Diversity of lobate phytoliths in grass leaves from the Sahel region, West Tropical Africa: Tribe Paniceae

Phytoliths are microscopic amorphous silicon dioxide (SiO2.H2O) particles occurring in leaves, internodes, glumes and inflorescence within all members of the grass family Poaceae. Phytoliths of grasses are of particular interest, as they possess morphological features which have encouraged many investigators to identify these plants from which fossil phytoliths might have originated. The present study is a step towards preparing a systematic inventory of grass phytoliths in western tropical Africa. Morphology and dimensions of phytoliths from 66 species belonging to the tribe Paniceae have been studied. Four shape categories of lobate phytoliths have been determined in leaf blade spodograms: bilobate, nodular bilobate, polylobate, quadra-lobate. Bilobate shaped phytoliths are frequently represented in all genera of Paniceae. 13 groups of lobate phytoliths have been distinguished based on significant morphological criteria like shape of outer margins, shape of the shank and number of lobes. A size category system of lobate phytolith dimensions (length, width; length and width of shanks) has been developed by the analysis of average, minimum and maximum values of these dimensions. Application of the size category system results on classifying the major groups into 25 subgroups. The study proves that size and shape can be used to assign some of the lobate phytoliths to their respective genera. Some rarely produced lobate shapes like nodular bilobate and polylobate types could be used together on assemblage basis as markers for definite genera in the tribe Paniceae, e.g. Brachiaria, Panicum, Pennisetum and Setaria. Also, bilobate phytoliths with concave margins have been recorded in five species. Bilobate phytoliths with flattened and convex margins and quadra-lobate shapes are produced by almost all species which therefore resulted in an inconsistent and indefinite relationship with the taxa that produce them. The study shows a correlation between width dimensions of bilobate shapes and their shanks. Greater width dimensions usually connected to thick shanks while short ones are attached to thin shanks. A spectrum on percentages of species producing each type of lobate phytolith has been designed. It is recommended that such spectrum should be carried out for all tribes of Poaceae on phyto-geographical basis which might eliminate the effect of redundancy and multiplicity on the classification of grass phytoliths.     

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.     

内蒙古典型草原禾本科植硅体形态

运用地层中植硅体组合解释过去草原植被及气候变化的关键之一,是要了解研究区现代植硅体形态及表土植硅体组合与现代植被的关系。文中研究内蒙古典型草原禾本科植物根、茎、叶、芒以及种子等不同部位的植硅体,对其中的12种主要禾本科植物叶表皮短细胞硅酸体进行分类及统计。研究表明：内蒙古典型草原禾本科叶表皮短细胞硅酸体可分为8种特殊形态类型。C3植物早熟禾亚科的叶表皮短细胞硅酸体形态多样。几乎所有早熟禾亚科都能产生圆型硅酸体,以贝加尔针茅(85．5％)、大针茅(89．7％)、克氏针茅(90％)以及芨芨草(96．6％)中的圆型硅酸体含量最丰富。针茅哑铃型主要见于针茅植物叶表皮短细胞中,克氏针茅的针茅哑铃型含量相对较高。羊草中未见针茅哑铃型硅酸体。浴草、披缄草叶表皮短细胞硅酸体以齿型为主,分别含87．3％和57．2％,齿型在硬质早熟禾中也占一定比例。沙生冰草中的脊圆型占优势,含74．4％。C3植物早熟禾亚科的叶表皮短细胞产生的截锥型硅酸体含量较少。C4植物虎尾草亚科中的糙隐子草叶表皮短细胞硅酸体以黍哑铃型、简单哑铃型、鞍型为主;黍亚科狗尾草则以黍哑铃型占优势(82．9％)。     

