Flood pulses control soil nitrogen cycling in a dynamic river floodplain

Shrestha, Juna; Niklaus, Pascal A.; Pasquale, N.; Huber, Benedikt; Barnard, Romain L.; Frossard, Emmanuel; Schleppi, Patrick; Tockner, Klement; Luster, Jörg

doi:10.1016/j.geoderma.2013.09.018

Cited by 52 publications

(44 citation statements)

References 37 publications

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“…In order to improve understanding of how hydromorphological variability relates to ecosystem functioning and services, terrestrial biodiversity as well as ground-and surface Huber et al, 2012;Shrestha et al, 2014) and (F) biodiversity surveys (for exact locations see Fournier et al, 2012b). The picture was taken by BHAteam, Frauenfeld.…”

Section: The Record Project At the Thur River (Switzerland)mentioning

confidence: 99%

“…In both systems, we combined geochemical, biochemical and molecular-biological analysis to identify biogeochemical processes as well as the responsible organisms and to determine process rates and element fluxes (Huber et al, 2012b;Peter et al, 2012a;Samaritani et al, 2011;Shrestha et al, 2012Shrestha et al, , 2014. The results are briefly discussed in Sects.…”

Section: Biogeochemistry: Dynamics Of Organic Carbon Nutrients and Pmentioning

confidence: 99%

“…In a comprehensive study of nitrogen cycling in floodplain soils, we identified two FPZs in the restored section as hot zones of nitrogen turnover and removal : (i) the low-lying alluvial forest with a finetextured soil where anaerobic microsites facilitated coupled nitrification-denitrification; (ii) the gravel bars, characterized by frequent inundation and high sediment deposition rates. Here, major floods led to a strong stimulation of nitrogen mineralization due to temporary input of available organic matter, probably mainly related to the deposition of sandy sediments by the fast over-flowing water (Shrestha et al, 2014). This was followed by enhanced nitrification and denitrification during the drying phase with close coupling of the two processes supported by different redox conditions at the inside and outside of soil aggregates.…”

Section: How Does Morphological Variability Affect Biogeochemical Tramentioning

confidence: 99%

“…Because increased morphological variability in the river bed enhances hyporheic exchange, river restoration may increase the self-cleaning capacity of the river (Lefebvre et al, 2004). The discharge-modulated coupling of groundwater to overlaying soils can then form biogeochemical hotspots and hot moments of carbon and nitrogen turnover (e.g., Peter et al, 2012a, b;Shrestha et al, 2012Shrestha et al, , 2014.…”

Section: Introductionmentioning

confidence: 99%

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Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – the Thur River case study

Schirmer

Luster

Linde

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. River restoration can enhance river dynamics, environmental heterogeneity and biodiversity, but the underlying processes governing the dynamic changes need to be understood to ensure that restoration projects meet their goals, and adverse effects are prevented. In particular, we need to comprehend how hydromorphological variability quantitatively relates to ecosystem functioning and services, biodiversity as well as ground-and surface water quality in restored river corridors. This involves (i) physical processes and structural properties, determining erosion and sedimentation, as well as solute and heat transport behavior in surface water and within the subsurface; (ii) biogeochemical processes and characteristics, including the turnover of nutrients and natural water constituents; and (iii) ecological processes and indicators related to biodiversity and ecological functioning. All these aspects are interlinked, requiring an interdisciplinary investigation approach. Here, we present an overview of the recently completed RECORD (REstored CORridor Dynamics) project in which we combined physical, chemical, and biological observations with modeling at a restored river corridor of the perialpine Thur River in Switzerland. Our results show that river restoration, beyond inducing morphologic changes that reshape the river bed and banks, triggered complex spatial patterns of bank infiltration, and affected habitat type, biotic communities and biogeochemical processes. We adopted an interdisciplinary approach of monitoring the continuing changes due to restoration measures to address the following questions: How stable is the morphological variability established by restoration? Does morphological variability guarantee an improvement in biodiversity? How does morphological variability affect biogeochemical transformations in the river corridor? What are some potential adverse effects of river restoration? How is river restoration influenced by catchment-scale hydraulics and which feedbacks exist on the large scale? Beyond summarizing the major results of individual studies within the project, we show that these overarching questions could only be addressed in an interdisciplinary framework.

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Section: The Record Project At the Thur River (Switzerland)mentioning

confidence: 99%

Section: Biogeochemistry: Dynamics Of Organic Carbon Nutrients and Pmentioning

confidence: 99%

Section: How Does Morphological Variability Affect Biogeochemical Tramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – the Thur River case study

Schirmer

Luster

Linde

et al. 2014

Hydrol. Earth Syst. Sci.

