Abstract: Phytolith-occluded organic carbon (PhytOC) sink is an important component of grassland carbon sink. In this study, we extract phytoliths by Walkley-Black type, from Poaceae community, Asreraceae community and Cyperaceae community in Songnen grassland. PhytOC was measured by alkali dissolution spectrophotometry. PhytOC content of phytoliths, PhytOC content of biomass and phytolith content were calculated. We estimated the rate of PhytOC sequestration based on the amount of PhytOC in Songnen grassland and analyzed the differences in capacity of PhytOC sequestration among those three communities. The results showed that the average rate of PhytOC sequestration in Songnen grassland was 1.67 t CO₂·hm^-2·a^-1. There was a significant negative correlation between phytolith content and PhytOC content of phytoliths (P<0.05, R²=0.94). The capacity of PhytOC sequestration varied among different communities, with 2.151 kg CO₂·hm^-2·a^-1 for Cyperaceae community, 1.716 kg CO₂·hm^-2·a^-1 for Poaceae community, and 1.218 kg CO₂·hm^-2·a^-1 for Asreraceae community. PhytOC sequestration was affected by community composition, aboveground net primary productivity, and the formation processes of phytoliths. Our results could enrich the basis for studying grassland carbon cycling.

Key words: sustainable development., resource, metabolism