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 investigatedby 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.