Morphological variations of lobate phytoliths from grasses in China and the south-eastern United States

Abstract. Phytolith analysis of grasses is a useful tool in palaeoenvironmental and archaeobotanical research. Lobate phytolith is one of the most important morphotypes of grass phytoliths. This study describes morphological variations of diagnostic lobate phytoliths and produces a tentative classification scheme based on 250 modern grass species from China and the south‐eastern U.S.A. Eighty‐five grass species were found to contain lobate phytoliths. They are derived mainly from Panicoideae, but also include the Chloridoideae, Oryzoideae and Arundinoideae subfamilies. Twenty‐five lobate morphological types were observed from different subfamilies, genera or tribes of grasses, based on two important parameters: (1) the length of the lobate shank and (2) the shape of the outer margin of the two lobes. The identification of grass tribe or even genus is possible based on the differences in lobate shape parameters or the composition of assemblages. However, not all of the lobate assemblages have a definite relationship with the genera that produce them, because grasses can only produce a limited range of lobate shapes that often overlap from one genus to another. Several C₃ grasses and Chloridoideae subfamily grasses also produce characteristic lobate phytoliths. The variations of lobate morphologies can be related to environmental factors, especially moisture. Typical hygrophytic grasses tend to yield lobate phytoliths with very short shank, whereas typical xerophytic grasses tend to produce lobate phytoliths with a very long shank. The potential link between phytolith morphology, grass taxonomy and environmental conditions opens the possibility that phytolith morphology may be used as a proxy in palaeoclimatic reconstruction.     

Identifying inflorescence phytoliths from selected species of wheat (Triticum monococcum, T. dicoccon, T. dicoccoides, and T. aestivum) and barley (Hordeum vulgare and H. spontaneum) (Gramineae)

Analysis of microfossil silica phytoliths is becoming an increasingly important research tool for taxonomists, archaeobotanists, and paleoecologists. Expanded use of phytolith analysis by researchers is dependent upon development of phytolith systematics. In this study phytoliths produced by the inflorescence bracts from four species of wheat, Triticum monoccocum, T. dicoccon, T. dicoccoides, and T. aestivum, and two species of barley, Hordeum vulgare, and H. spontaneum, were analyzed using computer-assisted image and statistical analysis with the intent to develop taxonomic tools to distinguish among the taxa. A classification key based on significant differences among the mean morphometries of the inflorescence phytoliths produced by each species was created and tested. Discriminant analysis of the morphometries of several morphotypes of phytoliths was also conducted to determine whether this computer-assisted statistical procedure could be used as another method to classify the taxa and to determine which morphotypes have measurements that can best be used in discriminant functions. Test results indicated that, at the genus level, both the classification key and discriminant analysis of certain morphotypes of phytoliths were relatively reliable tools for distinguishing among phytoliths produced in the inflorescence bracts of the taxa considered. For distinguishing among the taxa at the species level, the classification key was most reliable. Of the discriminant analyses tested, that based on all the phytolith morphotypes combined was more reliable than those based on only one morphotype.     

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.     

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。     

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.     

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.     

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.     

A reconstruction of the history of a Holocene sand dune on Great Barrier Island, northern New Zealand, using pollen and phytolith analyses

Aim   To reconstruct the history of a Holocene sand dune using pollen and phytolith analyses, and to identify the strengths, weaknesses and compatibility of these two methods in the interpretation of Quaternary coastal environments.
Location  Great Barrier Island, northern New Zealand.
Methods  Pollen and phytolith analyses were carried out on a sequence through a Holocene sand dune containing a palaeosol.
Results  Phytoliths were present throughout the sequence. Grass phytoliths increased at the expense of tree phytoliths following fire disturbance. Pollen (and spores) was preserved only in the palaeosol part of the profile. Pteridium fern spores increased at the expense of tall tree pollen following the fire disturbance.
Main conclusions  Lack of phytolith production by many species and problems of taxonomic specificity in many others restricts the usefulness of phytolith analysis to defining only broad vegetation types. In New Zealand, gymnosperms are invisible in the phytolith record and ferns are extremely under-represented. In contrast, pollen analysis usually provides a great deal of information regarding the composition of a particular vegetation type. The loss of microscopic charcoal fragments during the phytolith extraction process is a disadvantage in the reconstruction of environments where fires have occurred. The greater durability of phytoliths compared with pollen means that phytoliths may be found in sediments where pollen has not been preserved. The phytolith record may also provide evidence of wetter environments that are not apparent in the pollen record. Unlike grass pollen, which is widely dispersed and therefore blurs the spatial record, the presence of grass phytoliths in sediments indicates a local source. The simultaneous application of both methods potentially provides a powerful tool in ecological interpretation and the reconstruction of Quaternary coastal environments.     

