Effects of forest age and bedrock on soil phytolith-occluded organic carbon accumulation of large-diameter bamboo forests in southwest China

To understand the sequestration characteristics and mechanisms of soil PhytOC (phytolith-occluded organic carbon) in large-diameter bamboo forests, the soil PhytOC accumulation of the P. edulis forests and B. emeiensis forests in the karst and non-karst zones of southwest China were studied by the methods of field sampling, laboratory measurement, and statistic analysis. The study yielded the following results and conclusions: 1) The PhytOC content and storage in the 0–30 cm soil profile of the P. edulis forests range from 0.16–1.85 g kg−1 and 0.14–1.41 t hm−2, respectively. Similarly, the PhytOC content and storage in the 0–30 cm soil profile of the B. emeiensis forests vary between 0.56–2.44 g kg−1 and 0.49–2.07 t hm−2, respectively. 2) Stand age and bedrock type significantly influence the accumulation of soil PhytOC in both P. edulis forests and B. emeiensis forests. The mature forests exhibit the highest soil PhytOC content and storage in both types of bamboo forests. Additionally, the soil PhytOC content in karst bamboo forests is notably higher compared to that in the non-karst area. 3) Soil available Si is identified as one of the critical factors affecting the soil PhytOC accumulation in bamboo forests. Results of the present study are of great significance for estimating the phytolith carbon sequestration capacity of bamboo forests and for bamboo forest construction and management aimed at enhancing carbon sequestration.