Precipitation legacies amplify ecosystem nitrogen losses from nitric oxide emissions in a Pinyon–Juniper dryland

Krichels, Alexander H.; Greene, Aral C.; Jenerette, G. Darrel; Spasojevic, Marko J.; Glassman, Sydney I.; Homyak, Peter M.

doi:10.1002/ecy.3930

Cited by 7 publications

(7 citation statements)

References 29 publications

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“…For example, even with similar amount of precipitation in simulation years 26 and 40, N export was much higher in year 40 due to the legacy of a multi‐year drought (Figures 7c and 7e). Recent research has similarly shown that precipitation variability can have positive or negative legacy effects on dryland productivity, which can in turn influence N cycling and export (Gherardi & Sala, 2015; Krichels et al., 2022). However, the direction of N responses can vary along long‐term precipitation gradients.…”

Section: Discussionmentioning

confidence: 99%

Simulating the Role of Biogeochemical Hotspots in Driving Nitrogen Export From Dryland Watersheds

Ren,

Hanan,

Greene

et al. 2024

Water Resources Research

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Climate change and nitrogen (N) pollution are altering biogeochemical and ecohydrological processes in dryland watersheds, increasing N export, and threatening water quality. While simulation models are useful for projecting how N export will change in the future, most models ignore biogeochemical “hotspots” that develop in drylands as moist microsites in the soil become hydrologically disconnected from plant roots when soils dry out. These hotspots enable N to accumulate over dry periods and rapidly flush to streams when soils wet up. To better project future N export, we developed a framework for representing hotspots using the ecohydrological model RHESSys. We then conducted a series of virtual experiments to understand how uncertainties in model structure and parameters influence N export to streams. Modeled N export was sensitive to three major factors (a) the abundance of hotspots in a watershed: N export increased linearly and then reached an asymptote with increasing hotspot abundance; this occurred because carbon and N inputs eventually became limiting as hotspots displaced vegetation cover, (b) the soil moisture threshold required for subsurface flow from hotspots to reestablish: peak streamflow N export increased and then decreased with an increasing threshold due to tradeoffs between N accumulation and export that occur with increasingly disconnected hotspots, and (c) the rate at which water diffused out of hotspots as soils dried down: N export was generally higher when the rate was slow because more N could accumulate in hotspots over dry periods, and then be flushed more rapidly to streams at the onset of rain. In a case study, we found that when hotspots were modeled explicitly, peak streamflow nitrate export increased by 29%, enabling us to better capture the timing and magnitude of N losses observed in the field. N export further increased in response to interannual precipitation variability, particularly when multiple dry years were followed by a wet year. This modeling framework can improve projections of N export in watersheds where hotspots play an increasingly important role in water quality.

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Section: Discussionmentioning

confidence: 99%

Simulating the Role of Biogeochemical Hotspots in Driving Nitrogen Export From Dryland Watersheds

Ren,

Hanan,

Greene

et al. 2024

Water Resources Research

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“…Over the last century, atmospheric N deposition and climate change have increased both greenhouse gas emissions (e.g., NO and N 2 O) and stream nitrate export from many dryland watersheds in western North America (Groffman, 2012; Homyak et al., 2016; Krichels et al., 2022). Because these gaseous and hydrologic N fluxes can exacerbate global climate change, decrease aquatic biodiversity, and harm human health (Galloway et al., 2003; Gustine et al., 2022; Meyer et al., 2022), it is important to be able to predict how they will change in the future.…”

Section: Discussionmentioning

confidence: 99%

“…These findings suggest that prolonged drought followed by larger, more intense storms can have the strongest effect on streamflow nitrate. This occurs because multi‐year droughts that occur with greater intermittency can reduce N uptake by plants and enable N to accumulate in soils (Krichels et al., 2022; Winter et al., 2023). Subsequent storms then flush accumulated nitrate to streams before plants can take it up.…”

Section: Discussionmentioning

confidence: 99%

“…Precipitation plays an important role in driving N cycling, uptake, and export (Homyak et al., 2017; Schimel, 2018). However, in drylands, these processes can act on different timescales and high precipitation variability can complicate our ability to predict the fate of atmospherically deposited N (Homyak et al., 2014; Howarth et al., 2006; Krichels et al., 2022; Ren et al., 2024a).…”

