US EPA

1566842 

Journal Article 

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in a temperate re-connected floodplain 

Sgouridis, F; Heppell, CM; Wharton, G; Lansdown, K; Trimmer, M 

2011 

1 

Water Research
ISSN: 0043-1354
EISSN: 1879-2448 

45 

16 

4909-4922 

English 

21813153 

10.1016/j.watres.2011.06.037 

WOS:000295386800021 

The relative magnitudes of, and factors controlling,
denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in the soil
of a re-connected temperate floodplain divided into four different land management zones (grazing
grassland, hay meadow, fritillary meadow and a buffer zone). Soil samples were collected from
each zone to measure their respective potentials for nitrate attenuation using (15)N both at the
surface and at depth in the soil column and additional samples were collected to measure the
lability of the organic carbon. Denitrification capacity ranged between 0.4 and 4.2 (mu mol N g
(-1) dry soil d(-1)) across the floodplain topsoil and DNRA capacity was an order of magnitude
lower (0.01-0.71 mu mol N g(-1) d(-1)). Land management practice had a significant effect on
denitrification but no significant effects were apparent for DNRA. In this nitrogen-rich
landscape, spatial heterogeneity in denitrification was explained by differences in lability and
the magnitude of organic carbon associated with different management practices (mowing and
grazing). The lability of organic carbon was significantly higher in grazing grassland in
comparison to other ungrazed areas of the floodplain, and consequently denitrification capacity
was also highest in this area. Our results indicate that bacteria capable of DNRA do survive in
frequently flooded riparian zones, and to a limited extent, compete with denitrification for
nitrate, acting to retain and recycle nitrogen in the floodplain. Exponential declines in both
denitrification and DNRA capacity with depth in the floodplain soils of a hay meadow and buffer
zone were controlled primarily by the organic carbon content of the soils. Furthermore, grazing
could be employed in re-connected, temperate floodplains to enhance the potential for nitrate
removal from floodwaters via denitrification. (C) 2011 Elsevier Ltd. All rights reserved. 

Denitrification; DNRA; Floodplain; Lability; Land use management; River restoration