Abstract: 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.

Key words: islet wetland, plant foliage, δ¹⁵N, nitrogen cycle, nitrogen content, water content in soil, ammonium nitrogen, nitrate nitrogen, Poyang Lake