The Influence Of Available Soil Silicon On The Formation Of Phytoliths In Plant Community In Northeast China

In recent years, people pay more and more attention to the research of the biogeochemical cycling of silicon, and the application of phytoliths to reconstruct paleoenvironment. However, the formation mechanism of phytoliths is still not clear. In this study,86 sampling sites were set along the 4? annual average temperature isotherm in Northeast China. According to statistics,380 plant samples,403 topsoil samples and 235 soil profile samples were collected. In the laboratory, the phytoliths were extracted using wet-ashing, and counted under the microscope. The available silicon in plant and in soil were analyzed using the molybdenum blue colorimetric method. The data were processed and analyzed by variation coefficient analysis, distance flat value analysis, standardization analysis, correlation analysis and redundancy analysis. Available soil silicon contents in different soil types were studied. The relationships between available soil silicon content, available silicon content in plant community and phytolith concentration in plant community were also analyzed. To investigate the effect of available silicon content in soil-plant system on the formation of phytoliths is helpful to understand the formation mechanism of phytoliths.The conclusions are as follows:(1) The average content of available silicon in each type of soil in Northeast China was:dark brown forest soil 181.74 mg/kg, black soil 217.45 mg/kg, chernozem 349.66 mg/kg, kastanozems 327.52 mg/kg, meadow soil 256.18 mg/kg, albic soil 165.45 mg/kg, swamp soil 130.28 mg/kg, alluvial soil 186.59 mg/kg, paddy soil 182.67 mg/kg, aeolian sandy soil 190.15 mg/kg. The spatial variation of available soil silicon content is influenced by climate, local topography, soil environment and vegetation on the ground. Soil type is different, then the dominant influence factors of the spatial variation of the available soil silicon will be different.(2) The average content of available silicon in plant communities in Northeast China was 307.66 mg/kg. The average content of available silicon in plant communities in the eastern region of Northeast China was 312.98 mg/kg, and it was 282.79 mg/kg in the western region of Northeast China. Due to differences in plant species, available silicon contents in plant communities were different in Northeast China.(3) The phytolith concentrations in plant communities in western region of Northeast China were higher than those in eastern region of Northeast China. The result of correlation analysis showed that:phytolith concentration and silicon content in plant community were significantly positively correlated with available soil silicon content, respectively; Available silicon content in plant community is negatively correlated with available soil silicon content; Phytolith concentration in plant community and the ratio of available silicon content in soil and in plant community were significantly positively correlated. It is suggested that available soil silicon content in soil-plant system affected silicon absorption of plant, and then affected the formation of phytoliths. In a certain range, the higher available soil silicon content is beneficial to the silicon absorption of plant and the formation of phytolits.(4) The available soil silicon content has a significant effect on the formation of each phytolith morphotype. For different phytolith morphotype, the results were different. The higher available soil silicon content in soil-plant system will promote the formation of short cell phytolith, long cell phytolith, bulliform cell phytolith and hair cell phytolith, but the formation of papillate can be inhibited. When the ratio of available silicon content is large, the formation of long cell phytolith and bulliform cell phytolith will be inhibited. The formation of silicified stoma may be affected by available soil silicon content and plan transpiration.