Nitrogen Speciation Dynamics in Two Contrasting Riparian Ecosystems

H. Prior, Penny J Johnes, M Gibson, J M R Hughes

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)


Research has suggested that riparian ecosystems can significantly reduce the total load of NO3- delivered to surface waters from non-point agricultural sources. Many workers pursue a black box approach to wetland systems and can therefore only speculate as to the mechanisms controlling reductions. A study of N speciation dynamics in two riparian ecosystems of contrasting ecology located on Chalk geology with similar morphological and hydrological characteristics was carried out over a two year period. Site one was a wet woodland supporting a 10 year old stand of alder coppice with mature oak and willow stands. Site two was a water meadow dominated by Carex acutiformis and Glyceria maxima with Apium nodiflorum occupying a drainage channel.

Results indicate nutrient retention is greatest in the water meadow where typically 85 - 90% of total dissolved N flowing into the site is retained within the first 10 m strip adjacent to the arable hillslope during baseflow conditions. This is in contrast to the alder coppice where concentrations of N species within the soil water are higher, and retention capacity lower with, typically, 80% retained within the first 10 m. However, during storm events, concentrations of total dissolved N in soil waters exported from both of the sites increase. At peak flow, concentrations of total dissolved N in waters draining from the wetlands increase up to 10 % and 15 % higher than the water flowing into the water meadow and the alder coppice sites respectively. At both sites, approximately 65 % of the total dissolved fraction is in the form of dissolved organic N, demonstrating the importance of the labile organic N fraction in the export of N to surface waters from non-point sources in the catchment. The results suggest that surface and throughflow hydrological pathways only become important during storm events, when the majority of the total nutrient export to adjacent waters takes place.
Original languageEnglish
Title of host publicationBiogeomon '97
Subtitle of host publicationJournal of Conference Abstracts
PublisherCambridge University Press
Publication statusPublished - 1997


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