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Phytolith carbon (C) sequestration plays a key role in mitigating global climate change at a centennial to millennial time scale. However, previous estimates of phytolith‐occluded carbon (PhytOC) storage and potential in China's grasslands have large uncertainties mainly due to multiple data sources. This contributes to the uncertainty in predicting long‐term C sequestration in terrestrial ecosystems using Earth System Models. In this study, we carried out an intensive field investigation (79 sites, 237 soil profiles [0–100 cm], and 61 vegetation assessments) to quantify PhytOC storage in China's grasslands and to better explore the biogeographical patterns and influencing factors. Generally, PhytOC production flux and soil PhytOC density in both the Tibetan Plateau and the Inner Mongolian Plateau had a decreasing trend from the Northeast to the Southwest. The aboveground PhytOC production rate in China's grassland was 0.48 × 106 t CO2 a–1, and the soil PhytOC storage was 383 × 106 t CO2. About 45% of soil PhytOC was stored in the deep soil layers (50–100 cm), highlighting the importance of deep soil layers for C stock assessments. Importantly, the Tibetan Plateau had the greatest contribution (more than 70%) to the PhytOC storage in China's grasslands. The results of multiple regression analysis indicated that altitude and soil texture significantly influenced the spatial distribution of soil PhytOC, explaining 78.1% of the total variation. Soil phytolith turnover time in China's grasslands was mainly controlled by climatic conditions, with the turnover time on the Tibetan Plateau being significantly longer than that on the Inner Mongolian Plateau. Our results offer more accurate estimates of the potential for phytolith C sequestration from ecological restoration projects in degraded grassland ecosystems. These estimates are essential to parameterizing and validating global C models. [ABSTRACT FROM AUTHOR]

Terrestrial biogeochemical carbon (C) sequestration is coupled with the biogeochemical silicon (Si) cycle through mechanisms such as phytolith C sequestration, but the size and distribution of the phytolith C sink remain unclear. Here, we estimate phytolith C sequestration in global terrestrial biomes. We used biome data including productivity, phytolith and silica contents, and the phytolith stability factor to preliminarily determine the size and distribution of the phytolith C sink in global terrestrial biomes. Total phytolith C sequestration in global terrestrial biomes is 156.7 ± 91.6 Tg CO 2 yr − 1 . Grassland (40%), cropland (35%), and forest (20%) biomes are the dominant producers of phytolith-based carbon; geographically, the main contributors are Asia (31%), Africa (24%), and South America (17%). Practices such as bamboo afforestation/reforestation and grassland recovery for economic and ecological purposes could theoretically double the above phytolith C sink. The potential terrestrial phytolith C sequestration during 2000–2099 under such practices would be 15.7–40.5 Pg CO 2 , equivalent in magnitude to the C sequestration of oceanic diatoms in sediments and through silicate weathering. Phytolith C sequestration contributes vitally to the global C cycle, hence, it is essential to incorporate plant-soil silica cycling in biogeochemical C cycle models. [ABSTRACT FROM AUTHOR]

Highlights: [•] A recent found persistent carbon sink is C occluded within plant phytoliths. [•] The Chinese cropland phytolith C sink contributes 18% of world's croplands. [•] The predominant phytolith producing crop species were rice, wheat and corn. [•] The sink has doubled since 1978 due to fertilizer application and irrigation. [•] Management practices may further enhance the cropland phytolith C sink. [ABSTRACT FROM AUTHOR]

The persistent terrestrial carbon sink regulates long-term climate change, but its size, location, and mechanisms remain uncertain. One of the most promising terrestrial biogeochemical carbon sequestration mechanisms is the occlusion of carbon within phytoliths, the silicified features that deposit within plant tissues. Using phytolith content-biogenic silica content transfer function obtained from our investigation, in combination with published silica content and aboveground net primary productivity ( ANPP) data of leaf litter and herb layer in China's forests, we estimated the production of phytolith-occluded carbon (PhytOC) in China's forests. The present annual phytolith carbon sink in China's forests is 1.7 ± 0.4 Tg CO2 yr −1, 30% of which is contributed by bamboo because the production flux of PhytOC through tree leaf litter for bamboo is 3-80 times higher than that of other forest types. As a result of national and international bamboo afforestation and reforestation, the potential of phytolith carbon sink for China's forests and world's bamboo can reach 6.8 ± 1.5 and 27.0 ± 6.1 Tg CO2 yr−1, respectively. Forest management practices such as bamboo afforestation and reforestation may significantly enhance the long-term terrestrial carbon sink and contribute to mitigation of global climate warming. [ABSTRACT FROM AUTHOR]

Among the most promising approaches of long-term atmospheric CO2 sequestration is terrestrial biogeochemical carbon sequestration. One of the most promising terrestrial biogeochemical carbon sequestration mechanisms is the occlusion of carbon within phytoliths, the silicified features that deposit within plant tissues. Using phytolith content-biogenic silica content transfer function obtained from our investigation, in combination with published silica content and above-ground net primary productivity ( ANPP) data of China's grasslands, we estimated the production of phytoliths and phytolith-occluded carbon ( PhytOC) in grasslands. The results show that the average above-ground phytolith production rates of China's grasslands (10.9 106 t yr−1 or 1.45% of world grasslands) are much lower than those of other grasslands (e.g. North American nonwoody grasslands) mainly because of much lower ANPP. Assuming a median content of PhytOC of 1.5%, the average above-ground PhytOC production rates of China's grasslands and world grasslands are estimated to be 0.6 106 t CO2 yr−1 and 41.4 106 t CO2 yr−1, respectively. The management of grasslands to maximize ANPP has the potential to result in considerable quantities of phytoliths and securely bio-sequestered carbon. [ABSTRACT FROM AUTHOR]

Among the most promising approaches of long-term atmospheric CO2 sequestration is terrestrial biogeochemical carbon sequestration. One of the most promising terrestrial biogeochemical carbon sequestration mechanisms is the occlusion of carbon within phytoliths, the silicified features that deposit within plant tissues. Using phytolith content-biogenic silica content transfer function obtained from our investigation, in combination with published silica content and above-ground net primary productivity ( ANPP) data of China's grasslands, we estimated the production of phytoliths and phytolith-occluded carbon ( PhytOC) in grasslands. The results show that the average above-ground phytolith production rates of China's grasslands (10.9 106 t yr−1 or 1.45% of world grasslands) are much lower than those of other grasslands (e.g. North American nonwoody grasslands) mainly because of much lower ANPP. Assuming a median content of PhytOC of 1.5%, the average above-ground PhytOC production rates of China's grasslands and world grasslands are estimated to be 0.6 106 t CO2 yr−1 and 41.4 106 t CO2 yr−1, respectively. The management of grasslands to maximize ANPP has the potential to result in considerable quantities of phytoliths and securely bio-sequestered carbon. [ABSTRACT FROM AUTHOR]