土壤有机碳初始积累过程及深度分异研究

土壤有机碳（SOC）循环及周转规律是土壤碳汇研究的一个基本理论,然而当前对SOC的初始积累过程及其深度分异机制并不明确。以安塞纸坊沟刺槐林为实验地,对20、40、60 cm 3个深度,均匀添加枯落物碎屑的土壤培养坑分3、7和11月进行1年期的培养和观测。结果表明：20和40 cm深度7月SOC、活性有机碳（POC）及总氮（TN）值最高,11月各指标含量回落,可溶性有机碳（DOC）和可溶性有机氮（DON）呈相反变化趋势。培养过程中各指标出现深度分异：与20 cm不同,在60 cm深度,SOC随培养过程而递减,POC及全氮递增,而DOC在7月出现高值。各指标相关分析表明,随深度增加,SOC与DOC、DOC与全N相关程度增强。SOC在初始积累过程中先增后减,体现出自我调节机制的存在。DOC在浅层和深层表现出异源特点,培养坑60 cm深度SOC来源出现多元化,枯落物腐解产物影响程度减弱。

A study on initial SOC accumulation and depth distribution

Rules of soil organic carbon （SOC） cycles is a basic theory for the study on soil carbon pool. However, the initial accumulation process and depth distribution of SOC are still not clearly known. In this study, we have observed the dynamics of SOC and its relative factors in incubation holes of three depths （20, 40, 60 cm）, which were backfiUed by mixture of soils and litter rags sampled from Robinia pseudoacacia forest in Ansai County, China, and took samples respectively in March, July and November, 2010. For samples with the depths of 20 cm and 40 cm, the values of SOC, POC, TN are highest in July but decrease in November, with a inverse states for DOC. Different from that of the 20 cm sample, the SOC value of the 60 cm sample decreases gradually in the process of incubation and the values of TN and POC have increase trends, DOC appears a high value in July. The correlations between SOC and DOC, DOC and TN increase with the increase of the depth of samples. During C accumulation, the SOC value increases at the beginning but decreases later, showing a self-modulation function. The DOC values show different sources in various soil layers, the SOC value suggests complex sources at 60 cm depth, where the production of litters decomposition has a limited effect.