Phytoliths Analysis for the Discrimination of Foxtail Millet (Setaria italica) and Common Millet (Panicum miliaceum)

Foxtail millet (Setaria italica) and Common millet (Panicum miliaceum) are the oldest domesticated dry farming crops in Eurasia. Identifying these two millets in the archaeobotanical remains are still problematic, especially because the millet grains preserve only when charred. Phytoliths analysis provides a viable method for identifying this important crop. However, to date, the identification of millet phytoliths has been questionable, because very little study has been done on their morphometry and taxonomy. Particularly, no clear diagnostic feature has been used to distinguish between Foxtail millet and Common millet. Here we examined the anatomy and silicon structure patterns in the glumes, lemmas, and paleas from the inflorescence bracts in 27 modern plants of Foxtail millet, Common millet, and closely related grasses, using light microscopy with phase-contrast and microscopic interferometer. Our research shows that five key diagnostic characteristics in phytolith morphology can be used to distinguish Foxtail millet from Common millet based on the presence of cross-shaped type, regularly arranged papillae, Ω-undulated type, endings structures of epidermal long cell, and surface ridgy line sculpture in the former species. We have established identification criteria that, when used together, give the only reliable way of distinguishing between Foxtail millet and Common millet species based on their phytoliths characteristics, thus making a methodological contribution to phytolith research. Our findings also have important implications in the fields of plant taxonomy, agricultural archaeology, and the culture history of ancient civilizations

Glacial-interglacial evolution of seasonal cooling events documented by land-snail eggs from Chinese loess

The alternations of glacial and interglacial cycles are a classical feature of Quaternary climatic evolution and have been demonstrated to be closely related to seasonal insolation changes at high northern latitudes. Therefore, seasonal features may provide insights into glacial-interglacial cycles. However, mainly due to the lack of long time series of seasonally sensitive proxies, little is known about seasonal changes on the glacial-interglacial scale. The unhatched eggs preserved in sediments can serve as a proxy of seasonal cooling events (e.g., cold spells) since biological principles indicate that egg hatching is sensitive to temperature changes, and cooling-event-induced low temperatures during the reproductive season are unfavorable for eggs to hatch. Vertebrate eggs are well documented in the geological records, but they rarely provide continuous records through time. Here we present a high-resolution time series of land-snail eggs from the Chinese Loess Plateau, spanning the last three glacial-interglacial cycles. The results show that seasonal cooling events, indicated by peaks in egg abundance, are strong during glacial inceptions and climate cooling shifts of the marine isotope stages (MIS) 7e/7d, MIS 5e/5d, MIS 5c/5b and MIS 3/2. They tend not to occur during deglacials. They may result in low temperatures unfavorable for egg hatching during the reproductive season. Although several factors may be involved, seasonal cooling events in the Chinese Loess Plateau seem to be positively and more closely related to high-northernlatitude ice sheet growth. This finding may provide a new perspective for understanding glacialinterglacial evolution

Influence of the ratio of planktonic to benthic diatoms on lacustrine organic matter δ13C from Erlongwan maar lake, northeast China

Carbon isotope ratio (δ13Corg) values of organic matter in lake sediments are commonly used to reconstruct environmental change, but the factors which influence change are varied and complex. Here we report δ13C values for sediments from Erlongwan maar lake in northeast China. In this record, changes in δ13C cannot be explained by simple changes in aquatic productivity. Instead, values were likely influenced by differences in the ratio between planktonic and benthic algae, as indicated by the remains of diatoms. This is because the variation of δ13Corg in algae from different habitats is controlled by the thickness of the diffusive boundary layer, which is dependent on the turbulence of the water. Compared with benthic algae, which grow in relatively still water, pelagic algae are exposed to greater water movement. This is known to dramatically reduce the thickness of the boundary layer and was found to cause even more severe δ13C depletion. In Erlongwan maar lake, low values were linked to the dominance of planktonic diatoms during the period commonly known as the Medieval Warm Period. Values gradually increased with the onset of the Little Ice Age, which we interpret as being driven by an increase in the proportion of benthic taxa, due to effect of the colder climate. The increase in planktonic diatoms at the end of the Little Ice Age, linked to higher temperature and a reduction in ice cover, resulted in a further decline in δ13Corg

Phytolith Analysis for Differentiating between Foxtail Millet (Setaria italica) and Green Foxtail (Setaria viridis)

