土壤水溶性有机碳（WSOC）C-14分析方法及其在示踪森林土壤剖面WSOC来源中的应用

Soil water-soluble organic carbon (water-soluble organic carbon, WSOC) is the most active, labile carbon in the soil organic carbon pool. It is very sensitive to changes of environmental factors. Therefore, it is an important object to learn the change of the "source" and "sink" between soil organic carbon pool and atmospheric carbon pool under the global change. It is available from a variety of sources, from the surface litter, humus soil, root exudates, also from the modern microorganism. Different sources of response to changes of environmental factors are not the same. Radiocarbon (14C) tracing is one of the effective methods to indicate the main source of soil WSOC. However, using the traditional method of WSOC extraction for 14C measurement has problem in the accuracy of radiocarbon because of the involution of containminants during the experiment. Based on this, the project palns to insert one of the 14C modern carbon standards, sucrose standard through the process of soil WSOC extraction to calibarate the 14C pollution. Using this method will provide a guarantee for the accurate measurement of 14C in soil WSOC. The project will aplply the improved method to measure the 14C content of WSOC in a soil profile in Dinghushan Bioshpere, and to reveal the relationship between changes of the main source and content of soil WSOC and environmental factors in different seasons.

土壤水溶性有机碳（water-soluble organic carbon ，WSOC）是土壤有机碳库中最活跃、最易分解的有机组分。它对环境因子变化极为敏感，是研究全球变化下土壤有机碳库与大气碳库之间“源”/“汇”变化的重要对象。土壤WSOC来源多样，既来源于地表落叶，土壤腐殖质，根系分泌物，也来源于现代微生物，不同来源对环境因子变化的响应不一样。放射性碳（14C）示踪是揭示土壤WSOC主要来源的有效方法之一。然而，传统提取WSOC的方法由于存在污染，WSOC的14C值可能受到不同程度的影响。基于此，项目通过在提取土壤WSOC流程中插入14C现代碳标准之一的蔗糖标准，消除实验带入的14C污染，为精确测量土壤WSOC 14C值提供保证。运用改进后的方法，项目拟开展鼎湖山森林土壤剖面中WSOC 14C测量工作，揭示不同季节下森林土壤WSOC的主要来源和含量变化与环境因子之间的关系。

土壤水溶性有机碳（water-soluble organic carbon ，WSOC）是土壤有机碳库中最活跃的有机组分，是陆地碳向海洋输送的主要形式，也是表层碳向深部迁移的主要形式，它对研究全球碳循环以及全球变化变化至关重要。项目开展了鼎湖山常绿阔叶林土壤水溶性有机碳（WSOC）AMS-14C制样技术与WSOC剖面迁移示踪的研究。主要结论如下：1）针对深部土壤WSOC含碳量较低，开展了15-100微克碳的小样品制样方法研究，保障了低WSOC含量AMS-14C数据的可靠性；2）开创了湿化学法高温氧化WSOC的方法，该方法流程简洁，效率高，带入外界污染低，准度与精度和传统的UV氧化法几乎一致； 3）常绿阔叶林剖面土壤中WSOC含量由表及深逐渐降低， FM值变化幅度为1.04 —1.00，与表层0-10 cm土壤有机碳很接近， WSOC主要来源于表层0-10 cm土壤有机碳的分解，更新速率在年尺度，表层有机碳可以以WSOC的形式进入深部土壤，可能为深部土壤微生物活动输入必需的营养物质，这会导致深度土壤微生物活性增强，减弱土壤固碳能力，增加土壤向大气CO2的排放。5）常绿阔叶林剖面土壤CO2气体的14C（FM）值较2007年采集时有了明显下降，但仍高于目前大气CO2 14C的FM值，与WSOC值接近，表明土壤CO2气体可能主要来源于表层近十年来植物残体分解产生的有机碳。