土壤有机碳矿物固持机制及其影响因素

Mechanisms and influencing factors of soil organic carbon sequestration by minerals

  • 摘要: 土壤碳库是陆地生态系统的最大碳库, 其在碳循环中起到重要作用。考虑到温室效应的日益严重, 增加土壤有机碳的稳定性成为迫在眉睫的问题。研究证实, 矿物吸附机制是最重要的土壤有机碳稳定机制之一。矿物吸附有机碳容量和稳定性受多重因素影响。土壤矿物类型、结晶程度和径级大小等矿物因素影响矿物吸附能力和机制。非晶质矿物如水铝英石和伊毛缟石对有机碳有很强的吸附能力。植物源碳多被粗径级矿物吸附, 微生物碳则易被细径级矿物吸附。微生物途径形成的微生物碳富集在微生物“热点”地区, 即矿物表面孔隙。微生物降解对矿物结合有机碳的形成有双重作用, 一方面微生物和矿物竞争活性有机碳, 部分矿化成CO2释放到大气中, 部分转化为微生物生物量被微生物循环利用或被矿物吸附。另一方面, 微生物分解惰性有机碳, 使其更易被矿物吸附。除上述因素外, 土壤物理性质、化学性质和土地利用等因素均影响矿物吸附能力。矿物在土壤碳储中的地位毋庸置疑, 研究矿物吸附有机碳机制和因素, 有助于增加土壤碳储量。本文对以往土壤碳研究中与矿物有关的内容进行了总结归纳, 旨在推断矿物保护土壤有机碳相关规律, 为增加土壤碳储量、缓解气候变暖对土壤碳储影响提供理论基础。

     

    Abstract: Soils, which play an active role in the global carbon cycle, are the largest store of carbon in terrestrial ecosystems. Considering the increasing seriousness of the greenhouse effect, it is of utmost importance to enhance the stability of organic carbon in soil. Previous studies have verified that mineral sorption is one of the most significant organic carbon stabilization mechanisms. The capacity and stability of the organic carbon adsorbed by minerals are affected by multiple factors. Soil mineral type, crystallinity, and mineral particles sizes affect the mineral adsorption capacity and mechanism. Amorphous phase minerals such as allophane and imogolite have a strong adsorption capacity for organic carbon. It is widely accepted that plant-derived carbon is preferentially adsorbed by coarse minerals and microbial-derived carbon is strongly adsorbed by fine minerals. This is because microbial-derived mineral-associated organic carbon formed by microbial pathways is enriched in areas of microbial “hot spots”, namely mineral surface pores. Microorganism degradation of soil organic carbon has a dual effect on the formation of mineral-bound organic carbon. On one hand, microorganisms and minerals compete for reactive organic carbon; thereafter, one part of the carbon is mineralized into CO2, and the other part is converted into microbial biomass carbon, which is recycled by microorganisms or adsorbed by minerals. On the other hand, microorganisms degrade resistant organic carbon, and as a result, partially processed organic carbon is more easily adsorbed by minerals. The assimilation of plant-derived carbon into microbial biomass carbon is an important precursor for soil organic carbon stabilization. Microbial degradation of soil organic carbon reduces the molecular size of biomolecules and adds oxygen-containing functional groups to soil organic carbon, both of which are essential for mineral adsorption of organic carbon in the soil. Besides the aforementioned factors, soil physical and chemical properties and land use affect the mineral adsorption capacity. It is indisputable that the mineral adsorption mechanism plays an important role in soil organic carbon storage. It is beneficial to increase organic carbon storage in the soil to study the mechanism and factors of mineral adsorption of soil organic carbon. We have summarized previous studies related to soil organic carbon and soil minerals. The objectives of this study were to explore the correlation law of mineral immobilization of organic carbon in the soil and to provide a theoretical basis for increasing soil organic carbon storage and for mitigating the effects of climate warming on soil organic carbon storage.

     

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