Abstract:

The calcareous soil was widely distributed in Guangxi, and its high carbonate content can affect the material cycling in the soil. In order to clarify the influence of carbonate content in calcareous soil on the mineralization of organic carbon in soil straw, the experiment of adding exogenous straw to soil was carried out. The treatments of no addition control (CK), with addition of 5% straw (C0), 5% straw+5% calcium carbonate (C1), 5% straw+15% calcium carbonate (C2) and 5% straw+25% calcium carbonate (C3) were set up respectively to study the relationship between the transformation of exogenous straw organic carbon in calcareous soil and the content of soil calcium carbonate. Compared with the control, the rate of CO₂ release, cumulative release and active organic carbon content of soil were significantly increased after adding straw. During the incubation period, the soil CO₂ release rate of each treatment showed a rapid decrease in the early stage (2-5 d), a slow decrease in the middle stage (5-39 d), and a stable trend in the late stage (39-60 d). The treatments with the addition of calcium carbonate increased the cumulative release of soil CO₂ by 5.10%-15.69%, but the release rate and cumulative release of soil CO₂ in C3 treatment were lower than those in C1 and C2 treatments, and showed a strong negative excitation effect on soil organic carbon mineralization, up to 183.33%. Soil microbial biomass carbon (MBC) content gradually decreased with the increase of soil calcium carbonate content. Soil calcium carbonate could promote the increase of soil dissolved organic carbon (DOC). Compared with C0, the DOC content of C1 treatment increased by 106.35%. Correlation analysis showed that the contents of soil MBC and DOC were significantly positively correlated with the cumulative release of soil CO₂(P<0.01). In addition, there was a significant positive correlation between the contents of soil MBC and DOC (P<0.05).

Key words: calcareous soil, calcium carbonate, straw, organic carbon mineralization, activated organic carbon

摘要：

广西石灰性土壤面积较广，其较高碳酸盐含量能够影响土壤中物质循环。为了明确石灰性土壤中碳酸盐含量对土壤秸秆有机碳矿化过程的影响，加深对石灰性土壤有机碳的周转与固存机制的认识，开展了土壤外源秸秆添加培养试验，分别设置无添加对照（CK）、添加5%秸秆（C0）、5%秸秆+5%碳酸钙（C1）、5%秸秆+15%碳酸钙（C2）和5%秸秆+25%碳酸钙（C3）处理，以研究石灰性土壤中外源秸秆有机碳的转化与土壤碳酸钙含量的关系。结果表明，与对照相比，添加秸秆后土壤CO₂释放速率、累积释放量、活性有机碳含量均得到大幅提升。培养期间，各处理土壤CO₂释放速率均表现为前期（第2—5天）快速下降、中期（第5—39天）缓慢下降、后期（第39—60天）趋于稳定。不同碳酸钙处理使土壤CO₂累积释放量提升了5.10%—15.69%，但C3处理的土壤CO₂释放速率、累积释放量均低于C1和C2处理，并对土壤有机碳矿化表现出强烈负激发效应，最高为183.33%。随着土壤碳酸钙含量的增加，土壤微生物生物量碳（MBC）含量逐渐降低。土壤碳酸钙能够促进土壤溶解性有机碳（DOC）含量增加，与C0相比，C1处理DOC含量提高了106.35%。相关分析表明，土壤CO₂累积释放量和土壤MBC、DOC含量均呈极显著正相关（P<0.01），土壤MBC含量和DOC含量呈显著正相关关系（P<0.05）。

关键词: 石灰性土壤, 碳酸钙, 秸秆, 有机碳矿化, 活性有机碳