中文摘要：

以浙江慈溪滨海沉积物上发育的5个具有不同植稻年龄的水耕人为土剖面为研究对象,系统分析了土壤中的植硅体及其闭留碳的演变特征。结果表明,水耕人为土时间序列土壤中植硅体的含量变幅为3.67~17.51 g kg-1。水耕人为土中植硅体的剖面分布特征与有机碳相似,呈现出随着土壤深度的增加含量逐渐降低的趋势。其剖面分布特征表明植硅体在水耕人为土中不易移动。与起源土相比,水耕人为土表层植硅体含量有较大程度的增加,说明植稻有利于植硅体在土壤表层富集。而植硅体随植稻年龄的增加没有表现出有规律的增加或减少趋势。统计分析表明植硅体和总硅之间呈极显著正相关,说明植硅体对土壤发生中的硅循环起着重要作用。水稻产生的植硅体其体内闭留的碳量较高,但由于土体内植硅体总量较低,植硅体闭留碳仅占总有机碳的0.93%~1.68%。现有数据表明,仅通过根系与残茬返还土壤,种植富硅植物水稻并不能显著增强土壤的长期固碳能力。由于植硅体固定的碳在土壤环境中比较稳定,如果能强化秸秆还田,植稻对于土壤长期固碳具有意义。

英文摘要：

A Stagnic Anthrosols chronosequence consisting of five profiles derived from calcareous marine sediments with cultivation history from 0 to 1000 years was studied here.The dynamic changes of phytoliths,organic carbon occluded within phytoliths（PhytOC）,total Si（TSi）,and total organic carbon（TOC） were investigated.Results showed that the content of phytoliths in the soils varied widely from 3.67 g kg-1 to 17.51 g kg-1.The profile distribution of phytoliths in soils was similar to that of SOC,as being higher in the surface horizon and decreasing rapidly with depth.The findings implied that the accumulation of phytoliths in topsoil was mainly due to phytoliths release from organic matter during its decomposition.Phytoliths content in surface horizons（roughly 0-16 cm depth） in Stagnic Anthrosols（range from 10.9 g kg-1 to 17.5 g kg-1） was consistently higher than that in uncultivated soil（6.5 g kg-1） and vertical distribution of phytoliths in the lower horizons was generally uniform,suggesting paddy cultivation favored the accumulation of phytoliths in the surface horizon.By comparison of paddy profiles in the chronosequence,it was found that phytoliths in any horizons did not show the increasing or decreasing trend against paddy cultivation age.Significant linear correlations could be found between phytoliths and TSi,indicating that phytoliths played an important role in the Si cycles during paddy soil development.In this study,the proportion of the PhytOC fraction to TOC ranged from 0.93% to 1.68%,indicating that PhytOC was a relatively minor fraction of the soil carbon,which was probably due to the low return ratio of rice straw.