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“…In the framework of an interdisciplinary study in a restored riparian section of the River Thur, Switzerland, pronounced hot spots and moments (McClain et al, 2003) for these biogeochemical processes were identified (Peter et al, 2012a,b). Especially flood events locally intensified OC turnover in the groundwater and impacted N transformation pattern in the riparian soils (Huber et al, 2012;Shrestha et al, 2014). Furthermore, during flood events, significant amounts of air can be delivered to groundwater by the entrapment and dissolution of air bubbles in response to water table fluctuations or groundwater recharge (Mächler et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Flood-Controlled Excess-Air Formation Favors Aerobic Respiration and Limits Denitrification Activity in Riparian Groundwater

Peter

Mächler

Kipfer

et al. 2015

Front. Environ. Sci.

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The saturated riparian zones of rivers act as spatially and temporally variable biogeochemical reactors. This complicates the assessment of biogeochemical transport and transformation processes. During a flood event, excess-air formation, i.e., the inclusion and dissolution of air bubbles into groundwater, can introduce high amounts of dissolved O 2 and thereby affect biogeochemical processes in groundwater. With the help of a field-installed membrane-inlet mass-spectrometer we resolved the effects of flood induced excess-air formation on organic carbon (OC) and nitrogen transformations in groundwater of different riparian zones of a restored section of the River Thur, Switzerland. The results show that the flood event triggered high aerobic respiration activity in the groundwater below a zone densely populated with willow plants. The flood introduced high concentrations of O 2 (230 µmol L −1 ) to the groundwater through the formation of excess air and transported up to ∼400 µmol L −1 OC from the soil/root layer into groundwater during the movement of the water table. A rapid respiration process, quantified via the measurements of O 2 , CO 2 , and noble-gas concentrations, led to fast depletion of the introduced O 2 and OC and to high CO 2 concentration (590 µmol L −1 ) in the groundwater shortly after the flood. The synchronous analysis of different nitrogen species allowed studying the importance of denitrification activity. The results indicate that in the willow zone excess-air formation inhibited denitrification through high O 2 concentration input. Instead, the observed decrease in nitrate concentration (∼50 µmol N L −1 ) may be related to fostered nitrate uptake by plants. In the other riparian zones closer to the river, no significant excess-air formation and corresponding respiration activity was observed. Overall, analyzing the dissolved gases in the groundwater significantly contributed to deciphering biogeochemical processes in the riparian aquifer characterized by pronounced changes in the flow regime and by spatial heterogeneity of the vegetation. Measuring excess-air formation helped identifying and explaining the low denitrification activity in a zone with high OC turnover and to quantify OC sources.

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Environmental drivers of denitrification rates and denitrifying gene abundances in channels and riparian areas

Tomasek

Kozarek

Hondzo

et al. 2017

Water Resources Research

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Intensive agriculture in the Midwestern United States contributes to excess nitrogen in surface water and groundwater, negatively affecting human health and aquatic ecosystems. Complete denitrification removes reactive nitrogen from aquatic environments and releases inert dinitrogen gas. We examined denitrification rates and the abundances of denitrifying genes and total bacteria at three sites in an agricultural watershed and in an experimental stream in Minnesota. Sampling was conducted along transects with a gradient from always inundated (in‐channel), to periodically inundated, to noninundated conditions to determine how denitrification rates and gene abundances varied from channels to riparian areas with different inundation histories. Results indicate a coupling between environmental parameters, gene abundances, and denitrification rates at the in‐channel locations, and limited to no coupling at the periodically inundated and noninundated locations, respectively. Nutrient‐amended potential denitrification rates for the in‐channel locations were significantly correlated (α = 0.05) with five of six measured denitrifying gene abundances, whereas the periodically inundated and noninundated locations were each only significantly correlated with the abundance of one denitrifying gene. These results suggest that DNA‐based analysis of denitrifying gene abundances alone cannot predict functional responses (denitrification potential), especially in studies with varying hydrologic regimes. A scaling analysis was performed to develop a predictive functional relationship relating environmental parameters to denitrification rates for in‐channel locations. This method could be applied to other geographic and climatic regions to predict the occurrence of denitrification hot spots.

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Flood pulses control soil nitrogen cycling in a dynamic river floodplain

Cited by 52 publications

References 37 publications

Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – the Thur River case study

Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – the Thur River case study

Flood-Controlled Excess-Air Formation Favors Aerobic Respiration and Limits Denitrification Activity in Riparian Groundwater

Environmental drivers of denitrification rates and denitrifying gene abundances in channels and riparian areas

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