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Long‐term 15N‐nitrogen retention in the vegetated sediments of a New England salt marsh
Author(s) -
White David S.,
Howes Brian L.
Publication year - 1994
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1994.39.8.1878
Subject(s) - salt marsh , environmental science , nitrogen , term (time) , salt lake , marsh , salt (chemistry) , oceanography , hydrology (agriculture) , environmental chemistry , ecology , geology , chemistry , wetland , biology , geomorphology , geotechnical engineering , organic chemistry , physics , quantum mechanics , structural basin
15 N was used in a 7‐yr field study and a laboratory investigation of a single growing season to quantify the amount, timing, and mechanisms of annual N retention and loss in the plant‐sediment system of a short Spartina alterniflora marsh. There was an initial rapid loss of ∼25% of the added 15 NH 4 + through nitrification‐denitrification at a rate of 25.2 mg N m −2 d −1 , with the remaining label being incorporated into plant tissues. Label losses decreased throughout the study as 15 N was increasingly sequestered in the dead organic N pool. About 40% of the injected label remained after seven growing seasons. Total annual N losses were 7.3–7.6 g N m −2 yr −1 based on 15 N losses and estimates of the actively cycling N pool. Export accounted for 26–44% and denitrification for 54–77% of the total N loss. Burial of N in dead belowground organic matter was 3.7–4.1 g N m −2 yr − 1 , similar to estimates determined from accretion and total sediment N data. Recycling of N through translocation from aboveground to belowground biomass and remineralization of dead belowground biomass was the major pathway in the sediment N cycle, equivalent to 67–79% of the annual plant N demand. Annual N losses were balanced by inputs, primarily N 2 fixation. Long‐term N retention appears to be controlled primarily by the competition for DIN between the plants and bacterial nitrifiers‐denitrifiers and secondarily by the relative incorporation of N into aboveground vs. belowground biomass.