Sampling plants and malacofauna in 87Sr/86Sr bioavailability studies: Implications for isoscape mapping and reconstructing of past mobility patterns

Establishing strontium isotope (87Sr/86Sr) geographical variability is a key component of any study that seeks to utilize strontium isotopes as tracers of provenance or mobility. Although lithological maps can provide a guideline, estimations of bioavailable 87Sr/86Sr are often necessary, both in qualitative estimates of local strontium isotope “catchments” and for informing/refining isoscape models. Local soils, plants and/or animal remains are commonly included in bioavailability studies, although consensus on what (and how extensively) to sample is lacking. In this study, 96 biological samples (plants and snails) were collected at 17 locations spanning 6 lithological units, within a region of south-west France and an area with a high concentration of Paleolithic archaeological sites. Sampling sites aligned with those from a previous study on soil bioavailable strontium, and comparison with these values, and the influence of environmental and anthropogenic variables, was explored. Data confirm a broad correspondence of plant and snail 87Sr/86Sr values with lithological unit/soil values, although the correlation between expected 87Sr/86Sr values from lithology and bioavailable 87Sr/86Sr ratios from biological samples was higher for plants than for snails. Grass, shrub and tree 87Sr/86Sr values were similar but grasses had a stronger relationship with topsoil values than trees, reflecting differences in root architecture. Variability in 87Sr/86Sr ratios from all plant samples was lower for sites located on homogeneous geological substrates than for those on heterogeneous substrates, such as granite. Among environmental and anthropogenic variables, only an effect of proximity to water was detected, with increased 87Sr/86Sr values in plants from sites close to rivers originating from radiogenic bedrock. The results highlight the importance of analyzing biological samples to complement, inform and refine strontium isoscape models. The sampling of plants rather than snails is recommended, including plants of varying root depth, and (if sample size is a limitation) to collect a greater number of samples fromareas with heterogeneous geological substrates to improve the characterizations of those regions. Finally, we call for new experimental studies on the mineralized tissues of grazers, browsers, frugivores and/or tree leaf feeders to explore the influence of 87Sr/86Sr variability with soil profile/root architecture on 87Sr/86Sr values of locally-feeding fauna.

Investigating Cattle Procurement at Great Zimbabwe Using 87Sr/86Sr

At the ancient Shona centre of Great Zimbabwe (1200–1700 CE), cattle (Bos taurus) were centrally important for economic, social, and symbolic purposes. 87Sr/86Sr for modern plants collected in southern Zimbabwe vary from 0.7054 to 0.8780 and ranges differ between some geological substrates. 87Sr/86Sr in serial samples of Bos taurus tooth enamel provides information on where animals consumed at Great Zimbabwe were raised and how herds were managed. The majority of animals sampled were born and remained for their first year of life in a region some 40–120 km south of Great Zimbabwe. Few animals came from geological substrates like that of Great Zimbabwe itself, and none from areas underlain by basalts (> 120 km south of Great Zimbabwe). Earlier hypotheses of transhumance are not supported. These findings will help to build a fuller picture of the role of local commodities (in this case, cattle) in the economic networks that supported the rise and florescence of Great Zimbabwe as a major centre of power.

On the role of parent material for predictive mapping of soil properties in mountain forests

<p>Parent material is widely recognised as an important factor for soil formation. Thus, quantitative information on the lithogenetic, geochemical, and physical characteristics of the subsolum geological substrates (SSGS) are essential input parameters for digital soil mapping (DSM). Forming the interface between bedrock – the domain of geologists, and soil – the domain of soil scientists, spatial information on SSGS is however scarce. Recognising these shortcomings, a novel geochemical-physical classification system for subsolum geological substrates has been developed, in order to support DSM at a regional scale. The units of the classification system reflect the properties of the SSGS also considering multilayering structure of quaternary deposits. The basis for the classification are mineral component groups, namely dolomite, calcite, and felsic, mafic, and clay minerals. In order to test the relevance of SSGS for the prediction of spatially continuous physical and chemical soil properties, Generalized Additive Models (GAMs) were applied to the forested area of Tyrol, Austria. The plant-available water storage capacity, as a physical soil property, was predicted with r² = 0.56. The Ellenberg´s mean soil reaction indicator value for vegetation turned out to be a suitable proxy for soil pH value and was predicted with r² = 0.75. Topography and associated morphometric terrain features are formative characteristics of mountain areas and, due to its various effects on redistribution processes as well as on water and energy budget of forest sites, are considered as the most essential soil forming factors. Thus, variables derived from digital terrain models, which are available in high spatial resolution, are assumed to be one of the most important predictors for digital soil mapping. In our study we could show however, that SSGS information is the most relevant predictor for both investigated soil properties. In the plant-available water storage capacity model, the predictor variables related to SSGS account for around 76% of the variance explained. Accordingly, a special focus should be placed on the predictive relevance of parent material and the frequently unlocked potential of quantitative geological substrate information. Thus, the newly developed subsolum geological substrate information could stimulate further developments in digital soil mapping, especially in mountain environments.</p>

