深层土壤有机碳的来源、特征与稳定性

Sources,Characteristics and Stability of Organic Carbon in Deep Soil

深层土壤有机碳占土壤剖面总有机碳的一半以上.最近发现表层和深层土壤有机碳动态及其调控因素并不相同,这对准确评估土壤固碳潜力具有重要影响.深层土壤有机碳主要来源于根系、根系分泌物、可溶性有机碳、土壤微生物及生物扰动作用,这些来源的相对重要性可能取决于气候、土壤、植被类型和土地利用方式;与表层土壤相比,深层土壤有机碳一般具有较高的稳定性同位素C/N、平均驻留时间长、矿化速率低和高稳定性.深层土壤有机碳的生物化学稳定性、化学稳定性和物理保护三种稳定性机制的相对贡献并不清楚.未来应加强环境变化和人类干扰对深层土壤有机碳动态及稳定性影响的研究.

Organic carbon stored in deep soil generally contributes to more than half of the total stocks within a soil profile. Recent studies suggest that carbon dynamics and regulatory mechanisms may be differences for topsoil and deep soil, so it is important to the evaluation of soil carbon sequestration po- tential. Four main sources of organic matter input into deep soil include root litter and root exudates, dissolved organic carbon, soil microbial biomass and bioturbation, the relative importance of these sources may depend on climate, soil, vegetation type as well as land-use. In contrast to topsoil, organ- ic carbon stored in deep soil horizons generally is characterized by much higher stable isotope C/N rati- os, high mean residence times, low mineralization rate and high stability. The relative contribution a- bout the biochemical stabilization, chemical stabihzation and physical protection of organic carbon in deep soil is not clear. In future we should put more emphasis on the research about the effects of envronment change and human disturbances on dynamics and stability of organic carbon in deep soil.