外源氮输入对黄河口新生湿地植物-土壤系统硫分布特征的影响

选择黄河口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮(N)输入模拟试验,研究了不同氮输入梯度下(N0,无氮输入;N1,低氮输入,9.0 gN m~(-2)a~(-1);N2,中氮输入,12.0 gN m~(-2)a~(-1);N3,高氮输入,18.0 gN m~(-2)a~(-1))碱蓬湿地植物-土壤系统全硫(TS)分布特征的差异。结果表明,外源N输入明显改变了湿地土壤TS含量的分布状况。随着N输入量的增加,除表层TS含量变化不明显外,其他土层均呈增加趋势。不同氮输入处理下植物各器官的TS含量整体均表现为叶茎根,叶是硫的主要累积器官。尽管氮输入处理并未改变植被的硫分配格局以及其地上与地下之间的硫养分供给关系,但其为适应不同养分环境可进行自身生长特性及养分分配的调整,且这种调整在N2处理下表现的尤为明显。随氮输入量的增加,不同氮处理下植物-土壤系统的S储量整体呈增加趋势,但土壤S储量的增幅远低于植物亚系统S储量的增幅以及N供给的增幅,说明N、S之间的养分供给存在不同步性。研究发现,未来黄河口N养分负荷增加情况下,碱蓬湿地植物-土壤系统的S生物循环速率不但可能会加速,而且N、S养分之间也可能形成一个正反馈机制,并将有利于维持新生湿地的稳定与健康。

Effects of exogenous nitrogen enrichment on the distribution of total sulfur in the plant-soil system of the newly created marshes in the Yellow River estuary, China

The Suaeda salsa marsh in the high tidal flat of the northern Yellow River estuary was selected as the study site, and the total sulfur (TS) in the plant-soil system of S. salsa marsh in the newly created marshes in the Yellow River estuary as affected by different N import treatments (N0, no N import treatment; N1, low N import treatment, 9.0 gN m^-2 yr^-1; N2, middle N import treatment, 12.0 gN m^-2 yr^-1; and N3, high N import treatment, 18.0 gN m^-2 yr^-1) was investigated by conducting in situ experiment of N import. Results showed that the TS contents of in different soil layers significantly changed with N import treatments. Except for the surface soil layer, the other soil layers showed an increasing trend with an increase of N import treatments. The TS contents in different organs of S. salsa under different N import treatments generally followed the order:a leaf > stem > root, indicating that leaves were the key tissues for sulfur (S) accumulation. Although different N import treatments did not alter the patterns of S accumulation in different organs of S. salsa or the nutrient supply relationships between aboveground and belowground tissues, the plant could adjust its growth characteristics and nutrient allocations to adapt different nutrient conditions, and the adaptation was particularly evident in plants in the N2 treatment. S stock in plant-soil system increased with the increase in N import, but the increment of soil S stock was considerably lower than that of plant sub-system N supply, indicating that the nutrient supply between N and S was inconsistent. Our findings revealed that the increase of N loading in the newly created marshes of the Yellow River estuary not only accelerated the S biological cycling rate in the plant-soil system of S. salsa marshes, but also formed a mechanism of positive feedback between N and S, which might favor the maintenance and health of the newly created marshes.