在植物固定的有机碳中，植硅体闭蓄有机碳（简称植硅体碳PhytOC)可长期存留于土壤，对减缓大气CO2浓度增加具有重要意义。生态系统中植硅体碳的生产、周转和增碳潜力正成为全球变化研究的一个重要方面。草原生态系统面积辽阔，增碳潜力巨大，但对草原植硅体固碳的研究目前只有依据植物地上生产力及其植硅体碳平均含量而做的粗略估算。草原地上部分植硅体碳测定不足，地下部分完全忽略；不同土地利用对植硅体碳生产的影响尚无研究。基于草原地下生产力是地上生产力约十倍的事实和人为利用对草原植物组成和生产力的影响，我们推测草原植物地下生产是植硅体碳生产的主要部分，草原利用将降低植硅体碳的生产。本项目选择我国主要草原类型，通过测定其在天然、退化和开垦状态下植物地上与地下生产力及其植硅体碳含量以及土壤植硅体碳含量，计算草原植硅体碳生产通量，评价草地利用对土壤碳库的长期影响，为草原碳汇计算和草原增碳措施制定提供理论依据。

Phytolith-occluded carbon (PhytOC) is an inert form of organic carbon that is bio-sequestered within plants and accumulated in soils after plant decomposition. As phytOC has a long residual time in soil (on a millennial scale), it pays an important role in carbon bio-sequestration from a long-term perspective, which can off-set the increase in atmospheric carbon dioxide concentration. The phytOC production and turnover rate as well as its potential in carbon sequestration has recently emerged as a focus in the search for the methods to mitigate the climate change...The grassland ecosystems cover about one fifth of the world's land surface, and have a great potential for carbon sequestration. However, the research on the phytOC production in grassland is very limited, with only some rough estimation of phytOC production based on the above-ground net productivity (ANPP) and the mean phytOC content of major plant species in grasslands. The phytOC content and production has not yet been sufficiently determined in grassland plant shoots (ANPP), and not at all evaluated in grassland plant roots (BNPP, below-ground net productivity). In addition, the impacts of grassland use, such as animal grazing and crop cultivation, on phytOC production has not yet been assessed. As the BNPP is generally around 10-times greater than the ANPP in semi-arid grassland, and the grassland use has profound impats on grassland species composition (which has different phytOC content) and productivity, we speculate that grassland BNPP has a.significant contribution to total phytOC production in grassland, and that land use through animal grazing and crop cultivation reduces grassland phytOC production...In present project, we will determine the ANPP, BNPP and the phytOC production of major plant species of the main grassland vegetation types in Inner Mongolia under three contrast conditions: intact natural, grazing degraded and under reclamation, and measure the total organic carbon and phytOC content in soil profiles. Thus we can (1) determine total phytOC production rate under varying conditions, and establish the relations between phytOC production and climate and soil factors; (2) upscale the results at the representative grassland sites to grassland regions to quantify the carbon sequestration potential via phytOC production in grassland regions, and (3) evaluate the long-term effects of land use change on soil carbon storage for the development of grassland management systems.