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Decreased N 2 O reduction by low soil pH causes high N 2 O emissions in a riparian ecosystem
Author(s) -
VAN DEN HEUVEL R. N.,
BAKKER S. E.,
JETTEN M. S. M.,
HEFTING M. M.
Publication year - 2011
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/j.1472-4669.2011.00276.x
Subject(s) - denitrification , soil water , nitrous oxide , chemistry , soil ph , nitrogen , environmental chemistry , riparian zone , environmental science , soil science , ecology , organic chemistry , habitat , biology
Quantification of harmful nitrous oxide (N 2 O) emissions from soils is essential for mitigation measures. An important N 2 O producing and reducing process in soils is denitrification, which shows deceased rates at low pH. No clear relationship between N 2 O emissions and soil pH has yet been established because also the relative contribution of N 2 O as the denitrification end product decreases with pH. Our aim was to show the net effect of soil pH on N 2 O production and emission. Therefore, experiments were designed to investigate the effects of pH on NO 3 − reduction, N 2 O production and reduction and N 2 production in incubations with pH values set between 4 and 7. Furthermore, field measurements of soil pH and N 2 O emissions were carried out. In incubations, NO 3 − reduction and N 2 production rates increased with pH and net N 2 O production rate was highest at pH 5. N 2 O reduction to N 2 was halted until NO 3 − was depleted at low pH values, resulting in a built up of N 2 O. As a consequence, N 2 O:N 2 production ratio decreased exponentially with pH. N 2 O reduction appeared therefore more important than N 2 O production in explaining net N 2 O production rates. In the field, a negative exponential relationship for soil pH against N 2 O emissions was observed. Soil pH could therefore be used as a predictive tool for average N 2 O emissions in the studied ecosystem. The occurrence of low pH spots may explain N 2 O emission hotspot occurrence. Future studies should focus on the mechanism behind small scale soil pH variability and the effect of manipulating the pH of soils.