Nitrous Oxide Emissions from Two Riparian Ecosystems: Key Controlling Variables

Abstract

Abstract. Nitrous oxide (N20 ) emissions were measured weekly to fortnightly between April 2001 and March 2002 from two riparian ecosystems draining different agricultural fields. The fields differed in the nature of the crop grown and the amount of fertiliser applied. Soil water content and soil temperature were very important controls of N20 emission rates, with a 'threshold' response at 24% moisture content (by volume) and 8°e, below which N20 emission was very low. N20 fluxes were higher at the site that had received the most fertiliser N, but N0 3 was not a limiting factor at either site. There was also a ' threshold' effect of rainfall, in which major rainfall events (:::: 10 mm) triggered a pulse of high N20 emission if none of the other environmental factors were limiting. These results suggest the existence of multiple controls on N20 emissions operating at a range of spatial and temporal scales and that non-linear relationships, perhaps with a hierarchical structure, are needed to model these emissions from riparian ecosystems.

Nitrous oxide (N2O) fluxes and their relationships with water‐sediment characteristics in a hyper‐eutrophic shallow lake, China

“…The temporal variation of N 2 O fluxes in our study area was consistent, for example, with temperate climate riparian zones [ Machefert et al , 2004]. High fluxes occurred from June to September, accounting for about 50–60% of the annual emission in our study.…”

“…In our study, the eulittoral zone accounted for about 2–30% of total littoral zone area, while N 2 O fluxes from that area accounted for about 45–78% of the total emissions each month. Highest fluxes in areas with the fluctuating water table were previously observed in the Great Ouse River catchment (U.K.) [ Machefert et al , 2004]. Altering wet/dry condition is an essential physical attribute of this zone that provided optimum conditions for coupled nitrification‐denitrification.…”

Hydrological controls on denitrification in riparian ecosystems

“…These results were compared with those from other studies in the literature. In a previous paper (Machefert et al, 2004), soil moisture was shown to be the main driving control on N 2 O emission from Chicheley, with soil temperature and dissolved organic carbon of secondary importance. Nitrate was rarely if ever limiting in this well-fertilised site.…”

Nitrous oxide fluxes and dissolved N gases (N2 and N2O) within riparian zones along the agriculturally impacted San Joaquin River

“…Large spatial and temporal variability exists in soil denitrification and N 2 O fluxes (e.g., hot spots and hot moments, Groffman et al 2000;Machefert et al 2004;Hunt et al 2007;DeSimone et al 2010). While numerous studies have investigated N 2 O production in the laboratory (e.g., Hunt et al 2007), uncertainties remain in N 2 O fluxes when influenced by the interaction of multiple environmental factors in the field setting.…”