Linking NO and N2O emission pulses with the mobilization of mineral and organic N upon rewetting dry soils

Leitner, Sonja; Homyak, Peter M.; Blankinship, Joseph C.; Eberwein, J. R.; Jenerette, G. Darrel; Zechmeister‐Boltenstern, Sophie; Schimel, Joshua P.

doi:10.1016/j.soilbio.2017.09.005

Cited by 89 publications

(84 citation statements)

References 39 publications

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“…Because diffusion is reduced in dry soil, the products of exoenzymes would accumulate, generating a pool of WEOC that increases with time as the dry season progresses (Steinweg et al 2013, Schaeffer et al 2017. In this way, drying can increasingly concentrate substrates as soils become hydrologically decoupled, generating pools of bioavailable materials that can diffuse to microbes when soils wet up , Homyak et al 2016, Canarini et al 2017, Leitner et al 2017.…”

Section: Introductionmentioning

confidence: 99%

Effects of altered dry season length and plant inputs on soluble soil carbon

Homyak

Blankinship

Slessarev

et al. 2018

Ecology

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Soil moisture controls microbial activity and soil carbon cycling. Because microbial activity decreases as soils dry, decomposition of soil organic matter (SOM) is thought to decrease with increasing drought length. Yet, microbial biomass and a pool of water-extractable organic carbon (WEOC) can increase as soils dry, perhaps implying microbes may continue to break down SOM even if drought stressed. Here, we test the hypothesis that WEOC increases as soils dry because exoenzymes continue to break down litter, while their products accumulate because they cannot diffuse to microbes. To test this hypothesis, we manipulated field plots by cutting off litter inputs and by irrigating and excluding precipitation inputs to extend or shorten the length of the dry season. We expected that the longer the soils would remain dry, the more WEOC would accumulate in the presence of litter, whereas shortening the length of the dry season, or cutting off litter inputs, would reduce WEOC accumulation. Lastly, we incubated grass roots in the laboratory and measured the concentration of reducing sugars and potential hydrolytic enzyme activities, strictly to understand the mechanisms whereby exoenzymes break down litter over the dry season. As expected, extending dry season length increased WEOC concentrations by 30% above the 108 μg C/g measured in untreated plots, whereas keeping soils moist prevented WEOC from accumulating. Contrary to our hypothesis, excluding plant litter inputs actually increased WEOC concentrations by 40% above the 105 μg C/g measured in plots with plants. Reducing sugars did not accumulate in dry senesced roots in our laboratory incubation. Potential rates of reducing sugar production by hydrolytic enzymes ranged from 0.7 to 10 μmol·g ·h and far exceeded the rates of reducing sugar accumulation (~0.001 μmol·g ·h ). Our observations do not support the hypothesis that exoenzymes continue to break down litter to produce WEOC in dry soils. Instead, we develop the argument that physical processes are more likely to govern short-term WEOC dynamics via slaking of microaggregates that stabilize SOM and through WEOC redistribution when soils wet up, as well as through less understood effects of drought on the soil mineral matrix.

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Section: Introductionmentioning

confidence: 99%

Effects of altered dry season length and plant inputs on soluble soil carbon

Homyak

Blankinship

Slessarev

et al. 2018

Ecology

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“…Lastly, Demand et al (2017) found that soil inorganic P (Pi) fluxes measured with microdialysis spanned similar P root uptake rates reported in the literature. Leitner et al (2017a) has shown how diffusive fluxes can be related to greenhouse gas emission (NO, N2O) with quantification of gaseous releases simultaneously with diffusive fluxes after soil drying and rewetting, with high temporal sensitivity. Spatial sensitivity of microdialysis was also exploited by combining the technique with microCT imaging to observe NO3accumulation, and depletion of NH4 + near the roots of maize plants when compared to bulk soil .…”

Section: Relating Diffusive Fluxes To Other Ecologically-relevant Fluxesmentioning

confidence: 99%

“…Initial investigations of soil fluxes employed online setups with a potentiometric detector (for chloride ions) and electrothermal atomic-adsorption spectrometry (for metal ions), and demonstrated the potential for microdialysis to simplify analyses by acting as a clean-up stage to remove humic compounds which can interfere with some online instruments . For the first time in soil, Warren (2018) combined microdialysis with simultaneous mass spectrometry to explore the dynamics of amino acid turnover in soils, allowing for precise measurements of 15 N-13 C L-alanine at one-minute increments, compared to 20+ minutes using conventional fraction collection (Inselsbacher et al, 2011, Leitner et al, 2017a,b, Ganeteg et al, 2017. Detectable concentrations of an added alanine standard decreased to below detection limits within 5 -20 minutes; in contrast to sterilised soils, which still maintained detectable concentrations after three hours, graphically demonstrating the role of microbial consumption in rapid amino acid turnover in soils.…”

