坡耕地黑土活性有机碳空间分布及生物有效性

Spatial Distribution and Its Biologic Availability of Labile Organic Carbon of Black Soil at Sloping Field

以一东北黑土区典型漫岗坡耕地为研究对象，测定不同侵蚀程度地形部位的活性碳组分，以分析土壤侵蚀对活性碳组分的影响以及沉积区侵蚀碳的归宿。研究结果表明：各地形部位表层黑土（0～20cm）水溶性有机碳（WSOC）含量介于14．6～20．0mg／kg之间，低于总SOC含量的0．15％WSOC在沿坡迁移的同时，向下淋溶也很显著。MBC含量为121．5～583．6mg／kg，占总SOC的1．0%～4．7％。Min—C变化范围为52．8～115．3mg／kg，土壤Min-C差异主要集中在表层。土壤侵蚀显著降低侵蚀部位表层土壤Min-C、WSOC和MBC含量，沉积区土壤MBC、Min—C含量及其商值较高，而WSOC却无显著累积。相关关系表明，表层土壤Min—C、WSOC和MBC均于总SOC含量呈显著正相关。初步的研究结果认为侵蚀物质的输入增加沉积区表层土壤微生物活性和土壤碳的矿化潜力，常年处于氧化环境中的侵蚀碳可能被矿化而难以累积。

A typical rolling farmland in Black Soil region of Northeast China was taken as a case study to analyze the impact of soil erosion on the components of labile soil organic carbon and the fate of eroded carbon in deposition sites based on measurement of labile organic carbon in different geomorphic positions. The results were as follows： （1） Water soluble organic carbon （WSOC） for surface horizon （0～20 cm） ranged from 14. 6 mg/kg to 20.0 mg/ kg and was 0.15% less than total soil organic carbon （TOC） ; The leach of WSOC was significant as it transported along the slope. Microbial biomass carbon （MBC） ranged from 121.5 mg/kg to 583.6 mg/kg, which account for 1.0%～4. 7% of TOC. Mineralizable carbon （Min-C） ranged from 52.8 mg/kg to 115.3 mg/kg, and its difference was focus on surface layer soils. （2） Soil erosion significantly decreased the content of WSOC, MBC and Min-C at eroded geomorphic positions, those of depositional sites such as foot-slope accumulated except for WSOC. The significant positive correlation between WSOC, MBC, Min-C and TOC was found. Above preliminary conclusions demonstrated that eroded carbon trapped in deposition positions increased the activity of microorganism and was apt to be mineralized other than be sequestrated in oxidizing environment.