Section: Introductionmentioning

confidence: 99%

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Dryland Watersheds in Flux: How Nitrogen Deposition and Changing Precipitation Regimes Shape Nitrogen Export

Ren,

Hanan,

D'Odorico

et al. 2024

Earth's Future

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Atmospheric nitrogen (N) deposition and climate change are transforming the way N moves through dryland watersheds. For example, N deposition is increasing N export to streams, which may be exacerbated by changes in the magnitude, timing, and intensity of precipitation (i.e., the precipitation regime). While deposition can control the amount of N entering a watershed, the precipitation regime influences rates of internal cycling; when and where soil N, plant roots, and microbes are hydrologically coupled via diffusion; how quickly plants and microbes assimilate N; and rates of denitrification, runoff, and leaching. We used the ecohydrological model RHESSys to investigate (a) how N dynamics differ between N‐limited and N‐saturated conditions in a dryland watershed, and (b) how total precipitation and its intra‐annual intermittency (i.e., the time between storms in a year), interannual intermittency (i.e., the duration of dry months across multiple years), and interannual variability (i.e., variance in the amount of precipitation among years) modify N dynamics and export. Streamflow nitrate (NO3−) export was more sensitive to increasing rainfall intermittency (both intra‐annual and interannual) and variability in N‐limited than in N‐saturated model scenarios, particularly when total precipitation was lower—the opposite was true for denitrification which is more sensitive in N‐saturated than N‐limited scenarios. N export and denitrification increased or decreased more with increasing interannual intermittency than with other changes in precipitation amount. This suggests that under future climate change, prolonged droughts that are followed by more intense storms may pose a major threat to water quality in dryland watersheds.

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“…The results of soil nitrate content assessment would be considered inconsistent considering that soil nitrate concentration can vary substantially in a short time periods, because of rainfall events and microbial activity (Krichels et al., 2020). In this study, it was compared the soil nitrate content between season and treatment because of the dry summers in our study area, characterized by high temperatures and a lack of rainfall for 3 months.…”

Section: Discussionmentioning

confidence: 99%

A single nitrogen application maintains wheat yield and quality in dryland Mediterranean Vertisol

Fernandez‐Garcia,

Lopez‐Bellido,

Lopez‐Bellido

et al. 2023

Soil Use and Management

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PurposeIn dryland Mediterranean Vertisols, split nitrogen (N) application is usual in wheat crops. Due to the high clay content of these soils and the low rainfall, a single application might offer ecological and economic benefits without yield loss.MethodsWe conducted a five‐year study as part of a long‐term experiment and compared the split application of N (50 % at tillering, 50 % at stem elongation phase) with a single application (tillering) in 10 cropping systems resulting from the combination of type of cultivation (no‐till and conventional tillage) and two‐year crop rotations (wheat‐wheat, wheat‐fallow, wheat‐chickpea, wheat‐faba bean and wheat‐sunflower).Resultsdepending on the system × crop rotation interaction, a single application of 100 or 150 kg N ha ‐1 maintained grain yield, protein content and apparent N recovery, with no effect on nitrate content compared with a traditional split application. The average grain yield did not differ between split and single application of N (3.27 and 3.23 Mg ha‐1 respectively for single and split application of 100 kg N ha‐1 rate; 3.46 and 3.40 Mg ha‐1 respectively for single and split application of 150 kg N ha‐1 rate). The soil nitrate concentration at pre‐seeding in the 0–0.3 m layer showed similar results, except in the case of the wheat‐faba rotation, with lower nitrate concentration in the sub‐subplots of single application and no‐till.ConclusionsThis work shows that adopting the single N application strategy in rotations on Mediterranean dryland Vertisols will reduce economic and environmental costs.

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Precipitation legacies amplify ecosystem nitrogen losses from nitric oxide emissions in a Pinyon–Juniper dryland

Cited by 7 publications

References 29 publications

Simulating the Role of Biogeochemical Hotspots in Driving Nitrogen Export From Dryland Watersheds

Simulating the Role of Biogeochemical Hotspots in Driving Nitrogen Export From Dryland Watersheds

Dryland Watersheds in Flux: How Nitrogen Deposition and Changing Precipitation Regimes Shape Nitrogen Export

A single nitrogen application maintains wheat yield and quality in dryland Mediterranean Vertisol

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