Opal Phytoliths Research Articles

Inter- and intra-observer variation in phytolith morphometry.

Archaeobotanists and palaeoecologists extensively use geometric morphometrics to identify plant opal phytoliths. Particularly when applied to assemblages of phytoliths from concentrations retrieved from closed contexts, morphometric data from archaeological phytoliths compared with similar data from reference material may allow taxonomic attribution. Observer variation is one aspect of phytolith morphometry that has received little attention but may be an important source of error, and hence cause of potential misidentification of plant remains. To investigate inter- and intra-observer variation in phytolith morphometry, eight researchers (observers) from different laboratories measured 50 samples each from three phytolith morphotypes, Bilobate, Bulliform flabellate and Elongate dendritic, three times, under the auspices of the International Committee for Phytolith Morphometrics (ICPM). Data for 17 size and shape variables were collected for each phytolith by manually digitising a phytolith outline (mask) from a photograph, followed by measurement of the mask with open-source morphometric software. Inter-observer variation ranged from 0 to 23% difference from the mean of all observers. Intra-observer variation ranged from 0 to 9% difference from the mean of individual observers per week. Inter- and intra-observer variation was generally higher among inexperienced researchers. Scaling errors were a major cause of variation and occurred more with less experienced researchers, which is likely related to familiarity with data collection. The results indicate that inter- and intra-observer variation can be substantially reduced by providing clear instructions for and training with the equipment, photo capturing, software, data collection and data cleaning. In this paper, the ICPM provides recommendations to minimise variation.Advances in automatic data collection may eventually reduce inter- and intra-observer variation, but until this is common practice, the ICPM recommends that phytolith morphometric analyses adhere to standardised guidelines to assure that measured phytolith variables are accurate, consistent and comparable between different researchers and laboratories.

Luminescence and thermometry studies of plant opal phytoliths

We have investigated the luminescence properties of plant opal phytoliths to assess their suitability for determination of age and/or thermometric information from soil and sediment sequences. This study examined a <2.37 gcm−3 density fraction in parallel with quartz grains from samples collected from alluvial terraces. We observed comparable optically stimulated luminescence (OSL) from the phytolith fraction to the quartz, and thermoluminescence (TL) with broader peaks and continuum to higher temperatures. Scanning electron microscopy (SEM) data suggested the presence of opal clasts and contaminant minerals. To better understand the luminescence from opal phytoliths we analyzed a suite of biogenic materials including very pure diatoms, phytoliths, and quartz reference materials. We observe low sensitivity but measurable OSL signals in all the materials analyzed, and infrared stimulated luminescence (IRSL) signals with fast decay rates exceeding those of more typical feldspars in some of the purer materials. TL signals are similar to those observed for glasses and suggests dose response might extend beyond quartz saturation levels. Preliminary investigations of OSL dose response show very promising growth characteristics for opal phytolith samples and all other biogenic silica materials analyzed.

Tracing the biographies of textiles in the transition of medieval to modern times: Wool fabrics and brigandines from an Iberian castle

Findings of archaeological textiles and fibres in Northern Iberia are extremely rare. The occurrence of a set of textile fragments, dated between the 14th and 16th centuries CE at the Pambre castle (Palas de Rei, Lugo, Spain) is exceptional. The original stone roof of the southeastern tower was intact. The dark, cold and moist conditions inside the tower favoured the preservation of a unique series of waterlogged textile remains. In addition, a set of pseudomorphs preserved by mineral replacement were recovered from the east edge of the north wing in the main hall of the castle. Fibres have been identified using optical and scanning electron microscopy (SEM), and they have been chemically characterised using Energy Dispersive X-Ray Spectroscopy (EDX). We also performed analytical pyrolysis-GC-MS (Py-GC-MS) and thermally assisted hydrolysis and methylation (THM-GC-MS) of the wool fabrics and pseudomorphs to assess their state of degradation and the presence of chemical markers associated to the use of these textile remains. High performance liquid chromatography with diode array detection (HPLC-DAD-MS) and ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS/MS) analysis were applied on wool fabrics to identify the chemical markers of dyes but without success. To expand the information related to raw material identification and the technical aspects of the fabrics, further evidence such as adherences identified as opal phytoliths, seeds, and insect remains associated to wool fabrics were examined. These findings offer a unique glimpse into the clothing dated to the end of the Medieval period, and its life-cycle. Wool scraps were probably part of at least two different garments, whereas the mineralised textiles probably formed part of at least two brigandines which were made of bast fibres, flax, or hemp.

