Terrestrial biogeochemical silicon (Si) and carbon (C) cycles couple through various processes, such as silicate weathering and the dynamics resulting from different phytolith assemblages. For example, small amounts of organic C (typically ranging from 0.2 to 5.8%) can be occluded during phytolith formation. Phytoliths play an important role in coupled Si and C cycles. In this study, we analyzed variations in C sequestration and the seasonal dynamics of phytoliths formed in different vegetation types in order to clarify the processes and characteristics of phytolith-occluded-carbon (PhytOC) cycles. Firstly, we measured the variation range of phytolith content in the litter and soil of different vegetation types at 11.87-151.90 and 1.81-14.72 g kg-1, respectively, while we measured the corresponding variation range of PhytOC content at 3.58-24.13 and 0.04-0.65 g kg-1, respectively. We also found that seasonal changes in phytolith and PhytOC content were significant (P < 0.01), both exhibiting a significant decreasing trend from litter to soil and from the surface soil to 0-60 cm of soil layers. Secondly, we measured the variation range of PhytOC storage in the litter and soil (0-60 cm) of different vegetation types at 1.26-6.89 and 28.24-75.2 t, respectively. Finally, our study determined the contribution of PhytOC storage in soil (0.42%) compared with conventionally recognized soil C sequestration storage (0.64%). The phytolith C pool is an important component of the forest ecosystem C pool, which plays a critical role in mitigating global warming.
Keywords: Carbon cycling; PhytOC; Phytolith; Silicon cycling.