水沙条件及氮输入对黄河口滨岸潮滩湿地碱蓬和土壤15N吸收特征的影响

受自然及人为活动的影响，黄河三角洲水沙条件存在较大变化，由此带来的外源营养物质增加对潮滩湿地植被生长及元素吸收利用具有重要的影响。为此采用3因素4水平的正交试验，以黄河口滨岸潮滩湿地先锋物种碱蓬（Suaeda salsa）为研究对象，利用¹⁵N示踪技术，研究了水沙条件及氮输入对碱蓬和土壤¹⁵N吸收特征的影响。结果表明：淹水深度、泥沙沉积及氮输入对土壤全氮含量的影响不显著，但外源氮输入对土壤¹⁵N固持量（N_dff）和比例（N_dff%）的影响达到显著水平，且最大值（10.44 mg/kg和3.83%）均出现在W₄S₂N₃（30 cm淹水+3 cm泥沙沉积+6 g/m²氮输入）处理；碱蓬叶和茎中全氮含量、¹⁵N吸收量（N_dff）及比例（N_dff%）在深淹水和泥沙沉积处理时较大，而根中全氮含量、N_dff及N_dff%在高氮输入较大。且根N_dff和N_dff%最大值（1.10 mg/kg和18.21%）在W₁S₄N₄（2 cm淹水+12 cm泥沙沉积+9 g/m²氮输入）处理时取得，此时碱蓬的生长情况最好，表明适当的淹水和泥沙埋深以及高氮输入（9 g/m²）有利于根系对外源氮的吸收，从而促进植株的生长。由此可见，在黄河三角洲水沙变化大的背景下，淹水、泥沙沉积和外源氮输入的适当把控，可促进碱蓬对外源氮的吸收利用而有助于其生长，从而对维护黄河三角洲潮滩湿地的健康具有重要作用。

15N absorption characteristics for Suaeda salsa and sediment under different water-sediment conditions and nitrogen input in the Yellow River delta

Water and sediment condition changed greatly due to natural conditions and human activities, which brought sediment and exogenous substances input influenced on the vegetation growth and element absorption in the tidal flat wetland in the Yellow River delta. Orthogonal test with three factors and four levels were established, and we selected Suaeda salsa as study object to examine the ¹⁵N absorption characteristics for S. salsa and sediment under different water-sediment conditions and nitrogen input using ¹⁵N tracer technique. The results showed that the influence of water depth, sediment burial depth and nitrogen input on sediment total nitrogen content did not reach significant level, while nitrogen input had significant influence on sediment ¹⁵N derived from fertilizer (N_dff) and proportion (N_dff%), and the maximum values (10.44 mg/kg and 3.83%) were observed at W₄S₂N₃ (30 cm water depth+3 cm sediment burial+6 g/m² nitrogen input) treatment. Stem and leaf total nitrogen content, N_dff% and N_dff reached maximum value at higher water depth and sediment burial level, while root total nitrogen content, N_dff% and N_dff were higher at high nitrogen input level. The maximum values of root N_dff% (18.21%) and N_dff (1.10 mg/kg) were observed at W₁S₄N₄ (2 cm water depth+12 cm sediment burial +9 g/m² nitrogen input) treatment, and the growth of S. salsa was best at this treatment. So we concluded that proper control of water depth, sediment burial, and high nitrogen input (9 g/m²) was conducive to nitrogen absorption by roots, and then promoting the S.sasla growth. Consequently, the control of water depth, sediment burial and nitrogen input plays an important role in maintaining the health of tidal flat wetland under the background of large variation of water and sediment condition in the Yellow River delta.