Riparian Corridors: A New Conceptual Framework for Assessing Nitrogen Buffering Across Biomes

Pinay, Gilles; Bernal, Susana; Abbott, Benjamin W.; Lupon, Anna; Martı́, Eugènia; Sabater, Francesc; Krause, Stefan

doi:10.3389/fenvs.2018.00047

Cited by 68 publications

(52 citation statements)

References 110 publications

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“…The temporal and spatial balance of connected zones is, in turn, highly dependent on the catchment size, hydrogeologic structure, vegetation, boundary conditions and climatic setting. Geomorphological and ecological processes have been shown to co-create systematic differences in the vertical and lateral distribution of SOC and living plant biomass, with greater concentrations of organic carbon in valley floor than in hillslopes (Piney et al, 2018;Temnerud et al, 2016;Campeau et al, 2019;Thomas et al, 2016). This pattern of SOC distribution may help explain the large variation of stream [DOC] in catchments within similar climate zones but with different hydrological conditions (Moatar et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Temperature controls production but hydrology controls export of dissolved organic carbon at the catchment scale

Wen¹,

Perdrial²,

Bernal³

et al. 2019

Preprint

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Abstract. Lateral carbon flux through river networks is an important and poorly-understood component of the global carbon budget. This work investigates how temperature and hydrology control the production and export of dissolved organic carbon (DOC) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, USA. We applied the catchment-scale hydro-biogeochemical reactive transport model BioRT-Flux-PIHM to simulate the DOC dynamics. We estimated the daily DOC production rate (Rp; the sum of local DOC production rates in individual modeling grid cell) and the daily DOC export rate (Re; the product of concentration and discharge at the stream outlet) to downstream ecosystems. Simulations showed that Rp varied by less than an order of magnitude and primarily hinged on seasonal temperature change. In contrast, Re varied by more than three orders of magnitude with a strong dependence on discharge and hydrological connectivity. During summer, high temperatures led to high atmospheric water demand (and evapotranspiration) that dried and disconnected hillslope to stream. Rp reached its maximum but Re was at its minimum. The stream only exported DOC from the organic-poor groundwater and from soil water in the narrow organic-rich swales with enriched DOC such that DOC accumulated in the catchment. During the wet period (winter and spring), Rp reached its minimum but Re peaked because the stream was re-connected to a greater uphill area, flushing out the stored DOC. The model reproduced the observed concentration discharge (C–Q) relationship characterized by a flushing-dilution pattern with a rise in concentrations to a maximum (flushing) at a threshold discharge and then followed a general dilution with concentrations decreasing with discharge. This pattern was explained by the comparable contribution of organic-poor deeper groundwater and soil water from organic-rich swales at the minimum flow, maximized percentage contribution of soil water from organic-rich swales at the low flow regime, and increased contribution of uphill soil water interflow from uphill with less DOC at the high flow regime. This pattern persisted regardless of DOC production rate as long as the contribution of deeper groundwater flow remained low ( 18 %, the flushing-dilution C–Q pattern shifted towards a flushing-only pattern with DOC concentrations increasing with discharge. This study illustrates the temporal asynchrony of DOC production, mostly controlled by temperature, and DOC export, primarily governed by hydrological flow paths at the catchment scale. The occurrence of warmer and more extreme hydrological events in the future could accentuate this asynchrony, with major lateral export of DOC dominated by a few major storm events whereas DOC is produced and stored in the catchment in the prolonged drought periods.

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Section: Discussionmentioning

confidence: 99%

Temperature controls production but hydrology controls export of dissolved organic carbon at the catchment scale

Wen¹,

Perdrial²,

Bernal³

et al. 2019

Preprint

Self Cite

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“…One potential reason for the rarity of source limitation is that the hydrologic conditions favoring DOC mobilization also stimulate DOC production. Storms or other hydrologic events extend the terrestrialaquatic nexus (Kaiser et al, 2015;Tunaley et al, 2016), reconnecting previously isolated watershed components via aboveground and belowground flow paths, where DOC has accumulated within riparian zones (e.g., Ledesma et al, 2015;Pinay et al, 2018), wetlands (e.g., Cohen et al, 2016;Creed et al, 2003), and hillslope soil and groundwaters (e.g., Oikawa et al, 2014;Pacific et al, 2010;Tunaley et al, 2016). During highflow events, increased hydrologic connectivity and hydraulic head gradients accelerate transport through soils, reducing respiration losses of DOC.…”

