Distribution characteristics of organic matter and total nitrogen in the soils of water-levelfluctuating zone of Three Gorges Reservoir area

Abstract

在三峡库区消落带落干期间(2010年4月),对库区巫山-重庆主城区段消落带土壤有机质(OM)和全氮(TN)含量分布及与土壤理化性质的相关性进行了调查研究.结果表明该区域消落带土壤OM和TN含量均较低,分别为10.70±4.03和0.84±0.39 mg/g,且服从正态分布.消落带土壤碳氮比(C/N)较低,推测消落带土壤无机氮在淹水期间存在向上覆水体释放的可能性.在与其它关于土壤OM和TN含量研究的比较中,研究区域内土壤OM和TN含量处于偏低的水平;而在与对照带样品的比较分析中发现,消落带样品的OM和TN含量变异系数均偏低,因此消落带干湿交替可减小不同区域消落带之间土壤OM和TN含量差异.相关性分析表明,消落带土壤pH、ORP、TN与OM之间呈显著正相关,可见研究范围内消落带土壤氮形态可能主要以有机氮的形式存在于有机质中,而C/N与TN呈负相关,与OM相关性不显著,表明C/N的大小主要取决于TN含量.;The distribution characteristics of organic matter(OM) and total nitrogen(TN) in the soils of water-level-fluctuating zone(WLFZ) of Three Gorges Reservoir were studied during the non-flooded period, while the correlation among the soil physicalchemical characteristics, OM and TN contents was also be analyzed. OM and TN contents in the soils of WLFZ were both fairly low, were 10.70 ± 4.03 and 0.84 ± 0.39 mg/g, respectively; however, they followed the normal distribution. The lower C/N ratio of the soils of WLFZ suggested possibility of releasing of inorganic nitrogen from soil in the WLFZ to overlying water in the flood period. Compared with other study areas, the OM and TN contents were at the low level. The variation coefficients of OM and TN contents of the soil samples of WLFZ were on the low side by comparison with those in control zone. That is why the differences of OM and TN contents among difference WLFZ of study areas could be reduced by cyclic drying and wetting of WLFZ periodically. Correlation analysis showed that pH, oxidation-reduction potential(ORP), TN was significantly and positively correlated with OM. The result indicated that organic nitrogen was the main nitrogen compositions in soils of WLFZ of the study area. Soil C/N ratio was negatively correlated with TN, but insignificantly correlated with OM, suggesting that soil C/N ratio was mainly determined by the content of TN.