A Review on Diagnostic Phytoliths for the Application in Paleovegetation Reconstruction and Environmental Archaeology in East Asia

Phytoliths are extensively utilized as an archaeobotanical indicator in paleovegetation reconstruction and environmental archaeology. Over the past two decades, numerous phytolith morphotypes, particularly those exhibiting diagnostic morphological features and over representative of source plants at the genus and species levels, were discovered and reported. These advancements have significantly contributed to phytolith-based vegetation reconstruction on different timescales, enhanced our understanding of prehistoric plant utilization, and elucidated cultivation and domestication processes of key crops in ancient agriculture. However, there are still inconsistencies and misunderstandings regarding the morphological characteristics of diagnostic phytoliths in various plant groups. This review highlighted the standardization in the classification and description of phytolith morphotypes, and summarized the advancements in phytolith morphology research over the past two decades. Morphological illustrations of diagnostic phytoliths from various plant groups, particularly key crops and their relatives from dryland and rice agriculture in East Asia, were presented as references for phytolith identification and application. Finally, this review proposes future directions for phytolith morphological studies, emphasizing the comprehensive consideration of anatomical structure and morphometric parameters, as well as the need for extensive research on modern plant phytoliths and control experiments on phytolith growth.

Regional features of pollen R-values in China

Establishing a quantitative relationship between modern pollen and vegetation remains a pivotal but intricate pursuit within the field of Quaternary palynology.The R-value,a well-established and traditional metric characterized by its simplicity and direct applicability,serves to calibrate the nonlinear disparities between surface pollen and modern vegetation.This study entails the construction of a comprehensive pollen R-value dataset for China derived from R-values published between 1987 and 2021.The dataset,compiled after rigorous screening,calibration,and standardization processes,encompasses 898 modern pollen sampling sites and 2115 pollen R-value data entries,encapsulating 152 pollen taxa spanning 65 families and 113 genera.Synthesizing the extracted R-values yielded the following insights:(1)A macrospatial analysis validates previously established knowledge at a site-specific scale.Evidently,pollen R-value variations across China are statistically significant.Approximately two-thirds of pollen taxa exhibit underrepresentation(e.g.,Taxodiaceae,Corylus,Nitraria,Tamarix,Cyperaceae,Poaceae,and Fabaceae),while the remaining one-third display overrepresentation(e.g.,Pinus,Picea,Betula,Ephedra,Chenopodiaceae,and Artemisia).The degree of underrepresentation surpasses that of overrepresentation,and the representation patterns of Castanea,Quercus,Polygonaceae,and Asteraceae are contingent upon vegetation types.(2)Pollen R-values follow distinct spatial distribution patterns within China.In the woody vegetation region of eastern China,R-values progressively decline from north to south,correlating with rising temperatures and precipitation.Conversely,in herbaceous vegetation regions of northern and western China,R-values decrease from east to west and from northeast to southwest,corresponding to increased aridity.Nevertheless,pollen R-values manifest variation contingent on pollen taxa,vegetation types,and climatic regions,even differing for the same taxa across varying vegetation types and climatic conditions.This highlights the intricate nature of pollen R-values and their interpretation of pollen-vegetation relationships.(3)Pollen R-values and relative pollen production estimates exhibit resemblances and a modest positive correlation.However,adjudicating between them as representatives of vegetation requires nuanced consideration,as both metrics convey pollen representation within vegetation,demonstrating the multifaceted relationships they share with modern vegetation.Further recommendations suggest that when assessing pollen representation in modern vegetation,fossil pollen content should be weighted using either the median or log-transformed R-value.This approach underscores the necessity of comprehensively accounting for divergences and convergences across various spatial scales and vegetation types,particularly the disparities observed within identical pollen taxa across dissimilar regions.