Foxtail millet (Setaria italica) is one of the oldest domesticated cereal crops in Eurasia, but identifying foxtail millets, especially in charred grains, and differentiating it from its wild ancestor, green foxtail (Setaria viridis), in the archaeobotanical remains, is still problematic. Phytolithic analysis provides a meaningful method for identifying this important crop. In this paper, the silicon structure patterns in the glumes, lemmas, and paleas from inflorescence bracts in 16 modern plants of foxtail millet and green foxtail from China and Europe are examined using light microscopy with phase-contrast and a microscopic interferometer. Our research shows that the silicon structure of ΩIII from upper lemmas and paleas in foxtail millet and green foxtail can be correspondingly divided into two groups. The size of ΩIII type phytolith of foxtail millet is bigger than that from green foxtail. Discriminant function analysis reveals that 78.4% of data on foxtail millet and 76.9% of data on green foxtail are correctly classified. This means certain morphotypes of phytoliths are relatively reliable tools for distinguishing foxtail millet from green foxtail. Our results also revealed that the husk phytolith morphologies of foxtail millets from China and Eastern Europe are markedly different from those from Western Europe. Our research gives a meaningful method of separating foxtail millet and green foxtail. The implications of these findings for understanding the history of foxtail millet domestication and cultivation in ancient civilizations are significant

Phytoliths as a tool for investigations of agricultural origins and dispersals around the world

Agricultural origins and dispersals are subjects of fundamental importance to archaeology as well as many other scholarly disciplines. These investigations are world-wide in scope and require significant amounts of paleobotanical data attesting to the exploitation of wild progenitors of crop plants and subsequent domestication and spread. Accordingly, for the past few decades the development of methods for identifying the remains of wild and domesticated plant species has been a focus of paleo-ethnobotany. Phytolith analysis has increasingly taken its place as an important independent contributor of data in all areas of the globe, and the volume of literature on the subject is now both very substantial and disseminated in a range of international journals. In this paper, experts who have carried out the hands-on work review the utility and importance of phytolith analysis in documenting the domestication and dispersals of crop plants around the world. It will serve as an important resource both to paleo-ethnobotanists and other scholars interested in the development and spread of agriculture

Macro-Process of Past Plant Subsistence from the Upper Paleolithic to Middle Neolithic in China: A Quantitative Analysis of Multi-Archaeobotanical Data.

Detailed studies of the long-term development of plant use strategies indicate that plant subsistence patterns have noticeably changed since the Upper Paleolithic, when humans underwent a transitional process from foraging to agriculture. This transition was best recorded in west Asia; however, information about how plant subsistence changed during this transition remains limited in China. This lack of information is mainly due to a limited availability of sufficiently large, quantified archaeobotanical datasets and a paucity of related synthetic analyses. Here, we present a compilation of extensive archaeobotanical data derived from interdisciplinary approaches, and use quantitative analysis methods to reconstruct past plant use from the Upper Paleolithic to Middle Neolithic in China. Our results show that intentional exploitation for certain targeted plants, particularly grass seeds, may be traced back to about 30,000 years ago during the Upper Paleolithic. Subsequently, the gathering of wild plants dominated the subsistence system; however, this practice gradually diminished in dominance until about 6~5 ka cal BP during the Middle Neolithic. At this point, farming based on the domestication of cereals became the major subsistence practice. Interestingly, differences in plant use strategies were detected between north and south China, with respect to (1) the proportion of certain plant taxa in assemblages, (2) the domestication rate of cereals, and (3) the type of plant subsistence practiced after the establishment of full farming. In conclusion, the transition from foraging to rice and millet agriculture in China was a slow and long-term process spanning 10s of 1000s of years, which may be analogous to the developmental paths of wheat and barley farming in west Asia

Evidence for northeastern Tibetan Plateau uplift between 25 and 20 Ma in the sedimentary archive of the Xining Basin, Northwestern China

International audienceThe growth history of the Tibetan Plateau provides a valuable natural laboratory to understand tectonic processes of the India-Asia collision and their impact on and interactions with Asian and global climate change. However, both Tibetan Plateau growth and Asian paleoenvironments are generally poorly documented in pre-Pliocene times and reflect limited temporal coverage for different parts of the plateau. Here we present magnetostratigraphic results from the Xining Basin, at the NE margin of the Tibetan Plateau, precisely dating the record between the earliest Oligocene (~33 Ma) to the middle Miocene (~16 Ma). The pattern of observed paleomagnetic polarity zones is unequivocally correlated to the geomagnetic polarity time scale (GPTS) indicating relatively constant and low sediment accumulation rates (32 m/Myr) except for a peculiar period of unstable accumulation between 25.3 and 19.7Ma. At the beginning of this interval, a marked permanent increase in magnetite content of the sediments is observed and likely relates to a change in provenance. We directly relate this unstable period of sediment accumulation and provenance change to the coeval exhumation recently reported by low-temperature thermochronology from the Laji Shan range, which subsequently formed the southernmargin of the Xining Basin. Evidence for NE Tibet tectonismat 25-20 Ma can be associated with widespread deformation over the entire Himalayan-Tibetan orogen at this time, which may be linked to the coeval appearance of monsoon climate in Eastern Asia and the onset of central Asian desertification