Profile distribution characteristics of soil organic nitrogen fractions in the lower reaches of the Heihe River wetland

Abstract

罗如熠,张世熔,徐小逊,李婷.黑河下游湿地土壤有机氮组分剖面的分布特征. 生态学报,2015,35(4) :956鄄 964.Luo R Y, Zhang S R, Xu X X, Li T.Profile distribution characteristics of soil organic nitrogen fractions in the lower reaches of the Heihe River wetland. Acta Ecologica Sinica,2015,35(4) :956鄄 964. 黑河下游湿地土壤有机氮组分剖面的分布特征 罗如熠,张世熔 * ,徐小逊,李摇 婷 1 四川省土壤环境保护重点实验室,成都摇 611130 2 四川农业大学资源环境学院,成都摇 611130 摘要:结合野外调查,用 Bremner 法研究了黑河下游湿地不同土壤类型的有机氮组分,结果表明:在 0-50 cm 土层,5 种土壤有 机氮均以酸解性氮为主,占全氮的 71.04%-81.79%。 泥炭土、沼泽土、草甸土、亚高山草甸土所含的酸解氮、非酸解氮和酸解氮 组分氨态氮、氨基酸态氮、氨基糖态氮含量的剖面分布总体上均随土层深度的增加而呈降低趋势,而风沙土却相反,上述有机氮 组分呈升高趋势。 5 种土壤酸解氮及其组分氨态氮、氨基酸态氮、氨基糖态氮占全氮比例的剖面分布总体上均随土层深度的增 加而呈降低趋势,而非酸解氮却呈升高趋势。 5 种土壤酸解未知态氮含量及占全氮比例均在剖面分布上无明显特征。 在 0-30 cm各相同土层内,5 种土壤酸解氮各组分含量及占全氮比例的大小顺序均为氨基酸态氮>氨态氮>未知态氮>氨基糖态氮;而 在 30-50 cm 土层,5 种土壤酸解氮各组分含量及占全氮比例的大小顺序均无明显特征。 此外,黑河下游湿地土壤干化、沙化过 程中,表层 0-10 cm 土壤有机氮组分含量变化明显,其中土壤氨态氮对生态环境变化最为敏感。Abstract: Nitrogen ( N) is one of the most important element in plant growth and an important part of the global ecosystem substances circulation. Organic N is both the main form of soil N and pool of mineral N. Soil organic N plays an important role in soil fertility, N cycling and environmental protection. Usually, the concentration and distribution of soil organic N mainly affected by soil types, soil level, rhizospheric environment, fertility and farming conditions, etc, and the chemical forms and status of soil organic N is the important factor affecting the availability of soil N. Currently, researchers have focused more on effect of different land use systems on changes of soil organic N fractions, dissolved organic N, particulate organic N and microbial biomass N, as well as effect of different fertilization and irrigation approaches on concentrations and composition of organic N fractions by using the Bremner忆s method to separate soil organic N fractions. Combined with filed investigation, five types of soil samples in the lower reaches of Heihe river wetland were collected, and the organic N fractions were studied using the Bremner忆s method, the results showed that acidolysable N was the dominant fraction of organic N in all the soil samples (0-50 cm soil layer) , and the proportion of acidolysable N to total N was from 71.04% to 81.79%. The concentrations of acidolysable N, non鄄acidolysable N and acidolysable N fractions ( ammonia N, amino acid N, amino sugar N) of Peat soil, Boggy soil, Meadow soil, Subalpine meadow soil decreased, but increased in the Aeolian sandy soil generally with soil depth in the profile. Furthermore, the proportions of acidolysable N and acidolysable N fractions ( ammonia N, amino acid N, amino sugar N) to total N of all the soil samples generally decreased with soil depth2.2.1摇 氨态氮 氨态氮的来源比较复杂,其部分是无机态氮,包括土壤中吸附性铵和固定态铵;部分也可能是来自酸解过 程中某些氨基酸和氨基糖脱氨产生的;还有部分则来自酰胺类化合物,其他来源的相关研究很少 [22] 。 由图 3 可见,5 种土壤氨态氮含量的变化范围为 0郾 11-2.42 g / kg。 在 0-5 cm 土层氨态氮含量差异除泥炭土与沼泽 土、草甸土与亚高山草甸土外,其余土壤类型之间均达显著水平( P<0郾 05) ;在 5-10 cm 土层氨态氮含量差异 除泥炭土与沼泽土外,其余土壤类型之间均达显著水平( P<0郾 05) ;在 10-20 cm 土层氨态氮含量差异除泥炭 土与沼泽土、草甸土与亚高山草甸土、亚高山草甸土与风沙土外,其余土壤类型之间均达显著水平( P<0郾 05) ; 在 20-30 cm 土层氨态氮含量差异除泥炭土与沼泽土,草甸土、亚高山草甸...