Spatial vegetation distribution and zonal vegetation type on islands in southern part of the Lena Delta (Eastern Siberia)

In this research spatial distribution of the different vegetation types on Lena Delta islands described in connection with their relief, time of formation and geological substrates. It was shown that zonal vegetation can be find only on third river terrace on gentle slopes. Because of continuous permafrost predominant vegetation is presented by hydro serial communities united into successional cycles. Zonal vegetation types occupy not more than 1-2% of the whole area.

Sampling Plants and Malacofauna in 87Sr/86Sr Bioavailability Studies: Implications for Isoscape Mapping and Reconstructing of Past Mobility Patterns

Establishing strontium isotope (87Sr/86Sr) geographical variability is a key component of any study that seeks to utilize strontium isotopes as tracers of provenance or mobility. Although lithological maps can provide a guideline, estimations of bioavailable 87Sr/86Sr are often necessary, both in qualitative estimates of local strontium isotope “catchments” and for informing/refining isoscape models. Local soils, plants and/or animal remains are commonly included in bioavailability studies, although consensus on what (and how extensively) to sample is lacking. In this study, 96 biological samples (plants and snails) were collected at 17 locations spanning 6 lithological units, within a region of south-west France and an area with a high concentration of Paleolithic archaeological sites. Sampling sites aligned with those from a previous study on soil bioavailable strontium, and comparison with these values, and the influence of environmental and anthropogenic variables, was explored. Data confirm a broad correspondence of plant and snail 87Sr/86Sr values with lithological unit/soil values, although the correlation between expected 87Sr/86Sr values from lithology and bioavailable 87Sr/86Sr ratios from biological samples was higher for plants than for snails. Grass, shrub and tree 87Sr/86Sr values were similar but grasses had a stronger relationship with topsoil values than trees, reflecting differences in root architecture. Variability in 87Sr/86Sr ratios from all plant samples was lower for sites located on homogeneous geological substrates than for those on heterogeneous substrates, such as granite. Among environmental and anthropogenic variables, only an effect of proximity to water was detected, with increased 87Sr/86Sr values in plants from sites close to rivers originating from radiogenic bedrock. The results highlight the importance of analyzing biological samples to complement, inform and refine strontium isoscape models. The sampling of plants rather than snails is recommended, including plants of varying root depth, and (if sample size is a limitation) to collect a greater number of samples from areas with heterogeneous geological substrates to improve the characterizations of those regions. Finally, we call for new experimental studies on the mineralized tissues of grazers, browsers, frugivores and/or tree leaf feeders to explore the influence of 87Sr/86Sr variability with soil profile/root architecture on 87Sr/86Sr values of locally-feeding fauna.

Subglacial hydrological control on flow of an Antarctic Peninsula palaeo-ice stream

Basal hydrological systems play an important role in controlling the dynamic behaviour of ice streams. Data showing their morphology and relationship to geological substrates beneath modern ice streams are, however, sparse and difficult to collect. We present new multibeam bathymetry data that make the Anvers-Hugo Trough (AHT) west of the Antarctic Peninsula the most completely surveyed palaeo-ice stream pathways in Antarctica. We interpret landforms as indicating that subglacial water availability played an important role in facilitating ice stream flow and controlling shear margin positions. Water was likely supplied to the ice stream bed episodically as a result of outbursts from a subglacial lake located in the Palmer Deep basin on the inner continental shelf. These interpretations have implications for controls on the onset of fast ice flow, the dynamic behaviour of palaeo-ice streams on the Antarctic continental shelf, and potentially also for behaviour of modern ice streams.