Open AccessN 2 O emissions and carbon sequestration in a nitrogen‐fertilized Douglas fir stand
Author(s) -
Jassal Rachhpal S.,
Black T. Andrew,
Chen Baozhang,
Roy Real,
Nesic Zoran,
Spittlehouse D. L.,
Trofymow J. A.
Publication year - 2008
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008jg000764
Subject(s) - fertilizer , greenhouse gas , human fertilization , nitrogen , environmental science , zoology , carbon sequestration , nitrogen fertilizer , soil carbon , urea , atmospheric sciences , soil water , agronomy , chemistry , soil science , physics , ecology , biology , organic chemistry
This study investigated how nitrogen (N) fertilization with 200 kg N ha −1 of a 58‐year‐old West Coast Douglas fir stand influenced its net greenhouse gas (GHG) global warming potential (GWP) in the first year after fertilization. Effects of fertilization on GHG GWP were calculated considering changes in soil N 2 O emissions, measured using the static chamber technique and the soil N 2 O gradient technique; eddy covariance (EC) measured net ecosystem productivity (NEP); and energy requirements of fertilizer production, transport, and its aerial spreading. We found significant N 2 O losses in fertilized plots compared to a small uptake in nonfertilized plots. Chamber‐measured N loss in the fertilized plots was about 16 kg N 2 O ha −1 in the first year, which is equivalent to 10 kg N ha −1 or 5% of the applied fertilizer N. Soil N 2 O emissions measured using the gradient technique, however, exceeded the chamber measurements by about 50%. We also compared a polymer‐coated slow‐release urea with regular urea and found that the former delayed N 2 O emissions but the year‐end total loss was about the same as that from regular urea. Change in NEP due to fertilization was determined by relating annual NEP for the nonfertilized stand to environmental controls using an empirical and a process‐based model. Annual NEP increased by 64%, from 326 g C m −2 , calculated assuming that the stand was not fertilized, to the measured value of 535 g C m −2 with fertilization. At the end of the year, net change in GHG GWP was −2.28 t CO 2 ha −1 compared to what it would have been without fertilization, thereby indicating favorable effect of fertilization even in the first year after fertilization with significant emissions of N 2 O.