Extinct Eurasian rhinoceros Coelodonta and Stephanorhinus dental pathologies and tooth change modus

Dental pathologies are described for four extinct rhinoceroses Coelodonta antiquitatis (Blumenbach, 1799) and Stephanorhinus hemitoechus (Falconer, 1868) of the Late Pleistocene Weichselian Glacial (MIS 3-5 d), Stephanorhinus kirchbergensis Jäger, 1839 of the Late Pleistocene Eemian Interglacial (MIS 5e), and Stephanorhinus hundsheimensis (Toula, 1902) from the Middle Pleistocene Cromerian Mosbach Interglacial (MIS 11) which material is mainly from the Rhine Valley megafauna migratory channel of Central Europe. All three extinct and even extant rhinoceros share similar ontogenetic P4 pathologic misplacement pathologies. Those caused in some cases further dental abnormalities impacting the lower jaw dentition, even in rare cases including complete deformation of the lower jaw. In the browsing Stephanorhinus (S. kirchbergensis, S. hundsheimensis) the P4 is more commonly misplaced; in the Mid-Pleistocene Mosbach S. hundsheimensis are three examples with similar misplacements on the right and left maxillaries, which have a similar genetic pool background of a local palaeopopulation. The grazer rhinoceros C. antiquitatis has a further pathology type with loss or even genetically pre-assessed non-development of the first upper or lower PM premolars or last M molars. The strong wear, damage, and loss of the anterior premolars in elderly individuals as ontogenetically based pathology, seem to result from intensive grazer and opal phytoliths abrasion. This loss finally resulted in irregularities of the permanent dentition and influenced wear stages and irregular abrasion angles of the tooth rows, affecting the upper and lower rows each others.

Phytoliths from some grasses (Poaceae) in arid lands of Xinjiang, China

Opal phytoliths, as silicon dioxide inclusions, are abundant in different parts of a plant. It is known that grasses are the most representative in this respect. The research of phytoliths, removed from 25 most common grass species in the arid and semiarid lands of the Junggar Basin and adjacent areas, has been undertaken. The visual estimation of diversity and variability of silica cells and identification of their morphological types (patterns) were also the aim of our research. Since the work is preliminary, we have emphasized on the visual estimation of silica cell variability and involved only the leaf blades in the analysis. Drawings of the revealed silica cells, characteristic of 25 species, are provided. The sig-nificant morphological diversity of phytoliths has been revealed, as well as their taxonomic similarity at the level of subfamilies. These data can be used for the identification of phytoliths from sediments.

Phytolith and Calcitic Spherulite Indicators from Modern Reference Animal Dung from Mediterranean Island Ecosystems: Menorca, Balearic Islands

This study illustrates the contribution of plant and faecal microfossil records to interdisciplinary approaches on the identification, composition, taphonomy and seasonality of livestock dung materials. The focus is on the taphonomy of opal phytoliths and calcitic dung spherulites embedded within modern faecal pellets collected from pasture grounds and pens from a range of animals, including cattle, sheep and pigs from three different farms and seasons of the year in Menorca (Balearic Islands, Spain) declared a Biosphere Reserve by UNESCO. Modern reference materials provide comparative plant and dung microfossil indicators on factors affecting the formation, composition, preservation and decay of animal faeces, as well as on the diverse environmental and anthropogenic aspects influencing these. The reported results show relevant changes in phytolith and spherulite composition according to animal species and age, livestock management, seasonality, and grazing and foddering regimes. Both microfossil records provide fundamental information on taphonomic issues that are understudied, such as the variation in the digestibility among different species, including under investigated animals such as pigs, as well on the seasonality of plant and faecal microfossils that are excreted with dung as an important material for reconstructing human-environment interactions which is commonly overlooked in archaeology.

