Topsoil phytolith assemblages are related to precipitation via different vegetation types in Northeast China

The characteristics of topsoil phytolith assemblages can reflect the local vegetation and climatic conditions. We collected 53 topsoil samples along an isotherm corresponding to a mean annual temperature (MAT) of 4 °C in Northeast China, 20 samples were from the Daxing'an Mountains (DXAM), 18 samples from the Songnen Plain (SNP), and 15 samples from the Changbai Mountains (CBM). The phytoliths were classified into 13 morphological categories. We observed significant differences between the phytoliths assemblages from the DXAM, SNP, and CBM, and they could be statistically discriminated with a total accuracy of 81.1%. ELONGATE percentages were more sensitive to MAT than to mean annual precipitation (MAP). There was a significant positive correlation between the percentages of ELONGATE, PTERIDOPHYTE-TYPE, PAPILLATE and MAP; and a significant negative correlation between the percentages of BILOBATE and MAP. We constructed a phytolith index (D/W) based on the common phytolith types, which reflects changes in environmental humidity: D/W = BILOBATE / (BILOBATE + ELONGATE); the higher the value of D/W the drier the environment, and vice versa. In Northeast China, D/W varied from 0.0 to 0.6, with the average of 0.3. D/W < 0.3 corresponded to a relatively humid climate, and D/W > 0.3 corresponded to a relatively dry climate.