Chai Xue-Si, Lei Li-Guo, Jiang Chang-Sheng, Huang Zhe, Fan Zhi-Wei, Hao Qing-Ju
Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, Chongqing 400716, China.
Huan Jing Ke Xue. 2016 Aug 8;37(8):2979-2988. doi: 10.13277/j.hjkx.2016.08.020.
Taking a typical drawdown area located in Wangjiagou of the Three Gorges Reservoir as the study object, four elevations 180,175,165 and 155 m were selected to explore the effect of water level change on soil microbial biomass carbon (SMBC) and microbial biomass nitrogen (SMBN). Wherein, 175,165 and 155 m elevations located in the fluctuating zone, manifested as short, medium and long-term flooding, respectively; 180 m was used as the control, located on the land and never flooded. Sampling depth in soil samples was 0-20 cm, collected once a week. The results indicated that, soil organic carbon (SOC) and total nitrogen (TN) contents at 180 m had no obvious seasonal changes, while they showed remarkable seasonal trends at 175m, which in spring and summer were significantly higher than in autumn and winter; SMBC and SMBN contents and their allocation ratio at four elevations were similar and had significant seasonal fluctuation, which were highest in autumn and lowest in summer at each elevation, indicating that in drawdown area the microbial activity and turnover rate of soil organic carbon and nitrogen were limited by the high-temperature and low-humidity soil environment in summer. Data analysis showed that, compared with the 180 m elevation, contents of SOC, TN, SMBC and microbial quotient, SMBN and its allocation proportion showed varying degrees of increase, while contents of these indexes were significantly lower than control except SMBN and its allocation proportion, meaning that compared with 180 m short and medium-term flooding was conducive to improve soil carbon, nitrogen and their turnover rate and microbial biomass, however, contents of soil carbon and nitrogen and microbial biomass carbon were significantly restricted at 155 m as soil was subjected to flooding stress, meanwhile the turnover rate of SOC was reduced. Correlation analysis implied that SMBC and SMBN had very significant negative correlation with temperature at 5 cm soil depth and pH, meaning that the two environmental factors had a strong effect on soil microbial biomass.
以三峡水库王家沟典型消落区为研究对象，选取180、175、165和155 m四个高程，探讨水位变化对土壤微生物量碳（SMBC）和微生物量氮（SMBN）的影响。其中，175、165和155 m高程位于消落带，分别表现为短期、中期和长期水淹；180 m作为对照，位于陆地，从未被水淹。土壤样品的采样深度为0 - 20 cm，每周采集一次。结果表明，180 m高程处土壤有机碳（SOC）和全氮（TN）含量无明显季节变化，而175 m高程处呈现显著的季节变化趋势，春季和夏季显著高于秋季和冬季；四个高程处的SMBC和SMBN含量及其分配比例相似，且具有显著的季节波动，各高程均在秋季最高，夏季最低，表明消落区土壤有机碳和氮的微生物活性及周转率受夏季高温低湿土壤环境限制。数据分析表明，与180 m高程相比，SOC、TN、SMBC和微生物商、SMBN及其分配比例的含量均有不同程度增加，但除SMBN及其分配比例外，这些指标的含量均显著低于对照，这意味着与180 m相比，短期和中期水淹有利于提高土壤碳、氮及其周转率和微生物量，然而，155 m高程处土壤碳、氮和微生物量碳含量因土壤遭受水淹胁迫而显著受限，同时SOC周转率降低。相关性分析表明，SMBC和SMBN与5 cm土壤深度处的温度和pH呈极显著负相关，意味着这两个环境因素对土壤微生物量有强烈影响。