中国-中新世湖泊的古生态:根据山旺盆地植硅体的初步解释

山东山旺中新世山旺组湖相沉积中富含保存精美的古生物化石。对于湖相沉积中的昆虫、植物和哺乳动物化石,前人已经做了大量的研究工作。其中植物大化石和孢粉的研究结果表明,中新世山旺组在沉积期间,山旺湖周围的植被处于湿润的暖温带到亚热带的古生态环境下。哺乳动物蝙蝠和貘化石的研究结果也支持这个结论。然而,迄今为止,还没有关于草本植物的种类组成及含量的研究报道。本文首次对山旺组样品中的植硅体进行了研究,为山旺中新世植被的研究提供了新的证据。对从6块山旺组样品中分析出的植硅体进行研究的结果表明,山旺中新世植硅体组合含有丰富的保存极好的草本植物植硅体,代表森林成分的双子叶植物植硅体,以及偶尔出现的棕榈科植硅体。草本植物的植硅体主要来自于C_3/C_4禾本科的PACCAD类群和早熟禾亚科的植物,少数可能来自于在林下封闭生活环境中生长的草本植物。山旺中新世植硅体组合显示,在湖边森林生活环境下,伴生大量的适合沼生到中生环境的草本植物,在较干旱的地区生长着早熟禾(和PACCAD)的草本植物。本文的研究结果进一步支持山旺中新世气候比现在更加湿润而且变动较小的观点。山旺中新世植硅体组合与土耳其和北美大平原中新世湖相沉积中的植硅体组合不同,后者的植硅体组合主要是由多种C_3早熟禾亚科草本和不同种类的PACCAD类群草本植物组成。今后的研究工作将进一步揭示这种差异是否反映了草本植物群落在大尺度的生物地理上的差异,或者是由于地区性的局部气候不同所导致。     

Grass water stress estimated from phytoliths in West Africa

Aim This study calibrates the relationship between phytolith indices, modern vegetation structure, and a climate parameter (AET/PET, i.e. the ratio of annual actual evapotranspiration to annual potential evapotranspiration), in order to present new proxies for long‐term Quaternary climate and vegetation changes, and model/data comparisons. Location Sixty‐two modern soil surface samples from West Africa (Mauritania and Senegal), collected along a latitudinal transect across four bioclimatic zones, were analysed. Methods Two phytolith indices are defined as normalized data: (1) humidity‐aridity index [Iph (%) = saddle vs. cross + dumbbell + saddle], and (2) water stress index [fan‐shaped index (Fs) (%) = fan‐shaped vs. sum of characteristic phytoliths]. Vegetation structures are delimited according to Iph and Fs boundaries. Bootstrapped regression methods are used for evaluating the strength of the relationship between the two phytolith indices and AET/PET. Additional modern phytolith assemblages, from Mexico, Cameroon and Tanzania are extracted in order to test the calibration established from the West African samples. Accuracy of the AET/PET phytolith proxy is compared with equivalent pollen proxy from the same area. Results Characterization of the grass cover is accurately made through Iph. A boundary of 20 ± 1.4% discriminates tall grass savannas from short grass savannas. Water stress and transpiration experienced by the grass cover can be estimated through Fs. AET/PET is accurately estimated from phytoliths by a transfer function: AET/PET = ?0.605 Fs ? 0.387 Iph + 0.272 (Iph – 20)² (r = 0.80 ± 0.04) in the application domain (AET/PET ranging from 0.1 ± 0.04 to 0.45 ± 0.04). Phytolith and pollen estimate with similar precision (r_pollen = 0.84 ± 0.04) the AET/PET in the studied area. Conclusions This study demonstrates that we can rely on the phytolith indices Iph and Fs to distinguish the different grasslands in tropical areas. Moreover, a new phytolith proxy of AET/PET, linked to water availability, is presented. We suggest from these results that combining phytolith and pollen proxies of AET/PET would help to constrain this climate parameter better, especially when phytolith assemblages are dominated by Panicoideae and Chloridoideae C₄‐grass phytoliths, are devoid of Pooideae C₃‐grass phytoliths, and occur with a few tropical ligneous woody dicotyledon phytoliths. As AET/PET is a bioclimatic indicator commonly used in vegetation models, such a combination would help to make model/data comparisons more efficient.     

