Forest age and bedrock significantly change the capacity of soil phytolith carbon sequestration in bamboo forests

Enhancing the total amount and stability of soil organic carbon in ecosystems is of paramount importance for mitigating global climate change. Due to the protection provided by the silica shell, PhytOC (phytolith-occluded organic carbon) is extremely stable compared to other types of organic carbon. On a long-term scale, soil PhytOC accumulation is recognized as one of the significant mechanisms for carbon sequestration and enhancing terrestrial carbon sinks in terrestrial ecosystems. Bamboo forests exhibit extremely significant capabilities for phytolith carbon sequestration. The elucidation of forest age and bedrock effects on the soil PhytOC accumulation will be essential to estimate the phytolith carbon sequestration capacity of bamboo forests and for bamboo forest construction and management aimed at enhancing carbon sequestration. This study demonstrates that forest age and bedrock significantly change the capacity of soil phytolith carbon sequestration in bamboo forests. And soil available Si is the key influencing factor on the soil PhytOC accumulation. The researchers’ finding is appeared at December, 2024 in Soil Ecology Letters.

Professor Sheng said, “The flux of phytolith carbon sink in bamboo forests is 3-80 times greater than that of other forests. The phytoliths in bamboo forests can store 2.05 ± 0.17 Tg of CO₂ annually around the world. Soil PhytOC comes from aboveground plants. The exceptional PhytOC sequestration ability of bamboo plants results in a substantial accumulation of PhytOC in the soil of bamboo forests. Phytolith and PhytOC are generated within the plant body. Following plant senescence, they enter the soil through litter and root decomposition, and are stored in the soil for an extended period. It is evident that the accumulation of soil PhytOC is significantly correlated with the PhytOC sequestration capacity of aboveground vegetation. The physiological metabolism of vegetation varies significantly among different forest ages, which significantly affects its PhytOC sequestration. Consequently, it can be hypothesized that forest age has a significant impact on the accumulation of PhytOC in soil, with a notable increase in soil PhytOC accumulation as forest age increases in bamboo forests.”

“The Si element in phytolith and PhytOC comes from the soil. Soil with high Si content significantly enhances the generation of PhytOC in aboveground vegetation, thereby improving the accumulation of PhytOC in soil. Calcium ions and alkaline environments can weaken the dissolution of PhytOC in soil and alkaline and Ca²⁺-rich soils are beneficial for the preservation of PhytOC. Karst soils exhibit significant characteristics of Ca²⁺-rich, high Si content, and weak alkalinity due to the karstification of their bedrocks. Therefore, the second hypothesis is proposed that karst bedrock has a significant promoting effect on the soil accumulation of PhytOC in bamboo forests, and the soil PhytOC accumulation in karst bamboo forests is significantly higher than that in non-karst bamboo forests.”

“To verify the above two hypotheses, two typical large-diameter bamboo forests (P. edulis forest and B. emeiensis forest) in the bedrocks of karst and non-karst (shale) of southwest China were studied. The accumulation characteristics, laws, and environmental impact factors of soil PhytOC in these bamboo forests were analyzed.” 

In this study, the accumulation characteristics, laws, and environmental impact factors of soil PhytOC accumulation in these bamboo forests were elucidated successfully. Results showed that the stand age significantly influenced the accumulation of soil PhytOC in both P. edulis forests and B. emeiensis forests. Among the three forest ages, regardless of whether they are P. edulis forests or B. emeiensis forests, both the soil PhytOC content and storage are highest in mature forests. The type of bedrock also significantly impacts the accumulation of soil PhytOC in both P. edulis forests and B. emeiensis forests. The soil PhytOC content of the two types of bamboo forests in the karst area is notably higher compared to that in the non-karst area. The content of soil available Si is significantly positively correlated with soil phytolith content, PhytOC content, the ratio of PhytOC to TSOC (total soil organic carbon), and PhytOC storage, making it one of the crucial factors influencing the accumulation of soil PhytOC in the bamboo forests. 

“The potential for soil PhytOC accumulation in bamboo forests of southwest China is substantial, particularly in karst bamboo forests, which can play a significant role in achieving carbon neutrality. The results hold great significance in further elucidating the driving mechanism of PhytOC sequestration and accumulation in bamboo forests and accurately estimating their phytolith carbon sink potential.”