Translocation and preservation of soil phytoliths in temperate regions and its implications for palaeoenvironment reconstruction

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The reliability of soil phytoliths within representatives of past phytolith assemblages in archaeological and palaeoecological contexts needs to be improved. In this study, we investigated soil phytolith representation by comparing phytoliths from plant communities with those from paired topsoils and those subjected to vertical translocation at 54 sites in Northeast China. With respect to soil phytolith preservation in the soil-plant system, there is a reasonable correspondence between phytolith morphotypes from forested topsoil (or grassland topsoil) and those from the associated communities. But the comparison and contrast between phytoliths from topsoil and communities indicates that different phytolith morphotypes also exhibit different degrees of representational bias (R values). Additionally, for the vertical translocation of soil phytoliths, together with a phytolith translocation index (T), ~31% and 19% of the phytoliths are transported below the surface of the studied soil profiles in the forested and grassland regions, respectively. The translocation rates of different phytolith morphotypes in the forested samples are all larger than those in the grassland samples. Based on R and T values, the changes of revised topsoil phytolith indices are moderately in accord with actual plant richness and climatic changes. These results we show that the R and T values are effective parameters indicating the degree of soil phytolith preservation and can be used in future studies for developing training sets of modern phytolith assemblages. The results of our study provide a methodological template to investigate the extent to which phytolith assemblages in palaeoenvironmental contexts satisfy the criteria necessary to justify their use as a meaningful proxy of past ecological and climatic change.