青藏高原常见早熟禾亚科植硅体形态特征初步研究

文章对采自青藏高原地区早熟禾亚科（Pooideae）常见的10属19种现代植物进行详细的植硅体形态描述、分类、统计、测量和对比。分析发现：青藏高原现生植物早熟禾亚科（Pooideae）特有的植硅体形态主要包括帽型、齿型、针茅哑铃型和针茅多铃型,同时发育塔型、棒型、尖型、刺球型等其它亚科常见的类型。初步明确了部分属一级的植硅体形态特点,例如,羊茅属（Festuca）、早熟禾属（Poa）等主要发育尖顶帽型;长芒草（Stipa bungeana Trin．）、赖草（Leymus secalinus（Georgi）Tzvel．）等主要发育平顶帽型;针茅属（Stipa）主要发育针茅哑铃型;早熟禾属（Poa）、三毛草属（Trisetum）同时发育较丰富的帽型和齿型。为进一步地深入研究该区草原植被群落的演替过程和规律提供了植硅体形态学分析的基础。     

The spread of grass-dominated habitats in Turkey and surrounding areas during the Cenozoic: Phytolith evidence

The arrival of hipparionine horses in the eastern Mediterranean region around 11 Ma was traditionally thought to mark the simultaneous westward expansion of savanna vegetation across Eurasia. However, recent paleoecological reconstructions based on tooth wear, carbon isotopes, and functional morphology indicate that grasses played a minor role in Late Miocene ecosystems of the eastern Mediterranean, which were more likely dry woodlands or forests. The scarcity of grass macrofossils and pollen in Miocene floras of Europe and Asia Minor has been used to support this interpretation. Based on the combined evidence, it has therefore been suggested that Late Miocene ungulate faunal change in the eastern Mediterranean signals increased aridity and landscape openness, but not necessarily the development of grass-dominated habitats.

To shed new light on the Miocene evolution of eastern Mediterranean ecosystems, we used phytolith assemblages preserved in direct association with faunas as a proxy for paleovegetation structure (grassland vs. forest). We extracted phytoliths and other biogenic silica from sediment samples from well-known Early to Late Miocene ( 20–7 Ma) faunal localities in Greece, Turkey, and Iran. In addition, a Middle Eocene sample from Turkey yielded phytoliths and served as a baseline comparison for vegetation inference.

Phytolith analysis showed that the Middle Eocene assemblage consists of abundant grass phytoliths (grass silica short cells) interpreted as deriving from bambusoid grasses, as well as diverse forest indicator phytoliths from dicotyledonous angiosperms and palms, pointing to the presence of a woodland or forest with abundant bamboos. In contrast, the Miocene assemblages are dominated by diverse silica short cells typical of pooid open-habitat grasses. Forest indicator phytoliths are also present, but are rare in the Late Miocene (9–7 Ma) assemblages. Our analysis of the Miocene grass community composition is consistent with evidence from stable carbon isotopes from paleosols and ungulate tooth enamel, showing that C₄ grasses were rare in the Mediterranean throughout the Miocene. These data indicate that relatively open habitats had become common in Turkey and surrounding areas by at least the Early Miocene ( 20 Ma), > 7 million years before hipparionine horses reached Europe and arid conditions ensued, as judged by faunal data.     

