贵州草海湿地不同植物群落表层土壤氮素的赋存特征

在湿地生态系统氮循环过程中，湿地土壤养分供给状况及可利用水平与氮素含量存在直接关系。本研究以贵州草海湿地自然演替下植物群落表层土壤氮素含量作为研究对象，探讨四种典型湿地植物群落（牛筋草、李氏禾、香薷和芦苇）土壤中硝态氮、铵态氮、速效氮和全氮含量以及不同土壤团聚体粒径下湿地土壤氮素的空间分布特征。结果表明：（1）各植物群落土壤阳离子交换量与全氮含量分布趋势基本一致，其中芦苇群落土壤中阳离子交换量、速效氮和全氮含量最高；（2）各植物群落不同粒径土壤团聚体AN和TN含量均无显著差异（p>0.05）；芦苇群落土壤硝态氮含量在各粒径土壤团聚体中含量均低于其他植物群落；李氏禾群落土壤氨态氮含量在不同粒径土壤团聚体中存在显著差异（p<0.05）。植物群落表层土壤氮素含量分布受植物种类及自身凋落物、降雨量和地势、微生物活动和有机质等因素的影响，土壤硝化作用受到抑制或促进，各植物群落铵态氮和硝态氮含量分布有显著差异（p<0.05）。

Characteristics of surface soil nitrogen occurrence of different plant communities in Caohai Wetland, Guizhou

In the process of nitrogen cycling in wetland ecosystem, there is a direct relationship between the supply and availability of wetland soil nutrients and nitrogen content. In this study, the nitrogen content which existing in the surface soil of the plant community under the natural succession of the Caohai Wetland in Guizhou Province was selected as the research object. The content of nitrate nitrogen(NO3--N), ammonium nitrogen(NH4+-N), available nitrogen (AN) and total nitrogen (TN) in four kinds of phytocoenosium as well as the spatial distribution characteristics of wetland soil nitrogen under different soil aggregate particle sizes were studied. The surface soil of four typical wetland plant communities (i.e. Goosegrass, Leesgrass, Elsholtzia and Phragmites) were collected, and the physical and chemical properties of each layer of the soil were measured. The results showed that: (1) The distribution trend of soil cation exchange capacity (CEC) and TN content in each plant community was basically the same. The contents of CEC, AN and TN in the soil of Phragmites communis were the highest, which were 362.96±61.48 mg kg-1, 22.17±2.02 mg kg-1 and 0.35±0.18 g kg-1, respectively; (2) The contents of AN and TN in soil aggregates with different particle sizes in each plant community had no significant difference (p>0.05). In the Phragmites community, the contents of NO3--N in the soil aggregates with different size were the lowest; in the Leesgrass community, the contents of NH4+-N in the soil aggregates with different sizes were significantly different (p<0.05). In August, plants were in the vigorous growth period, while Caohai was in the wet period. The distribution of nitrogen contents in the surface of the plant community was affected by plant species, its own litter, rainfall, topography, microbial activities, organic matter, and growth period et al. factors. As a result, soil nitrification was inhibited or promoted, and the final manifestation was that the distribution of ammonium nitrogen and nitrate nitrogen in each plant community was significantly different. The nitrogen content of wetland surface soil was also affected by the external nitrogen input in the water body and the distribution structure of nitrogen itself in the natural soil. Therefore, the nitrogen content of various plant communities was not consistent, especially the content of TN in the soil.