, and (ii) the distance between the small sites and large lakes, i.e. small sites within 50, 100, 150, or 200 km of the large lakes. The REVEALS-based reconstructions were performed using 24 pollen taxa. Redundancy analysis was performed on the results from all REVEALS-model runs using the groups within (i) and (ii) separately, and on the results from all runs using the groups within (ii) together. The explanatory power and significance of the variables were identified using forward selection and Monte Carlo permutation tests. The results show that (a) although the REVEALS model was designed for pollen data from large lakes, it also performs well with pollen data from multiple small sites in reconstructing the percentage cover of groups of plant taxa (e.g. open land taxa, summer-green trees, evergreen trees) or individual plant taxa; however, in the case of this study area, the reconstruction of the percentage cover of Calluna vulgaris, Cyperaceae, and Betula may be problematic when using small bogs; (b) standard errors of multiple small-site REVEALS estimates will generally be larger than those obtained using pollen records from large lakes, and they will decrease with increasing size of pollen counts and increasing number of small sites; (c) small lakes are better to use than small bogs if the total number of small sites is low; and (d) the size of small sites and the distance between them do not play a major role, but the distance between the small sites and landscape/vegetation boundaries is a determinant factor for the accuracy of the vegetation reconstructions.

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Section: Time Windows and Chronologiesmentioning

confidence: 99%

Are pollen records from small sites appropriate for REVEALS model-based quantitative reconstructions of past regional vegetation? An empirical test in southern Sweden

Trondman

Gaillard

Sugita

et al. 2015

Veget Hist Archaeobot

View full text Add to dashboard Cite

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“…Ages are presented in calibrated years before present (cal yr BP) where 1950 CE is equal to year 0 cal yr BP. The age-depth models were generated in CLAM (Blaauw, 2010) using smoothing splines (Figure 2). The age model for San Bernardino was created using multiple linear regressions and was not rerun due to the multiple publications already based on the existing chronology (Brunelle et al, 2010 and citations therein).…”

Section: Laboratory and Analyticalmentioning

confidence: 99%

Filling a Geographical Gap: New Paleoecological Reconstructions From the Desert Southwest, USA

et al. 2018

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In 1916 the time stamp for quantitative palynology was set with Lennart von Post's initial paper on pollen analysis and environmental change in the Scandinavian peat bogs. In the 1930s, Von Post provided a map of the known palynological reconstructions. This map showed many conspicuous gaps of geographic coverage that have endured to this day. In particular, environmental reconstruction in arid lands remain much less known, largely due to the paucity of depositional environments in these areas as well as challenges with preservation in regions either uniformly dry or subjected to strong wet/dry phases. Over the last decade we have examined linkages between desert wetland development and episodes of wet and arid conditions. Desert wetland, or ciénegas, are recharged by groundwater and appear to be sensitive to climate-driven groundwater fluctuations. These systems appear to "grow" during wet periods potentially associated with enhanced El Niño activity, suggesting an important linkage with groundwater dynamics and the quantity and frequency of winter precipitation delivery. Hydrologic conditions in ciénegas are also important controls on the preservation of pollen, where episodes of aridity coincide with periods of poor pollen preservation. We assess modern El Niño events, as analogs of past wet conditions, to provide context on the atmospheric controls for delivery of moisture into the desert southwest during winter. Our analysis shows that anomalously high and persistent moisture delivery into the region during El Niño events enables the growth of ciénegas, improves preservation of pollen and promotes the growth of fuels necessary to support wildfire. This paper examines ciénega sites located in the southwestern region of North America at the US/Mexico Border and discusses results that addresses a geographical gap identified by Von Post's original work in paleoenvironmental research.

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“…Radiocarbon ages were calibrated using the IntCal13 data set (Reimer and others 2013) to years before present (cal y BP). Age-depth relationships were established using Clam (Blaauw 2010).…”

Section: Site Locationmentioning

confidence: 99%

Exploring the Ecological History of a Tropical Agroforestry Landscape Using Fossil Pollen and Charcoal Analysis from Four Sites in Western Ghats, India

et al. 2017

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Contrary to expectations, some human-modified landscapes are considered to sustain both human activities and biodiversity over the long-term. Agroforestry systems are among these landscapes where crops are planted under native shade trees. In this context, ancient agroforestry systems can provide insight into how farmers managed the landscape over time. Such insight can help to quantify the extent to which tropical forests (especially habitat-specialist trees) are responding to local and landscape-level management. Here, we extracted fossil pollen (indicator of past vegetation changes) and macroscopic charcoal (indicator of biomass burning) from four forest hollows' sedimentary sequences in an ancient agroforestry system in Western Ghats, India. We used a mixed-modelling approach and a principal components analysis (PCA) to determine past trajectories of forest change and species composition dynamics for the last 900 years. In addition, we reconstructed the long-term forest canopy dynamics and examined the persistence of habitatspecialist trees over time. Our results show that the four sites diverged to a surprising degree in both taxa composition and dynamics. However, despite these differences, forest has persisted over 900 years under agricultural activities within agroforestry systems. This long-term analysis highlights the importance of different land-use legacies as a framework to increase the effectiveness of management across tropical agricultural lands.

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Methods and code for ‘classical’ age-modelling of radiocarbon sequences

Cited by 1,959 publications

References 23 publications

Are pollen records from small sites appropriate for REVEALS model-based quantitative reconstructions of past regional vegetation? An empirical test in southern Sweden

Are pollen records from small sites appropriate for REVEALS model-based quantitative reconstructions of past regional vegetation? An empirical test in southern Sweden

Filling a Geographical Gap: New Paleoecological Reconstructions From the Desert Southwest, USA

Exploring the Ecological History of a Tropical Agroforestry Landscape Using Fossil Pollen and Charcoal Analysis from Four Sites in Western Ghats, India

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