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ENVIRONMENTAL SCIENCE & TECHNOLOGY
AMER CHEMICAL SOC
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Abstract: |
Dissimilatory nitrate reduction to ammonium
(DNRA), the nearly forgotten process in the terrestrial nitrogen
(N) cycle, can conserve N by converting the mobile nitrate into
non-mobile ammonium avoiding nitrate losses via denitrification,
leaching, and runoff. However, global patterns and controlling
factors of soil DNRA are still only rudimentarily known. By a metaanalysis of 231 observations from 85 published studies across
terrestrial ecosystems, we find a global mean DNRA rate of 0.31 ±
0.05 mg N kg−1 day−1, being significantly greater in paddy soils
(1.30 ± 0.59) than in forests (0.24 ± 0.03), grasslands (0.52 ±
0.15), and unfertilized croplands (0.18 ± 0.04). Soil DNRA was
significantly enhanced at higher altitude and lower latitude. Soil
DNRA was positively correlated with precipitation, temperature,
pH, soil total carbon, and soil total N. Precipitation was the main stimulator for soil DNRA. Total carbon and pH were also
important factors, but their effects were ecosystem-specific as total carbon stimulates DNRA in forest soils, whereas pH stimulates
DNRA in unfertilized croplands and paddy soils. Higher temperatures inhibit soil DNRA via decreasing total carbon. Moreover,
nitrous oxide (N2O) emissions were negatively related to soil DNRA. Thus, future changes in climate and land-use may interact with
management practices that alter soil substrate availability and/or soil pH to enhance soil DNRA with positive effects on N
conservation and lower N2O emissions
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