小浪底库区消落带落干期土壤微生物生物量碳动态变化特征

Dynamic Changes of Soil Microbial Biomass Carbon During the Drying Period of Hydro⁃Fluctuation Belt in the Xiaolangdi Reservoir Area

为了解小浪底库区消落带落干期土壤微生物生物量碳(SMBC)的动态变化特征及其对土壤肥力的影响,利用2018年6—8月265、255、245 m高程以及对照高程(275 m)6期采样点数据,对不同淹水背景下消落带落干期SMBC含量进行分析。结果表明,小浪底库区消落带落干期SMBC含量及其与土壤有机碳(SOC)含量的比值(SMBC/SOC)在同一高程下随时间推移整体呈降低趋势,且上土层(0~10 cm)SMBC含量与SMBC/SOC值均高于下土层(10~20 cm)SMBC含量与SMBC/SOC值,其在土壤垂直深度上表现出较大差异;在不同高程SMBC含量及SMBC/SOC值均差异显著,表现为在245 m高程数值较低,在265、255 m高程数值明显升高并高于275 m高程的数值,表明短期、中期淹水能在一定程度上提高土壤微生物的活性,而长期淹水对土壤微生物的活性产生极大的抑制作用;小浪底库区消落带SMBC含量与土壤含水率呈极显著正相关,与土壤pH值呈显著负相关,与土壤温度、SOC含量、全氮含量显著相关,其变化特征能够揭示微生物活性对消落带土壤肥力的影响。

In order to explore the dynamic change characteristics of soil microbial biomass carbon(SMBC)and its impact on soil fertility during the drying period of hydro⁃fluctuation belt in the Xiaolangdi Reservoir area,the contents of SMBC under different flooding backgrounds were analyzed by using the sampling point data of six samples at 275(control elevation),265,255 and 245 m elevation from June to August 2018.The results show that SMBC and their ratios to soil organic carbon(SOC)(SMBC/SOC)are decreased gradually with time at the same elevation,and they are higher in the upper layer(0-10 cm)than that in the lower layer(10-20 cm).The SMBC and SMBC/SOC are sig⁃nificantly different at different elevations,and are lower at 245 m elevation,but significantly higher at 265 and 255 m elevation which are higher than that at the control elevation of 275 m.All of those indicate that medium and short⁃term flooding can improve the activity of soil microorganisms to a certain extent,while long⁃term flooding environment can greatly inhibit the activity of soil microorganisms.The SMBC in hydro⁃fluctuation belt of Xiaolangdi Reservoir area has a very significant positive correlation with soil moisture content,a significant negative correlation with pH value,and a significant correlation with soil temperature,SOC and total nitrogen.These are considered that their change characteristics can reveal the impact of microbial activities on soil fertility in hydro⁃fluctuation belt of Xiaolangdi Reservoir area.