鄱阳湖典型洲滩湿地植被叶片和土壤δ15N特征分析

为研究鄱阳湖典型洲滩湿地植被叶片和土壤δ¹⁵N特征,以蚌湖和修水之间的洲滩作为研究对象,选取典型断面研究2015年10—12月和2016年4月植被叶片和土壤δ¹⁵N的相关关系,探讨土壤含水量和无机氮(铵态氮和硝态氮)对植被叶片和土壤δ¹⁵N的影响。结果表明:大部分C3植被的叶片δ¹⁵N大于C4植被;湿润时期植被叶片和土壤δ¹⁵N大于干旱时期,但湿润时期和干旱时期植被叶片均较土壤富集¹⁵N。铵态氮在湿地土壤中占比高达87.43%,是土壤主要的无机氮,但湿地植被主要吸收硝态氮。研究区氮循环开度较小,土壤δ¹⁵N随着可利用氮素的增加而降低,而随着土壤含水量的增加而增加。植被叶片δ¹⁵N与土壤δ¹⁵N呈显著的正相关关系,植被叶片δ¹⁵N主要受土壤氮素变化和氮同位素分馏的影响。

Characteristics of δ15N of Foliage and Soil at Typical IsletWetland in Poyang Lake

To study the characteristics of δ¹⁵N of foliage and soil at typical islet wetland in Poyang Lake, we took the islet wetland between Benghu Lake and Xiushui River as the research object. We analyzed the relation between foliar δ¹⁵N and soil δ¹⁵N at typical section from October to December, 2015 and in April, 2016. We also examined the influence of moisture content of soil and inorganic nitrogen (ammonium nitrogen and nitrate nitrogen) content on foliar δ¹⁵N and soil δ¹⁵N. Results demonstrated that foliar δ¹⁵N of most C3 plants were larger than that of C4 plants. The foliar δ¹⁵N and soil δ¹⁵N in wet period were larger than those in drought period; however, in both wet and dry periods, the ¹⁵N was more enriched in foliage than in soil. Ammonium nitrogen is the major inorganic nitrogen in the wetland soil, accounting for 87.43%, whereas in wetland plants, nitrate nitrogen was dominantly adsorbed. The opening degree of nitrogen cycle in the study area is small, and the soil δ¹⁵N decreased with the increase of available nitrogen but increased with the rising of soil water content. There is a significant positive correlation between foliar δ¹⁵N and soil δ¹⁵N, and foliar δ¹⁵N is mainly affected by soil’s nitrogen content and nitrogen isotope fractionation.