First report of phytoliths in the air of Argentina

A first analysis of airborne phytoliths was carried out in Mar del Plata, Argentina. Its primary aims were to characterize the phytolith morphotypes present in the atmosphere, to quantify their abundance and to detect whether seasonal variations exist throughout the year. The standard method was used for monitoring airborne particulate matter applying a Hirst-type suction bioaerosol sampler. The mean daily phytoliths concentrations (p/m3) were calculated for eight selected days from the driest year, 1993, bearing in mind that its atmospheric conditions could favour the presence of biomineralizations in the air. The amount of phytoliths reached was of 1,543. It was composed of 61% isolated and 1% articulated types. The rest were unknown or unidentified phytoliths (38%). The most abundant morphotypes (72.1% of those identified) were elongates, followed by rondels (16.1%) already described for Poaceae subfamilies, such as Pooideae and Stipoideae. Finally, trapeziform and point shaped were identified with 3.8 and 3.4%, respectively. A lower abundance of silica particles was detected on high wind speed days from the south (sea coast) and under wetter conditions. Maximum phytoliths concentrations were recorded in winter when pasture burning is carried out alongside ploughing; this also coincides with the period in which soils were not covered by vegetation. These results shed light on the importance of considering the potential ways of phytoliths dispersion and the factors that could be affecting their aerial transport, especially when they are applied to the interpretation of paleovegetation from phytolith fossil records.     

Understanding Fossil Phytolith Preservation: The Role of Partial Dissolution in Paleoecology and Archaeology

Opaline phytoliths are important microfossils used for paleoecological and archaeological reconstructions that are primarily based on relative ratios of specific morphotypes. Recent studies have shown that phytolith assemblages are prone to post-depositional alteration involving partial dissolution, however, the manner in which partial dissolution affects morphotype composition is poorly understood. Here we show that morphotype assemblages from four different plant species subjected to controlled partial dissolution are significantly different from the original assemblages, indicating that the stability of various morphotypes differs, mainly depending on their surface area to bulk ratios. This underlying mechanism produces distorted morphotype compositions in partially dissolved phytolith assemblages, bearing vast implications for morphotype-based paleoecological and archaeological interpretation. Together with analyses of phytolith assemblages from a variety of archaeological sites, our results establish criteria by which well-preserved phytolith assemblages can be selected for accurate paleoecological and archaeological reconstructions.     

东北地区芦苇植硅体的变化特征

深入研究芦苇(Phragmites australis)不同生长期植硅体的形态变化规律, 对提高古植被重建精度、探讨植硅体形成机理具有重要意义。该文对东北地区12个样点的芦苇叶片进行研究, 选取长势相近、叶片大小一致的芦苇叶片, 用湿式灰化法提取植硅体并对其进行分类和命名。研究发现, 芦苇植硅体主要有5种类型, 在不同生长期内和不同温湿度组合下, 其植硅体类型组合基本无变化, 说明同种植物的植硅体类型组合具有稳定性, 据此可以有效地恢复古植被; 同时芦苇鞍型植硅体百分含量的峰值出现在7月份, 随后稍有减少, 而芦苇扇型植硅体百分含量和浓度的峰值出现在8或9月份, 谷值在7月份。由此推测芦苇鞍型植硅体的形成可能更多地受控于植物的光合作用和蒸腾作用, 芦苇扇型植硅体的形成可能与机动细胞的支撑作用关系密切。实验结果还表明芦苇植硅体浓度并不是随着时间逐渐积累的, 其在8月份达到峰值, 9月份达到谷值, 因此推测植物植硅体浓度的变化规律可能与植物在不同生长期其自身对硅的需求规律相一致。鞍型植硅体浓度的峰值也出现在8月份, 谷值也在9月份, 其浓度变化与芦苇植硅体总浓度的变化趋势相似。     

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％)。     

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.     

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.     

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.     