Section: Online Analysesmentioning

confidence: 99%

“…Diffusive fluxes have proven a useful measure of soil solute availability, particularly given they are measured in similar units to other relevant fluxes, such as solute uptake by roots (Brackin et al, 2015, Demand et al, 2017 and emissions of greenhouse gases from soil (Leitner et al, 2017b, Leitner et al, 2017a, and are commonly quoted in microdialysis soil studies (Inselsbacher et al, 2011, Shaw et al, 2014, Ganeteg et al, 2017. However, there are some considerations regarding the deployment and interpretation which may influence findings and make comparisons between studies challenging -but these influences could be minimised through standardisation of the technique.…”

Section: Considerations For Measuring Absolute Fluxesmentioning

confidence: 99%

“…There is also some potential for depletions to be misinterpreted -for instance, as uptake by microbes or adsorption to soil particles; although such processes may be difficult to differentiate from sampling depletion. Consideration should be given to the impact of depletion zones when interpreting shortterm time course measurements (minutes to hours), in context of overall dynamics of the soil system, including likely soil concentrations and solute mobility (Leitner et al, 2017a).…”

Section: Considerations For Measuring Absolute Fluxesmentioning

confidence: 99%

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A microdialysis perspective of soil nitrogen availability

Buckley¹

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Soil nitrogen (N) availability is a critical component of ecosystem function and a main driver of below and above ground productivity. As such, the topic is of interest to ecologists exploring the constraints on soil processes as they relate to plant and microbial productivity, as well as agriculturalists seeking to maximise crop N uptake whilst minimising N losses from soil. Soil N encompasses a diversity of compounds spanning from organic to inorganic. Quantifying the bioavailability of different N forms is difficult and likely affected by factors that include climate and water, and the physical, chemical and biological characteristics of soils, all of which can vary significantly at the microsite level.

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Inorganic Nitrogen diffusion in undisturbed volcanic soils during continuous drying–rewetting cycles

Clunes

Deltedesco

Pinochet

et al. 2020

J. Plant Nutr. Soil Sci.

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Background and aim: The diffusion of inorganic nitrogen (N) in soils is strongly affected by their physical characteristics and hydraulic gradients, which enable them to store and transport nutrients over time and space. The objective of this research was to use the microdialysis technique to continuously monitor the diffusive fluxes of inorganic N from the physical N store towards root surfaces in two volcanic soils after soil rewetting.Methods: Undisturbed soil samples were collected in metallic cylinders (230 cm3) at four depths (0–20, 20–40, 40–70, 70–100 cm) in two distinct volcanic soils (Andisol and Ultisol) that are used in agriculture. Diffusive N fluxes were determined during continuous drying and rewetting cycles (0 to 100 kPa) of intact undisturbed soil cores. Soil water content (SWC) at each water potential was calculated.Results and Conclusions: Diffusive fluxes increased significantly (p < 0.001) after rewetting in both soils: 16‐fold in the Andisol, from 32.7 ± 12.1 to 541.5 ± 306.5 nmol N cm−2 h−1 (34 to 62% SWC) and 66‐fold in the Ultisol, from 65.6 ± 25.8 to 4298.7 ± 1289.9 nmol N cm−2 h−1 (31 to 58% SWC) in the upper 20 cm of the soils. In addition, diffusive fluxes decreased with depth in both soils. We found that the residence time of available in these soils strongly depended upon actual SWC and thereby the functionality of the pores in the system. We propose that the ability of the porous system to transport water throughout the soil profile is a relevant parameter within N diffusion, since it allows us to estimate the increase or decrease of diffusive fluxes as a function of the soil water content during continuous drying and rewetting cycles.

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Linking NO and N2O emission pulses with the mobilization of mineral and organic N upon rewetting dry soils

Cited by 89 publications

References 39 publications

Effects of altered dry season length and plant inputs on soluble soil carbon

Effects of altered dry season length and plant inputs on soluble soil carbon

A microdialysis perspective of soil nitrogen availability

Inorganic Nitrogen diffusion in undisturbed volcanic soils during continuous drying–rewetting cycles

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