Phylogenetic niche conservatism in C4 grasses

Photosynthetic pathway is used widely to discriminate plant functional types in studies of global change. However, independent evolutionary lineages of C₄ grasses with different variants of C₄ photosynthesis show different biogeographical relationships with mean annual precipitation, suggesting phylogenetic niche conservatism (PNC). To investigate how phylogeny and photosynthetic type differentiate C₄ grasses, we compiled a dataset of morphological and habitat information of 185 genera belonging to two monophyletic subfamilies, Chloridoideae and Panicoideae, which together account for 90 % of the world’s C₄ grass species. We evaluated evolutionary variance and covariance of morphological and habitat traits. Strong phylogenetic signals were found in both morphological and habitat traits, arising mainly from the divergence of the two subfamilies. Genera in Chloridoideae had significantly smaller culm heights, leaf widths, 1,000-seed weights and stomata; they also appeared more in dry, open or saline habitats than those of Panicoideae. Controlling for phylogenetic structure showed significant covariation among morphological traits, supporting the hypothesis of phylogenetically independent scaling effects. However, associations between morphological and habitat traits showed limited phylogenetic covariance. Subfamily was a better explanation than photosynthetic type for the variance in most morphological traits. Morphology, habitat water availability, shading, and productivity are therefore all involved in the PNC of C₄ grass lineages. This study emphasized the importance of phylogenetic history in the ecology and biogeography of C₄ grasses, suggesting that divergent lineages need to be considered to fully understand the impacts of global change on plant distributions.     

Phytoliths of Indian grasses and their potential use in identification

Phytoliths are amorphous silicon dioxide (SiO₂.nH₂O) inclusions abundant in leaves, in-ternodes and glumes in members of Poaceae. They may occur as inclusions filling the entire lumen of the silica cells, bulliform cells and trichomes or may be part of the outer epidermal cell walls. Since phytoliths are resistant to fungal or animal digestive juices, a large quantity of phytoliths accumulate in the soil where grasses grow. Compared with the pollen grains of grasses which tend to be uniform, phytoliths vary in sue and morphology and can be of value in identification at different taxonomic levels and in the dating of past vegetation. The size and shape of phytoliths of about 100 species of grasses from Tamil Nadu, India, have been determined. Silica bodies were observed either after isolation or in cleared leaf blades. Size and shape of phytoliths were determined under a microscope or from micrographs of the specimens. Size and shape can be used to assign the phytoliths to their respective subfamilies and to distinguish some of the grasses at the generic level. Drawings of silica cells and an identification key are provided for 80 species.     

Prairie grass phytolith hardness and the evolution of ungulate hypsodonty

Silica phytoliths in grasses are thought to serve as a defence mechanism against grazing ungulates by causing excessive tooth wear. It is posited that they contributed to the evolution of hypsodonty in these animals. However, some have questioned whether grass phytoliths can abrade enamel. Here Mohs hardness testing was conducted on Blue Grama grass (Bouteloua gracilis) to determine phytolith hardness. Microindentation was performed on horse and American bison molars to establish dental constituent hardness values. To infer the phytoliths' abrasion capacity, the hardness values were contrasted. Phytolith hardness ranged from 18.0 to 191.5 HV. This is considerably softer than the values obtained for ungulate enamel, which range from 332.6 to 363.4 HV, but harder than the other dental constituents. Although Blue Grama phytoliths are incapable of directly abrading enamel, when viewed in conjunction with other data on phytolith hardness, there is considerable variation across grass species and some phytoliths are actually harder than ungulate enamel. Blue Grama grass phytoliths may even promote enamel wear due to pressure accentuation caused by the recession of softer tissues. Given these findings and considerations, it is plausible phytoliths served an integral role in the co-evolution of grasses and herbivorous ungulates, although more testing is needed to bear this out.     

Phytolith assemblages in grasses native to central Argentina

BACKGROUND AND AIMS: Phytolith reference collections are a prerequisite for accurate interpretation of soil phytolith assemblages aimed at reconstructing past vegetation. In this study a phytolith reference collection has been developed for several grasses native to central Argentina: Poa ligularis, Piptochaetium napostaense, Stipa clarazii, Stipa tenuis, Stipa tenuissima, Stipa eriostachya, Stipa ambigua, Stipa brachychaeta, Pappophorum subbulbosum, Digitaria californica, Bothriochloa edwardsiana and Aristida subulata. METHODS: For each species, phytoliths present in the leaf blades were classified into 47 morphotypes, and their relative frequency determined by observing 300-400 phytoliths per sample (n = 5). Data were analyzed by complete linkage cluster analysis, using the Morisita Index as measure of association. KEY RESULTS: The results showed differentiation among phytolith assemblages at species level or at plant functional type level. Cluster analysis separated C3 from C4 species and palatable from non-palatable species. CONCLUSIONS: This study highlights the possibility of reconstructing past vegetation in central Argentina grasslands through the analysis of soil phytolith assemblages.     