Diverse evidence for grasslands since the Eocene in Patagonia

Timing and ecological steps of the rise and expansion of grasslands differ not only geographically but also according to the type of available information. Patagonia (Argentina) was largely considered the region where grasslands and grazers early evolved in the Eocene, mostly based on functional morphology of mammals. However, recent paleobotanical studies question this traditional view and maintain that this occurred after early Miocene. To tackle this discrepancy, we conduct a multidisciplinary and integrative approach using diverse lines of evidence obtained from middle Eocene - middle Miocene tuffaceous deposits of central and northern Patagonia. Gathered data correspond to sedimentary facies, paleosols, insect trace fossils, opal phytoliths and fossil mammals (tooth morphology, body size). Long-lasting and frequent volcanic ashfalls caused permanent disturbances in physical scenarios, biotic systems and grassy habitats; just like herbivory of mammals through coevolutionary grass-grazer mechanisms. The results indicate that soils, vegetation, insects and mammal herbivores begun synchronously to record diverse traits related to grasslands showing mosaic vegetation since middle Eocene (~44 Ma). These traits include mollic paleosols, abundant and persistent dung beetle trace fossils (Coprinisphaera ichnofacies), phytolith assemblages attributable to savannas and medium to large-size hypsodont mammals. We also track the evolutionary history after the reduction of closed forests, recognizing alternating subhumid savannas with riparian forests, where the relative frequency between grasses, palms, trees and shrubs fluctuated in time and space; and desert vegetation (shrublands) dominated by palms and shrubs during dryer periods. The advent and expansion of grasslands can be linked to the cooling and drying period subsequent to the Early Eocene Climate Optimum.

A new perspective of the Alboran Upwelling System reconstruction during the Marine Isotope Stage 11: A high-resolution coccolithophore record

A high-resolution study of the MIS 12/MIS 11 transition and the MIS 11 (430–376 kyr) coccolithophore assemblages at Ocean Drilling Program Site 977 was conducted to reconstruct the palaeoceanographic and climatic changes in the Alboran Sea from the variability in surface water conditions. The nannofossil record was integrated with the planktonic oxygen and carbon stable isotopes, as well as the Uk'37 Sea Surface Temperature (SST) at the studied site during the investigated interval. The coccolithophore primary productivity, reconstructed from the PPP (primary productivity proxy = absolute values of Gephyrocapsa caribbeanica + small Gephyrocapsa group) revealed pronounced fluctuations, that were strongly associated with variations in the intensity of the regional Alboran Upwelling System. The comparison of the nannoplankton record with opal phytolith content for the studied site and the already available pollen record at the nearby Integrated Ocean Drilling Program Site U1385, suggests an association of the upwelling dynamics with the variability of the North Atlantic Oscillation-like (NAO-like) phase. High PPP during positive (+) NAO-like phases is the result of intensified upwelling, owing to the complete development of the surface hydrological structures at the Alboran Sea. This scenario was identified during the MIS 12/MIS 11 transition (428-422 kyr), the late MIS 11c (405-397 kyr), and MIS11 b to MIS 11a (397-376 kyr). Two short-term minima in the PPP and SST were observed during MIS 11 b and were coeval with the North Atlantic Heinrich-type (Ht) events Ht3 (∼390 kyr) and Ht2 (∼384 kyr). Increased abundance of the subpolar Coccolithus pelagicus subsp. pelagicus and Gephyrocapsa muellerae was consistent with the inflow of cold surface waters into the Mediterranean Sea during the Ht events. Lowered PPP during negative (−) NAO-like phases is the result of moderate upwelling by the incomplete development of surface hydrological structures at the Alboran Sea. This scenario is expressed during the early MIS 11c (422-405 kyr). Overall, the results of our study provide evidence of the important role of atmospheric circulation patterns in the North Atlantic region for controlling phytoplankton primary production and oceanographic circulation dynamics in the Western Mediterranean during MIS 11.

Diversity of silicon release rates among tropical tree species during leaf-litter decomposition

Leaf-litter is a significant source of biogenic Si, and differences among tree species in Si release rates during litter decomposition are important for quantifying Si cycles in forest ecosystems. We conducted two experiments to improve mechanistic understanding of Si release rates from dead leaves, using lowland tropical trees of Sarawak, Borneo. In the first experiment, we assessed Si leaching from leaf litter when they were shaken in water for four hours. In the second experiment, leaf litter samples were allowed to decompose in mesh bags in growth chambers for two months, in order to determine rates of decomposition and Si release, and to explore a relationship between decomposition rate and initial litter chemistry. Among the 12 species with large differences in initial leaf-litter Si concentration (0.72–80.0 mg Si g−1), Si leaching to water varied widely (0.04–0.16 mg Si g−1) and positively correlated with the initial Si concentration (R2 = 0.87; P < 0.001). Si release per unit leaf dry weight in the decomposition experiment was also positively correlated with initial litter Si concentration among six species (R2 = 0.998; P < 0.001). In contrast, proportion of initial Si content released did not exhibit a significant relationship with their decomposition rates, which were correlated with labile carbon content in leaf litter (e.g. hemicellulose). Our results suggest that Si release rates from decomposing leaf litter cannot be simply predicted from decomposition rates. The species differences in locations and stability of opal phytoliths and their resulting effects on Si dissolution rates should be considered.

