喀斯特地区黄壤和石灰土剖面土壤水溶性有机碳和易氧化态碳的比较研究

Labile organic carbon in limestone soil and yellow soil in karst areas,Southwest China

土壤水溶性有机碳（SWOC）浓度和通量是土壤环境变化的敏感指标, 可反映环境条件的变化, 是土壤微生物活动能源和土壤养分的驱动力。本研究以喀斯特地区两种典型的土壤, 即石灰土和黄壤剖面为研究对象, 通过测定土壤属性、有机碳和活性有机碳的空间分布, 探讨了喀斯特地区石灰土和黄壤有机碳（SOC）和活性有机碳动态变化及影响因素。研究结果显示：土壤有机碳含量变化规律为黑色石灰土＞黄壤, 黄色石灰土与黄壤差异不明显；土壤水溶性有机碳（SWOC）含量变化为黑色石灰土＞黄壤＞黄色石灰土, 百宜黄壤乔木林剖面土壤水溶性有机碳占总有机碳的比率最高, 达0.040%（25℃）和0.527%（70℃）, 清镇黑色石灰土剖面最低, 仅0.016%（25℃）和0.255%（70℃）；五个剖面冷水（25℃浸提）土壤水溶性有机碳与土壤总有机碳含量间的相关性以及热水（70℃浸提）土壤水溶性有机碳与土壤总有机碳间的相关性均达极显著水平；石灰土易氧化态碳（SROC）含量大于黄壤剖面, 不同土壤剖面易氧化态碳占总有机碳的比例变化为39.35%～53.95%, 总体上远大于水溶性有机碳占总有机碳的比例。五个典型剖面的土壤水溶性有机碳和易氧化态碳含量在剖面上的分布反映了植物残体的输入及在土壤中的分解累积特征和喀斯特地区剖面侵蚀和土壤成土过程中土壤活性有机碳的动态变化。

The contents and fluxes of SWOC are sensitive indicators of soil environmental changes, energy of soil microbial activity and driving force of soil nutrients, which could reflect the changes in environmental conditions. In this study, limestone soil and yellow soil, typical soils in karst areas of southwest China are studied for their dynamics of soil organic carbon （SOC） and active organic carbon （water-extractable and readily oxidizable organic carbon）. The results show that SOC contents in different soils are different： black limestone soil has higher average SOC content than yellow soil. Similar to SOC, the contents of both cold （25℃） and hot （70℃） water-extractable organic carbon （WEOC） in black limestone soil is also higher than in yellow soils. The percentages of the WEOC in total soil organic carbon are the highest in the yellow soil profile, being 0.040% （25℃） and 0.527% （70℃）, while the WEOC in limestone soil profiles is the lowest, being 0.016% （25℃） and 0.255% （70℃）. The WEOC is significantly correlated to SOC in the five soil profiles studied. The significant differences in readily oxidizable carbon contents （ROC） are found between the limestone soil profiles and yellow soil profiles, showing that the limestone soil profiles have higher ROC than yellow soil profiles. The percentages of the ROC in the total SOC are much larger than those of the WEOC, and are variable in different soil types, ranging between 39.4% and 54.0%. In general, all the active organic carbons, including cold and hot water extractable organic carbon as well as readily oxidizable organic carbon, vary with SOC in a positive relationship. Among the active soil organic carbons, the hot WEOC show clear differences between different soils, and significant relationships with SROC and SOC, which can be accordingly a better indicator of SOC dynamics in soil.