Epidermal Patterning and Silica Phytoliths in Grasses: An Evolutionary History

Due to the immense ecological and economic significance of grasses, their highly characteristic long–short epidermal patterning and associated silica phytoliths represent significant diagnostic markers in studies of ancient climate change and agriculture. We explore the link between epidermal cell patterning and phytolith development and review the evolutionary history of phytoliths in the context of recent well-resolved phylogenetic analyses of grasses and allied Poales, focusing on early-divergent grasses and the subfamilies that constitute the BEP group (the bamboos and their allies). Dimorphic epidermal patterning is a common feature of Poaceae and the related family Joinvilleaceae, where phytoliths are located primarily in the short cells. However, Joinvillea lacks the short-cell pairs that occur in many grasses. The costal rows of phytoliths that characterize some grasses could represent loss of long–short cell patterning over the veins. Unlobed phytoliths probably represent the ancestral condition in grasses, though bilobate phytoliths evolved at an early stage. Either transverse-unlobed or transverse-bilobate phytoliths predominate in the early-divergent lineages, whereas axial-bilobates (or polylobates) primarily characterize the PACMAD clade and the BEP subfamily Pooideae.     

Teosinte inflorescence phytolith assemblages mirror Zea taxonomy

Molecular DNA analyses of the New World grass (Poaceae) genus Zea, comprising five species, has resolved taxonomic issues including the most likely teosinte progenitor (Zea mays ssp. parviglumis) of maize (Zea mays ssp. mays). However, archaeologically, little is known about the use of teosinte by humans both prior to and after the domestication of maize. One potential line of evidence to explore these relationships is opaline phytoliths produced in teosinte fruit cases. Here we use multidimensional scaling and multiple discriminant analyses to determine if rondel phytolith assemblages from teosinte fruitcases reflect teosinte taxonomy. Our results indicate that rondel phytolith assemblages from the various taxa, including subspecies, can be statistically discriminated. This indicates that it will be possible to investigate the archaeological histories of teosinte use pending the recovery of appropriate samples.     

Photosynthetic pathway variation among C4 grasses along a precipitation gradient in Argentina

Aim Based on the biochemical and physiological attributes of C₄ grasses, and on the close association between decarboxylation pathways and the taxa in which they evolved, the hypotheses tested were: (1) that C₄ grasses would become progressively more abundant as precipitation decreased, with grasses of the NADP‐me subtype more abundant in wetter sites and those of the NAD‐me subtype more common in arid regions; and (2) that the distribution of grass subfamilies would also be correlated with annual precipitation. Location The study was conducted along a precipitation gradient in central Argentina, from the eastern Pampas (>1000 mm year^?1) to the western deserts and semi‐deserts near the Andes (<100 mm year^?1). Methods Percentage of species and relative cover of C₃ and C₄ grasses (including C₄ subtypes) in local floras from 15 lowland sites of central Argentina were obtained from our own unpublished data and from recently published floristic surveys. Pearson correlation coefficients were obtained between grass distribution parameters and the available climatic data. Results The percentage of C₄ grasses increased towards the arid extreme and showed a strong negative correlation with annual rainfall (r = ?0.74, P < 0.01). Within the C₄ subtypes, the NADP‐me species showed a higher proportional representation at the wetter extreme, whereas the representation of NAD‐me species increased towards the more arid extreme. The relationship of PEP‐ck species with climatic parameters in central Argentina was less evident. The distributions of the Panicoideae and Chloridoideae subfamilies along the precipitation gradient were diametrically opposed, with the Panicoideae positively (r = 0.86, P < 0.001) and the Chloridoideae negatively (r = ?0.87, P < 0.001) correlated with annual precipitation. Main conclusions Our data are consistent with the broad observation that C₄ grasses tend to dominate in areas where the wet season falls in the warmer summer months. In agreement with previously reported results for Africa, Asia, Australia and North America, we describe here for the first time a significant relationship between annual precipitation and the prevalence of the NADP‐me and NAD‐me photosynthetic pathways along climatic gradients for the Neotropics. We also report for the first time that correlations between C₄ species and annual rainfall are stronger when the relative cover of grass species is considered. The association of grass subfamilies Panicoideae and Chloridoideae with rainfall is as strong as that recorded for the NADP‐me and NAD‐me variants, respectively, suggesting that characteristics other than decarboxylation type may be responsible for the geographic patterns described in this study.     

