Stable isotopes of nitrate reveal different nitrogen processing mechanisms in streams across a land use gradient during wet and dry periods
| Autor: | W. W. Wong, J. Pottage, F. Y. Warry, P. Reich, K. L. Roberts, M. R. Grace, P. L. M. Cook |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: | |
| Zdroj: | Biogeosciences, Vol 15, Pp 3953-3965 (2018) |
| Druh dokumentu: | article |
| ISSN: | 1726-4170 1726-4189 |
| DOI: | 10.5194/bg-15-3953-2018 |
| Popis: | Understanding the relationship between land use and the dynamics of nitrate (NO3−) is the key to constrain sources of NO3− export in order to aid effective management of waterways. In this study, isotopic compositions of NO3− (δ15N–NO3− and δ18O–NO3−) were used to elucidate the effects of land use (agriculture in particular) and rainfall on the major sources and sinks of NO3− within the Western Port catchment, Victoria, Australia. This study is one of the very few studies carried out in temperate regions with highly stochastic rainfall patterns, enabling a more comprehensive understanding of the applications of NO3− isotopes in catchment ecosystems with different climatic conditions. Longitudinal samples were collected from five streams with different agriculture land use intensities on five occasions – three during dry periods and two during wet periods. At the catchment scale, we observed significant positive relationships between NO3− concentrations (p δ15N–NO3− (p 3− in our study sites. Artificial fertiliser was the dominant source of NO3− during the wet periods. In addition to artificial fertiliser, nitrified organic matter in sediment was also an apparent source of NO3− to the surface water during the dry periods. Denitrification was prevalent during the wet periods, while uptake of NO3− by plants or algae was only observed during the dry periods in two streams. The outcome of this study suggests that effective reduction of NO3− load to the streams can only be achieved by prioritising management strategies based on different rainfall conditions. |
| Databáze: | Directory of Open Access Journals |
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