Late Pleistocene and Late Holocene environment and climate in the campos region of southeastern South America inferred from phytolith, diatom and geochemical data

A paleolimnological study was undertaken for a sediment core from Laguna Formosa, a subtropical lake in the northern campos inland region of Uruguay. The record encompasses a Late Pleistocene and Late Holocene interval, interrupted by a hiatus. We analyzed (1) opal phytoliths and diatoms to infer the regional environment, climate, and changes in lake trophic state, and (2) total carbon and nitrogen (TC and TN) and stable isotope data (δ13C and δ15N) to infer organic matter sources and composition. Findings indicate that, in Late Pleistocene times, a cool, semi-arid or highly seasonal climate existed, with a dominance of C3 grasslands and riparian hydrophilous shrublands while the shallow freshwater environment was characterized by benthic diatoms and littoral macrophytes. Late Holocene times were initially characterized by a temperate and humid or sub-humid climate, and dominance of grasslands and bunch grasses, while Laguna Formosa was dominated by phytoplankton. The abundance and diversity of littoral hydrophilic vegetation, and riparian forest vegetation, increased progressively over time, as a result of increased rainfall, from ca. 1800 cal yr BP and the onset of a subtropical (temperate and humid) climate by ca. 1300 cal yr BP. Such inferences are in close agreement with an earlier palynological study of Laguna Formosa, and support the paleoclimatic models for the Late Pleistocene and Late Holocene of southeastern South America.

International Code for Phytolith Nomenclature (ICPN) 2.0.

Opal phytoliths (microscopic silica bodies produced in and between the cells of many plants) are a very resilient, often preserved type of plant microfossil. With the exponentially growing number of phytolith studies, standardization of phytolith morphotype names and description is essential. As a first effort in standardization, the International Code for Phytolith Nomenclature 1.0 was published by the ICPN Working Group in Annals of Botany in 2005. A decade of use of the code has prompted the need to revise, update, expand and improve it. ICPN 2.0 formulates the principles recommended for naming and describing phytolith morphotypes. According to these principles, it presents the revised names, diagnosis, images and drawings of the morphotypes that were included in ICPN 1.0, plus three others. These 19 morphotypes are those most commonly encountered in phytolith assemblages from modern and fossil soils, sediments and archaeological deposits. An illustrated glossary of common terms for description is also provided.

Paleovegetational reconstruction from fossil opal phytolith assemblages in the soil of tropical seasonal forests in Thailand

Paleovegetational reconstruction from fossil opal phytolith assemblages in the soil of tropical seasonal forests in Thailand

Visibility, Preservation and Colour: A Descriptive System for the Study of Opal Phytoliths in (Archaeological) Soil and Sediment Thin Sections

ABSTRACTPhytoliths are abundantly reported in (archaeological) soil thin sections. However, standard description systems are largely missing. The purpose of this paper is to present a descriptive system describing three aspects of phytoliths in soil thin sections: visibility, preservation and colour (VPC). The visibility expresses to which extent the phytoliths are masked or surrounded by fine material. The preservation is an indicator for the physico-chemical alterations that affected the phytoliths. Finally, colour is an indicator of the charring of the organic material surrounding the phytoliths.

岩手山麓における最近13,000年間の火山灰土壌の植生環境 : 分火山灰層の植物珪酸体分析

岩手山麓における最近13,000年間の火山灰土壌の植生環境 : 分火山灰層の植物珪酸体分析

Nano-indentation of native phytoliths and dental tissues: implications for herbivore-plant combat and dental wear proxies

