Search

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]

Abstract: The coupled terrestrial biogeochemical cycles of silicon (Si) and carbon (C) that are driven by plant action play a crucial role in the regulation of atmospheric CO2. Generally, the processes involved in the coupled cycles of Si and C include plant-enhanced silicate weathering, phytolith formation and solubilization, secondary aluminosilicate accumulation, phytolith occlusion of C as well as physico-chemical protection of organic C in soils. There is increasing evidence of biological pumping of Si in terrestrial ecosystems, suggesting that complex feedbacks exist amongst the processes within the coupled Si and C cycles. Recent advances in the coupled Si and C cycles offer promising new possibilities for enhancing atmospheric CO2 sequestration. Organic mulching, rock powder amendment, cultivating Si-accumulating plants and partial plant harvesting are potential measures that may allow for long-term manipulation and biogeochemical sequestration of atmospheric CO2 in soil–plant systems. [Copyright &y& Elsevier]

Grasslands play a crucial role in the coupled biogeochemical cycles of carbon (C) and silicon (Si) because they have a large biogenic Si pool (i.e. phytoliths). In recent decades, desertification has occurred extensively in sandy grasslands due to human activities and to increased aridity as a consequence of climate change. The present study determined the contents of phytoliths and C occlusion within phytoliths (PhytOC) in sandy grassland with different vegetation coverage from eastern Inner Mongolia, China and preliminarily assessed the effects of desertification on phytoliths and PhytOC production. Our results showed that the phytolith and PhytOC contents among different plant species varied from 0.68 to 9.23% and 0.03 to 1.13‰, respectively. However, the community-weighted means of the phytolith and PhytOC contents for the total aboveground vegetation were only 1.13–3.61% and 0.09–0.35‰, respectively, and their respective production fluxes ranged from 8.94 to 47.8 kg ha −1  year −1 and from 0.06 to 0.48 kg ha −1  year −1 , respectively. As desertification progressed, the total contents of phytoliths and PhytOC in aboveground vegetation did not change significantly, whereas the production fluxes of phytoliths and PhytOC were markedly reduced. This study indicates that grassland desertification decreases the range of the total contents of phytolith and PhytOC by reducing species richness, and decreases the production fluxes of phytoliths and PhytOC by reducing aboveground biomass. Grassland restoration can theoretically enhance the production fluxes of phytoliths and PhytOC ~ five-fold. [ABSTRACT FROM AUTHOR]