Carbon storage potential and seasonal dynamics of phytolith from different vegetation types in a subtropical region, China

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.