不同培养温度下严重侵蚀红壤的有机碳矿化特征

研究侵蚀土壤有机质矿化及其温度敏感性(Q₁₀)对深入认识水土流失地区土壤有机碳动态变化具有重要意义。该文以福建省长汀县河田镇严重侵蚀区的裸露红壤为研究对象, 通过测定不同培养温度(10 ℃、20 ℃和30 ℃)下的土壤有机碳矿化速率、培养过程中微生物生物量碳(MBC)和可溶性有机碳(DOC)含量的变化, 探讨了温度对严重侵蚀红壤有机碳矿化特征的影响及其Q₁₀。结果表明: 温度对严重侵蚀红壤有机碳矿化具有显著影响, 温度越高土壤有机碳矿化速率和矿化率越高; 培养过程中土壤有机碳累积矿化量与MBC显著正相关, 与DOC极显著负相关, 说明微生物生物量和可利用碳含量显著影响土壤有机碳的矿化。尽管严重侵蚀红壤有机碳含量仅为1.54 g·kg^-1, 但培养180天的土壤有机碳的累积矿化率高达22.2%-33.3%, 表明侵蚀红壤有机碳容易被矿化。严重侵蚀红壤在10-20 ℃时的Q₁₀值为1.41, 20-30 ℃时Q₁₀值下降到1.06, 土壤有机碳质量低是导致Q₁₀值较低的重要原因, 而严重侵蚀区的红壤长期裸露使微生物对高温产生适应性是高温时Q₁₀值接近1的重要原因。因此, 在未来气候变暖的趋势下, 恢复植被覆盖对减少严重侵蚀红壤有机碳矿化损失具有重要意义。

Characteristics of soil organic carbon mineralization at different temperatures in severely eroded red soil

It is crucial to study the soil organic matter decomposition and its temperature sensitivity for in-depth understanding of soil organic carbon (SOC) dynamic changes in severely eroded red soil. We selected the severely eroded red soil on the bare land from Hetian town of Changting County as the research object. To study the influences of temperature on SOC mineralization and their temperature sensitivity (Q₁₀), the SOC mineralization rate, the associated soil microbial biomass carbon (MBC), and dissolved organic carbon (DOC) under different incubation temperatures (10, 20 and 30 °C) were measured. The results showed that the incubation temperature significantly influenced the SOC mineralization. The mineralization ratio and the cumulative SOC mineralization rate increased with temperature. During the incubation period, the cumulative SOC mineralization was positively and significantly correlated with the soil MBC, and negatively correlated with soil DOC, indicating that soil microbes and C availability can significantly influence the SOC mineralization. During the 180 days incubation period, the accumulation mineralization rate of the severely eroded red soil was as high as 22.2%-33.3% under the conditions of the SOC content being only 1.54 g·kg^-1, which indicates that the eroded red soil is easily mineralized. For the severely eroded red soil, its SOC temperature sensitivity (Q₁₀) value was 1.41 at low temperatures (10-20 °C), but decreased to 1.06 at high temperatures (20-30 °C). The relatively low Q₁₀ value at low temperatures was partly attributed to the low soil SOC quality. Furthermore, the long-time exposure to sunshine for the severely eroded red soil in the summer leads to the soil microbial adaptability to high temperature. As a result, its Q₁₀ value is close to 1 at high temperatures. This study implies that it is of great significance to restore vegetation to minimize loss SOC caused by mineralization of the eroded red soil under climate changes in the future.