Phytoliths in woody plants from the northern slope of the Changbai Mountain (Northeast China), and their implication

Phytoliths were extracted from 14 woody plants collected on the northern slope of the Changbai Mountain, including 10 broad-leaved species and 4 conifers. A total of 14 morphotypes of phytoliths were identified, including 3 types first examined in this study. Phytoliths in broad-leaved species were mostly silicified epidermal cells, cell walls, and vascular tissues; phytoliths in conifers were mainly silicified epidermal cells, cell walls, hypodermal cells, and parenchyma cells. Phytoliths produced by broad-leaved species in this region were usually not well silicified, and were fragile, whereas those produced by conifers were better silicified; this might be because of the different lengths of the growth periods. Phytoliths were found have potential in studies of fluctuations of the tree line in this region, and this study also provided a reference for further study of phytoliths in this region and the regional contrast of phytolith assemblages.     

A morphometric study of variance in articulated dendritic phytolith wave lobes within selected species of Triticeae and Aveneae

Morphometric analysis has proven to be an effective tool for distinguishing among phytolith assemblages produced by closely related plant taxa. Elongate dendritic epidermal phytoliths are produced in the inflorescence bracts of many cereal species. Under light microscopy, these articulated dendritic phytoliths produce wave patterns between the margins of the cells that are reported to have taxonomic significance. In this study we explore morphometric variance among the lobes of the wave patterns formed by the articulated dendritic phytoliths within selected species of cereals as a first step towards understanding the variance between species. We found that there is often significant variance in dendritic wave lobes among different accessions of a species, among the different types of inflorescence bracts of the species (glumes, lemmas and paleae), and among each bract type’s location on the inflorescence (upper, middle and lower third of inflorescence spike or panicle). We observed that shape morphometries are typically more reliable and require a smaller sample size for statistical confidence than size morphometries. We further observed that adequate samples sizes for analysis of several shape morphometries of articulated dendritic wave lobes are considerably smaller than those reported to be required for analysis of the same morphometries of individual or isolated dendritic phytoliths. To gain a preliminary sense whether there is potential for discriminating between taxa in light of the significant variance within species, we compared our data to archaeological material from the historical center of Brussels. We demonstrate that while there is considerable variance in the morphometries among accessions, bract types and inflorescence locations within each species, there may yet be potential for discriminating between cereal species in archaeological samples by the morphometries of their dendritic phytolith wave lobes. We present one possible paradigm for conducting such analysis on archaeological material.     

Vegetation and fire history of a Chinese site in southern tropical Xishuangbanna derived from phytolith and charcoal records from Holocene sediments

Aim The aims of this paper are to reconstruct the vegetation and fire history over the past 2000 years in a well‐preserved rain‐forest area, to understand interactions between climate, fire, and vegetation, and to predict how rain forest responds to global warming and increased intensity of human activity. Location Xishuangbanna, south‐west China, 21–22° N, 101–102° E. Methods Phytolith (plant opal silica bodies) morphotypes, assemblages, and indices were used to reconstruct palaeovegetation and palaeoclimate changes in detail. Micro‐charcoal particles found in phytolith slides, together with burnt phytoliths and highly weathered bulliform cells, were employed to reconstruct a record of past fire occurrence. A survey of field sediments, lithology, and ¹⁴C dating were also employed. Results Phytoliths were divided into 11 groups and classified into 33 well‐described morphotypes according to their shape under light microscopy and their presumed anatomical origins and ecological significance. The phytolith assemblages were divided into six significant zones that reveal a complete history of vegetation changes corresponding to climate variation and fire occurrence. Phytolith assemblages and indices show that the palaeoclimate in the study area is characterized by the alternation of warm–wet and cool–dry conditions. Phytolith and charcoal records reveal that 12 fire episodes occurred. Comparison of burnt phytoliths with an aridity index (Iph) shows that fire episodes have a strong relationship with drought events. Main conclusions Our results indicate that fire occurrence in the tropical rain forest of Xishuangbanna is predominantly under the control of natural climate variability (drought events). Nearly every fire episode is coupled with a climatic event and has triggered vegetation composition changes marked by a pronounced expansion of grasses. This indicates that drought interacts with fire to exert a strong influence on the ecological dynamics of the rain forest. However, the impact of human activity in recent centuries is also significant. Our results are important for understanding the interactions between climate, fire, and vegetation, and for predicting how rain forest responds to global warming and increased human activity.