黄土高原次生植被自然恢复中土壤碳固持及其物理化学稳定性机制

Soil organic carbon (SOC) is an essential part of physical-chemical properties in soil, and the most important indicator of soil quality. It’s stabilization is crucial for carbon sequestration assessment under the vegetation restoration. However, most of studies have focused on the quality and stabilization of SOC in upper soils (0-30 cm), and less information has focused on that in the deeper soils.This study took a natural secondary vegetation restoration sequence (~160 yr) in the Ziwuling forest region on the Loess Plateau as the research object. Through defining soil aggregate classes and isolating soil C fractions of soil profile in different stages of vegetation restoration, as well as the application of synchrotron radiation soft X-ray spectroscopy to qualitative and semi-quantitative analyze the SOC chemical structure. The objectives of the study were to: study the dynamics of soil SOC and its fractions, as well as the time stability of the SOC in the process of long-term vegetation restoration, reveal the coupling mechanism between soil physi-chemical composition and carbon sequestration benefit; explore the dynamic process of SOC structure characteristics in long-term process of vegetation restoration; examine the pathway of SOC fixed between the fractions of SOC and the dynamic of the chemical structure; clarify the effects mechanism of SOC distribution, density composition and soil aggregate on the structure of SOC, reveal the effect mechanism of long-term vegetation restoration on the physical and chemical stability of soil SOC. So as provide a new basis to further study on soil carbon sequestration and its stability mechanism in the process of vegetation restoration.

土壤有机碳（SOC）是土壤最基本的要素，且是土壤质量的重要指示因子，其稳定性对植被恢复下土壤固碳效益评估具有重要作用。以黄土高原次生植被自然恢复序列（~160 年）为研究对象，通过对不同恢复阶段土壤剖面团聚体颗粒分级以及对SOC密度组分进行区分，以及应用同步辐射软X-射线光谱技术对SOC进行化学结构的定性和半定量分析，研究SOC以及其组分在长期恢复过程中的动态变化及其时间稳定性，揭示SOC理化组成与固碳效益间耦合机制；探讨长期植被恢复过程中SOC结构动态变化过程，研究长期植被恢复过程中SOC固定在有机碳组分间分配、转化以及化学结构的动态变化特征，阐明SOC分布、密度组分和土壤团聚体联结关系对SOC结构影响机制，揭示长期植被恢复对SOC影响的物理化学稳定性机制。以期为进一步研究植被恢复过程中土壤固碳特征及其稳定机制提供新的依据。

土壤有机碳（SOC）是土壤最基本的要素，且是土壤质量的重要指示因子，其稳定性对植被恢复下土壤固碳效益评估具有重要作用。以黄土高原次生植被自然恢复序列（~160 年）为对象，研究了SOC以及其组分在长期恢复过程中的动态变化及其时间稳定性，探讨了长期植被恢复过程中新碳和老碳的动态变化过程，阐明了SOC和土壤团聚体的联结关系，揭示了长期植被恢复对SOC影响的物理化学稳定性机制，主要取得如下研究进展：1）发现长期植被恢复（~160年）后，表层和下层的SOC分别提高了219%和37%，且表层SOC曾显著的线性增加，而下层SOC表现出先增加后趋向稳定的变化特征；2）明确了土壤总有机碳增加速率随着植被恢复的增加而降低，发现植被恢复中新碳的比例逐渐增加，相反，老碳的比例逐渐降低，大约恢复30年左右，土壤中新碳和老碳的比例基本相等；3）发现新碳的量主要由凋落物和细根的输入决定，而且SOC固定后期受氮限制的影响，但新碳的增加速率和SOC的分解速率主要由土壤结构决定；4）阐明了植被恢复能够显著增加土壤团聚体中活性碳和有机碳含量，土壤团聚体的物理保护作用是SOC固定的重要机制之一；5）研究揭示了SOC的稳定性在表层土壤中主要是由植物和微生物决定的生物化学稳定机制决定，而在下层土壤中主要受土壤结构和质地等的物理保护机制影响。研究可为进一步研究植被恢复过程中土壤固碳特征及其稳定机制提供新的理论依据。