Section: Hydrology Regulates Both Transport and Production Of Docmentioning

confidence: 99%

Generality of Hydrologic Transport Limitation of Watershed Organic Carbon Flux Across Ecoregions of the United States

Zarnetske

Bouda

Abbott

et al. 2018

Geophysical Research Letters

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169

173

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Although the flux of dissolved organic carbon (DOC) through freshwaters is nearly equivalent to the net carbon uptake of all terrestrial ecosystems, uncertainty remains about how source processes (carbon production and location) and transport processes (hydrologic connectivity and routing) interact to determine DOC flux across flow conditions and ecoregions. This limits our ability to predict the fluvial carbon flux responses to changes in climate and land use. We used DOC concentration and discharge patterns with ensemble modeling techniques to quantify DOC flux behavior for 1,006 U.S. watersheds spanning diverse climate and land cover conditions. We found that DOC flux was transport‐limited (concentration increased with discharge) in 80% of watersheds and that this flux behavior spanned ecoregions and watershed sizes. The generality of transport limitation demonstrates how coupling discharge models with widely available watershed properties could allow DOC flux to be efficiently integrated into landscape and Earth system models.

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“…We also considered whether the stream in the watershed with the highest level of agricultural activity and urbanization ("El Partido") had higher δ 15 N values and DIN concentrations. We expected this owing to the influence of urban wastewaters, and also due to the highly degraded state of the riparian vegetation, which is likely to reduce the N buffering capacity of the stream in response to diffuse N inputs from agricultural and livestock farming practices (Borja et al, 2009;Pinay et al, 2018). , the marsh (M) and the two catchment areas for the streams included in this study ("La Rocina" (R) and "El Partido" (P)).…”

Section: Introductionmentioning

confidence: 99%

Stable isotopes in helophytes reflect anthropogenic nitrogen pollution in entry streams at the Doñana World Heritage Site

Paredes

Ramírez

Forero

et al. 2019

Ecological Indicators

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A B S T R A C T Nitrogen (N) loading from anthropogenic activities is contributing to the eutrophication and degradation of wetlands worldwide. Doñana (southwestern Spain), includes a dynamic marshland protected as a UNESCO World Heritage Site, which has a catchment area exposed to increasing N inputs from intensive agriculture and poorly treated urban wastewaters. Identifying the sources of N entering this iconic wetland complex is vital for its conservation. To this end, we combined multiyear (2014-2016), spatially-explicit data on N concentration in water samples with measurements on the relative abundance of N stable isotopes (δ 15 N) in Bolboschoenus maritimus and Typha domingensis, two dominant helophytes (i.e. emergent macrophytes) in the Doñana marsh and entry streams. Overall, plant tissues from entry streams showed higher δ 15 N values than those from the marsh, particularly in those streams most affected by urban wastewaters. Isotopic values did not differ between plant species. Water samples affected by isotopically-enriched urban wastewaters and other diffuse organic N inputs (e.g. livestock farming) had relatively high Dissolved Inorganic Nitrogen (DIN) concentrations. In contrast, in streams mainly affected by diffuse N pollution from greenhouse crops, high DIN values were related to isotopically-depleted N sources (e.g., inorganic fertilizers). Thus, helophytes, in combination with other parameters such as N concentration in water or land cover, can be valuable indicators of anthropogenic pressures in Mediterranean wetlands. Helophytes have widespread distributions, and can be readily sampled even when water is no longer present. However, identification of specific N sources through helophyte δ 15 N values is limited when key potential N sources are isotopically undistinguishable (e.g. fertilizers vs. atmospheric sources). cyanobacterial blooms, hypoxia, expansion of floating plants and, ultimately

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Riparian Corridors: A New Conceptual Framework for Assessing Nitrogen Buffering Across Biomes

Cited by 68 publications

References 110 publications

Temperature controls production but hydrology controls export of dissolved organic carbon at the catchment scale

Temperature controls production but hydrology controls export of dissolved organic carbon at the catchment scale

Generality of Hydrologic Transport Limitation of Watershed Organic Carbon Flux Across Ecoregions of the United States

Stable isotopes in helophytes reflect anthropogenic nitrogen pollution in entry streams at the Doñana World Heritage Site

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