JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2016, Vol. 40 ›› Issue (02): 9-15.doi: 10.3969/j.issn.1000-2006.2016.02.002

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The relative importance of dissimilatory nitrate reduction to ammonium and denitrification in sediments in a typical coastal wetland

XU Sha, CHEN Yuan, YIN Jie, HAN Jiangang*, XUE Jianhui   

  1. Co-Innovation Center for the Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing 210037, China
  • Online:2016-04-18 Published:2016-04-18

Abstract: This study aims to investigate nitrate reduction in sediments in a typical coastal wetland. Sediment samples were taken in different season and in different vegetation conditions(Phragmites australis, Spartina alterniflora community, the intergrowth area of the two species and mudflat)in Chongming Dongtan wetland in the Yangtze River Delta of China. Rates of dissimilatory nitrate reduction to ammonium(DNRA)and denitrification(Den)were estimated using 15N isotope dilution technique to detect the relative importance of the two reduction processes. Results showed that: ① Den rates in Spartina alterniflora community arrived to 31.29 μg/(kg·h)in winter, which was the highest among four vegetation communities(P<0.05). In contrast, this rates decreased to a very low range of 2.35-3.36 μg/(kg·h)in other three seasons. It revealed that there was a potential high amount of N loss via Den in winter in Spartina alterniflora community. ② DNRA rates in the mudflat(>120 μg/(kg·h))were much higher than those observed in vegetation community(<80 μg/(kg·h))in spring and winter. For different vegetations, the rate in Spartina alterniflora community was the highest(P<0.05). In contrast, DNRA rates in sediments without vegetation were lower than those with vegetation in summer and autumn, and no significant difference among three communities was found. This suggested that Spartina alterniflora possibly facilitates DNRA in spring and winter. ③ The ratios of DNRA and Den in Spartina alterniflora community(17-29)were much higher than those in the other vegetations(1-14)in spring, summer and autumn. However, in winter, this ratios were lower than the others(P<0.05). Therefore, DNRA dominates the reduction of nitrate in the coastal wetland. It would be very necessary to control of eutrification and N2O emission to reduce Spartina alterniflora in a coastal wetland. It is effective to control eutripication and to reduce N2O emission via reducing S. alterniflora in coastal metlands.

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