Tooth wear induced by abrasive particles is a key process affecting dental function and life expectancy in mammals. Abrasive particles may be plant endogenous opal phytoliths, exogene wind-blown quartz dust or rain borne mineral particles ingested by mammals. Nano-indentation hardness of abrasive particles and dental tissues is a significant yet not fully established parameter of this tribological system. We provide consistent nano-indentation hardness data for some of the major antagonists in the dental tribosystem (tooth enamel, tooth dentine and opaline phytoliths from silica controlled cultivation). All indentation data were gathered from native tissues under stable and controlled conditions and thus maximize comparability to natural systems. Here we show that native (hydrated) wild boar enamel exceeds any hardness measures known for dry herbivore tooth enamel by at least 3 GPa. The native tooth enamel is not necessarily softer then environmental quartz grit, although there is little overlap. The native hardness of the tooth enamel exceeds that of any silica phytolith hardness recently published. Further, we find that native reed phytoliths equal native suine dentine in hardness, but does not exceed native suine enamel. We also find that native suine enamel is significantly harder than dry enamel and dry phytoliths are harder than native phytoliths. Our data challenge the claim that the culprit of tooth wear may be the food we chew, but suggest instead that wear may relates more to exogenous than endogenous abrasives.

Taxonomic assessment of opal phytoliths from grasses of deltaic West Bengal, India

In the present study, taxonomic potential of opal phytoliths was examined in grasses from lower Gangetic delta, West Bengal, India. The study revealed that finer classification of phytoliths can increase the efficacy of opal silica as taxonomic proxy by minimizing the influences of multiplicity and redundancy. We isolated 187 phytolith sub‐morphotypes, categorized under 10 major groups, from 110 grass species belonging to 45 genera, 21 sub‐tribes, 13 tribes and 7 subfamilies. Cluster and correspondence analyses showed that all the significantly represented subfamilies can be clearly distinguished on the basis of either principal morphotypes or sub‐morphotypes. However, genus/species level discrimination may only be possible by deploying phytolith based identification key developed by utilizing detailed grass phytolith micro‐morphometry and frequency attributes. We conclude that grass phytolith characteristics provide useful and significant information for distinguishing grass taxa of deltaic West Bengal.

植物ケイ酸体による放牧家畜の採食草種の判定と採食量の推定 : 1.植物ケイ酸体による草種判定の可能性と生育段階によるケイ酸体構成割合の変化

植物ケイ酸体による放牧家畜の採食草種の判定と採食量の推定 : 1.植物ケイ酸体による草種判定の可能性と生育段階によるケイ酸体構成割合の変化

African savanna elephants and their vegetation associations in the Cape Region, South Africa: Opal phytoliths from dental calculus on prehistoric, historic and reserve elephants

This study tests the association between opal phytoliths in dental calculus on modern, historic, and prehistoric specimens of Loxodonta africana (African savanna elephant) with their local and regional vegetation. The modern samples were obtained from dental remains from deceased animals at the Addo Elephant National Park (Eastern Cape Province) and the Pilanesberg National Park & Game Reserve (Northwest Province) in the Republic of South Africa. The historic and prehistoric specimens, presumed to be free-roaming elephants, were sampled from museum collections in the Eastern Cape and Western Cape Provinces. In addition to comparing phytolith assemblages in dental calculus with those of the main vegetation associations, this study assesses the phytolith assemblage differences between free-roaming and park elephants.The results show that: (1) the phytolith assemblages in dental calculus of park elephants show little variation among individual specimens and close resemblance to phytolith assemblages of soils inside their areas of confinement; (2) the free-roaming specimens have a much higher diversity of phytolith morphotypes than those in parks and reserves, exhibiting sometimes typical signatures of more than one biome; (3) free-roaming Cape elephants from fynbos areas have significant amounts of Restionaceae phytoliths, which suggests that grazing on restios in grass-poor fynbos types was important; (4) short saddles, typical of Chloridoideae grasses, are always the most abundant short-cell morphotypes in dental samples, even in areas where other grass subfamilies dominate, and (5) with some limitations, the study of phytoliths in herbivore dental calculus has a high, largely unexplored, potential in paleoecology and conservation ecology.

光学・電子顕微鏡によるクワの葉プラントオパールおよびその不均一分布の観察

光学・電子顕微鏡によるクワの葉プラントオパールおよびその不均一分布の観察

Light and SEM observation of opal phytoliths in the mulberry leaf

Biogenic mineral deposits 25–100μm in diameter were observed by microscopic examination of the leaf of mulberry (Morus alba) ‘Ichinose’. Using chemical mapping with scanning electron microscope, the deposits were determined to be opal phytoliths, composed largely of biogenic silica. Phytoliths varied in diameter and were distributed heterogeneously within a leaf. Many phytoliths were observed in close proximity to small veins. Phytolith growth in the mulberry leaf proceeds by deposition of silicon compounds transferred via the network of cell walls.