Hajati, Mithra, White, Shawn, Moosdorf, Nils and Santos, Isaac R. (2020) Modeling Catchment-Scale Nitrogen Losses Across a Land-Use Gradient in the Subtropics. Frontiers in Earth Science, 8 . DOI https://doi.org/10.3389/feart.2020.00347.

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Abstract

Changing land use in subtropical and tropical catchments to farmland can result in higher nitrogen (N) loss to aquatic ecosystems. Here, we developed a lumped water and N balance model to estimate regional N losses to creeks at catchment scale within understudied subtropical catchments in Australia. The conceptual water balance model CoCa-RFSGD was extended by the nitrogen mass balance in top and subsoil by adding nitrogen cycle transformation estimates depending on meteorological, soil, and land-use properties. The model estimates the impact of pristine and agricultural land use on catchment-wide water quality using only low-order creek samples as water quality measurements of nitrate and nitrite (NOx) with increased model performance with increased agricultural coverage. The model revealed that an agricultural proportion of 3% in the study site drove a 3.5-fold increase of N losses to creeks and a 6.7-fold increase of N losses to the atmosphere compared to catchments without agriculture. Agricultural land use lost 92 kg-N ha−1, 85% of which evaded to the atmosphere and 15% was discharged via surface waters. A change from forest to cleared land may increase the total denitrification potential of a catchment. Overall, our lumped model provides a simple but effective tool to upscale local aquatic water quality measurements to the catchment scale, allowing for assessment of changing land use on aquatic N loads in areas with limited data availability.

Document Type: Article
Programme Area (enter as: PA1/PA2/PA3/PA4/PA5): PA3
Research affiliation: Biogeochemistry and Geology > Submarine Groundwater Discharge
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: https://doi.org/10.3389/feart.2020.00347
ISSN: 2296-6463
Date Deposited: 11 Dec 2020 11:20
Last Modified: 11 Dec 2020 11:29
URI: http://cris.leibniz-zmt.de/id/eprint/4462

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