The impact of different forest types on phytolith-occluded carbon accumulation in subtropical forest soils

Occlusion of carbon in phytoliths is an important biogeochemical carbon sequestration mechanism and plays a significant role in the global biogeochemical carbon cycle and atmospheric carbon dioxide (CO2) concentration regulation at a millennial scale. However, few studies have focused on the storage of phytolith and phytolith-occluded carbon (PhytOC) in subtropical forest soils. Soil profiles with 100-cm depth were sampled from subtropical bamboo forest, fir forest, and chestnut forest in China to investigate the variation of phytoliths and PhytOC storage in the soil profiles based on amass-balance assessment. The storage of phytoliths in the top 100 cm of the bamboo forest soil (198.13 +/- 25.08 t ha(-1)) was much higher than that in the fir forest (146.76 +/- 4.53 t ha(-1)) and chestnut forest (170.87 +/- 9.59 t ha(-1)). Similarly, the storage of PhytOC in the bamboo forest soil (3.91 +/- 0.64 t ha(-1)) was much higher than that in the fir forest soil (1.18 +/- 0.22 t ha(-1)) and chestnut forest soil (2.67 +/- 0.23 t ha(-1)). The PhytOC percentage in the soil organic carbon pool increased with soil depth and was the highest (4.29 %) in the bamboo forest soil. Our study demonstrated that PhytOC in soil was significantly influenced by forest type and the bamboo forest ecosystem contributed more significantly to phytolith carbon sequestration than other forest ecosystems. Different forest types have a significant influence on the soil PhytOC storage. Optimization of bamboo afforestation/reforestation in future forest management plans may significantly enhance the biogeochemical carbon sink in the following centuries.