Study On The Relationship Between The Phytolith-occulded Carbon Accummulation In Dominant Plants And Environmental Factors In The Typical Steppe Of Inner Mongolia

Phytoliths may occlude 1-6% organic carbon,known as phyt OC.Phytoliths are highly resistant to high temperature and corrosion,thus the phytolith-occluded organic carbon may be preserved in soils and sediments for thousands of years.The occlusion of carbon within phytoliths has recently been shown to be an effective biogeochemical mechanism for long-term carbon sequestration,contributing to the mitigation of climate change.Grassland is one of most widely distributed terrestrial ecosystems.The dominant plants in grasslands,especially grasses and sedges are rich in silicon(Si),and have high content of phytoliths.However,the phyt OC concentration of grassland plants has not been largely determined,and the relationships between the phyt OC concentration and environmental factors not been explored.Here we determined the phyt OC concentration of the dominant plants under different environmental conditions in the typical steppe region of Inner Mongolia,China,with the aims to understand the accumulation rules of phyt OC in plants,and to explore the relationships between phyt OC concentration and environmental factors.This study will provide new data and contribute to define the method to estimate the long-term carbon sequestration potential of phyt OC production in grasslands.We collected plant(the aboveground parts of dominant species)and soil samples,and determined the phytolith and phyt OC concentrations in plants,and available silicon content in soils along with other soil physiochemical properties across different environments,including the grasslands on basaltic or granite parent materials,grasslands under different levels of water addition,and in grazing versus non-grazing grassland paddocks.The results showed that(1)The soil on the basaltic parent materials(i.e.,in basaltic region)had higher available silicon(Si)content than that on granite parent materials(i.e.,in granite region).However,the phytolith concentration of Stipa grandis was significantly lower in basaltic than in granite regions.Considering all plant species in measurement,we did not detect a significant difference in phytolith and phyt OC concentrations between the basaltic and granite regions.(2)The phytolith concentration and phyt OC concentration at steppe community level were higher under a treatment of 50% water addition(T2: +50% of natural precipitation)than under the control(natural precipitation)or a treatment of 25% water addition.It indicated that that the enhancement of water addition to plant transpiration was greater than that to biomass accumulation,thus increased the phytolith production per unit biomass production.(3)The phytolith and phy TOC concentration of plants in grazed grassland increased with the season(June,July and August),for example,the phytolith concentration in Leymus chinensis and Stipa grandis were significantly higher in August than in July(P<0.05).It suggests that plant sampling for determination of phytolith or phyt OC production should be done at the end of plant growing season,not early.Meanwhile,the phyt OC concentration of Stipa grandis and Cleistogenes squarrosa in animal consumed parts(above 6cm in height)was greater than those in whole plants in the enclosed non-grazing grassland.The fate of the phyt OC in forage consumption of grazing animals needs to be further studied.There was a significant positive correlation between phytolith concentration and phyt OC concentration(P<0.01)across all the environmental conditions,suggesting that the changes in environmental factors or management measures that promote plant silicon uptake would enhance phyt OC production.Our study improved the understanding of the mechanisms underlying phyt OC accumulation,and provides the basis for plant sampling and analysis for estimation of the phyt OC production potential for long-term carbon sequestration.