Biogeography of the grasses (Poaceae): a phylogenetic approach to reveal evolutionary history in geographical space and geological time

The grasses (Poaceae) are the fifth most diverse family of angiosperms, including 800 genera and more than 10 000 species. Few phylogenetic studies have tried to investigate palaeo‐biogeographical and palaeo‐ecological scenarios that may have led to present‐day distribution and diversity of grasses at the family level. We produced a dated phylogenetic tree based on combined plastid DNA sequences and a comprehensive sample of Poaceae. Furthermore, we produced an additional tree using a supermatrix of morphological and molecular data that included all 800 grass genera so that ancestral biogeography and ecological habitats could be inferred. We used a likelihood‐based method, which allows the estimation of ancestral polymorphism in both biogeographical and ecological analyses for large data sets. The origin of Poaceae was retrieved as African and shade adapted. The crown node of the BEP + PACCMAD clade was dated at 57 Mya, in the early Eocene. Grasses dispersed to all continents by approximately 60 million years after their Gondwanan origin in the late Cretaceous. PACCMAD taxa adapted to open habitats as early as the late Eocene, a date consistent with recent phytolith fossil data for North America. C₄ photosynthesis first originated in Africa, at least for Chloridoideae in the Eocene at c. 30 Mya. The BEP clade members adapted to open habitats later than PACCMAD members; this was inferred to occur in Eurasia in the Oligocene. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 543–557.     

Advantages and disadvantages of phytolith analysis for the reconstruction of Mediterranean vegetation: an assessment based on modern phytolith, pollen and botanical data (Luberon, France)

We present here the results of a first study comparing modern soil phytolith assemblages with pollen and botanical data at a North Mediterranean site. This work has shown the following limitations and advantages of phytolith analysis for the reconstruction of Mediterranean vegetation:(1) Phytoliths are produced in sufficient quantities for analysis and are well preserved in limestone environments, widespread in the Mediterranean area. (2) Young stands of Quercus ilex and Quercus coccifera, widely distributed in the Mediterranean area do not produce characteristic phytolith types in sufficient quantities to allow the calculation of a reliable index of tree cover density. (3) Pine forests, dominated by Pinus halepensis and Pinus sylvestris, are not recorded in the studied phytolith assemblages. (4) Grassland and shrubland assemblages can be distinguished through their associated phytolith assemblages, in particular by the proportion of crenate phytoliths produced in the short cells of the grass epidermis. (5) The different vegetation groups on the massif cannot be distinguished by pollen analysis. Further studies, comparing modern phytolith assemblages and quantitative vegetation data, should be carried out on forest plots that have been established for several centuries to further assess the role of phytolith analysis in vegetation reconstructions in the Mediterranean region.     

Inter- and intraspecific variation in grass phytolith shape and size: a geometric morphometrics perspective

Background and AimsThe relative contributions of inter- and intraspecific variation to phytolith shape and size have only been investigated in a limited number of studies. However, a detailed understanding of phytolith variation patterns among populations or even within a single plant specimen is of key importance for the correct taxonomic identification of grass taxa in fossil samples and for the reconstruction of vegetation and environmental conditions in the past. In this study, we used geometric morphometric analysis for the quantification of different sources of phytolith shape and size variation.MethodsWe used landmark-based geometric morphometric methods for the analysis of phytolith shapes in two extant grass species (Brachypodium pinnatum and B. sylvaticum). For each species, 1200 phytoliths were analysed from 12 leaves originating from six plants growing in three populations. Phytolith shape and size data were subjected to multivariate Procrustes analysis of variance (ANOVA), multivariate regression, principal component analysis and linear discriminant analysis.Key ResultsInterspecific variation largely outweighed intraspecific variation with respect to phytolith shape. Individual phytolith shapes were classified with 83 % accuracy into their respective species. Conversely, variation in phytolith shapes within species but among populations, possibly related to environmental heterogeneity, was comparatively low.ConclusionsOur results imply that phytolith shape relatively closely corresponds to the taxonomic identity of closely related grass species. Moreover, our methodological approach, applied here in phytolith analysis for the first time, enabled the quantification and separation of variation that is not related to species discrimination. Our findings strengthen the role of grass phytoliths in the reconstruction of past vegetation dynamics.     

Bronze Age crop processing evidence in the phytolith assemblages from the ditch and fen around Fondo Paviani,northern Italy

The Terramare civilization (ca. 1650–1150 cal bce) on the Po plain in northern Italy is considered to have been an agrarian society typical of the European Bronze Age, with a subsistence economy based on arable and livestock farming, and which showed some innovations such as the introduction of millets as cultivars. Some questions are still open concerning the agricultural system, the food and non-food uses of plant resources and the organization of labour at these sites. In this paper, for the first time, phytolith analysis has been integrated with more standard archaeobotanical methods applied to material from the long-lasting settlement of Fondo Paviani, Verona. The aim of the study was to use phytoliths as a tool to investigate the cereal economy in order to detect different grass subfamilies and possibly provide hints about local crop processing activities. For this purpose, two contexts, a shallow ditch at the edge of the site that had been filled with domestic waste and a near-site fen with natural infilling, have been the objects of a multi-proxy inter-disciplinary investigation. This includes the analyses of phytoliths, pollen, NPP, sediment texture and micromorphology. The phytolith record shows remains of panicoid as well as pooid grasses, including chaff material with frequent traces of threshing that indicate the processing of cereals at the site and the possible use of chopped straw as fodder. The comparison of different kinds of evidence strengthens the interpretation and offers a new perspective on the application of phytolith analysis to Bronze Age northern Italy.     

Do soil phytoliths accurately represent plant communities in a temperate region? A case study of Northeast China

Modern soil phytoliths can potentially provide analogues for phytolith assemblages from archaeological and palaeoecological contexts. To assess the reliability of soil phytoliths for representing different plant communities, we analysed phytoliths in surface soils and parent plants at 65 sites representing five types of regional vegetation in Northeast China. The results demonstrated that surface soil phytolith assemblages could clearly differentiate samples from herbaceous and woody communities, and samples from Poaceae and non-Poaceae communities could be separated statistically. In addition, woody communities could be differentiated into a broadleaf-Poaceae community, a broadleaf-non-Poaceae community and a conifer and broadleaf-non-Poaceae community, except for some overlapping samples. Soil phytolith assemblages are thus able to differentiate regional vegetation types into different plant community types. In the present study, soil phytoliths represented about 30% of the phytoliths present in the aboveground vegetation. In addition, soil phytoliths from different communities reflected the aboveground vegetation with slightly different degrees of accuracy, and in addition different morphotypes exhibited different degrees of representational bias. Some morphotypes (e.g. rondel, elongate psilate, lanceolate) overrepresented the abundance of the associated plant taxa; morphotypes such as tracheid, conical epidermal, stomata and others under-represented the original plant richness; and other morphotypes, e.g. saddle, trapeziform sinuate, scutiform, were in good agreement with the numbers of plant taxa in the plot inventory. Thus, any quantitative palaeovegetation reconstruction using phytoliths should begin with the calibration of soil phytolith assemblages. We conclude that our findings provide improved phytolith analogues for different plant communities, with applications in palaeoenvironmental reconstruction, and they also provide additional insights into the mechanisms of phytolith production and deposition.