Influence of soil moisture on the seasonality of nitric oxide emissions from chaparral soils, Sierra Nevada, California, USA

Homyak, Peter M.; Sickman, James O.

doi:10.1016/j.jaridenv.2013.12.008

Cited by 29 publications

(52 citation statements)

References 46 publications

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“…were observed when dry soils were wetted (Homyak and Sickman 2014). Besides these pulses, NO emissions were highest during summer, when soils were dry, and lowest during the wet growing season (<1 ng NO-N m -2 s -1 ) (Homyak and Sickman 2014).…”

Section: Watershed N-budgetmentioning

confidence: 97%

“…Overland flow samples were analyzed for NO 3 -and NH 4 + . Nitric oxide (NO) emissions were measured during WY 2010 in duplicate collars at four different locations representative of the spatial heterogeneity of the catchment (Homyak and Sickman 2014). N 2 O emissions were measured using the static chamber technique (Homyak 2012).…”

Section: Watershed N-budget: Pools and Transformationsmentioning

confidence: 99%

“…Besides these pulses, NO emissions were highest during summer, when soils were dry, and lowest during the wet growing season (<1 ng NO-N m -2 s -1 ) (Homyak and Sickman 2014). Thus, during a dry year, some of the perceived N-retention can be exported via gaseous pathways (Homyak and Sickman 2014).…”

Section: Watershed N-budgetmentioning

confidence: 99%

“…During these dry months, up to 95% of the atmospheric N inputs can be delivered as dry deposition (Bytnerowicz and Fenn 1996;Padgett and others 1999), favoring N accumulation on dry surfaces because of limited diffusion, during a period when chaparral vegetation is senesced and N uptake is low (Mooney and Rundel 1979). The first rain storms of autumn (wet-up), therefore create abrupt pulses of available N when the capacity of plants to use N is low (Mooney and Rundel 1979;Richards 2005, 2006), yielding elevated N losses in gas evasion from soil (Homyak and Sickman 2014) and streamflow (Bernal and others 2005), which are biogeochemical signals of advanced N-saturation (Fenn and others 1996;Meixner and Fenn 2004). Thus, in xeric environments, long periods of N accumulation when N sinks are inactive may complicate indicators of N-saturation.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, we measured atmospheric N inputs, hydrologic N losses, and belowground microbial processes and used a previous study from Chamise Creek for estimating gaseous N export (Li and others 2006;Homyak and Sickman 2014) as well as studies from other chaparral ecosystems in California for estimating N fixation and aboveground N cycling (Kummerow and others 1978;Mooney and Rundel 1979). We also used isotopic techniques (d 15 N and d…”

Section: Introductionmentioning

confidence: 99%

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Assessing Nitrogen-Saturation in a Seasonally Dry Chaparral Watershed: Limitations of Traditional Indicators of N-Saturation

et al. 2014

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To evaluate nitrogen (N) saturation in xeric environments, we measured hydrologic N losses, soil N pools, and microbial processes, and developed an N-budget for a chaparral catchment (Sierra Nevada, California) exposed to atmospheric N inputs of approximately 8.5 kg N ha -1 y -1. Dual-isotopic techniques were used to trace the sources and processes controlling nitrate (NO 3 -) losses. The majority of N inputs occurred as ammonium. At the onset of the wet season (November to April), we observed elevated streamwater NO 3 -concentrations (up to 520 lmol l -1 ), concomitant with the period of highest gaseous N-loss (up to 500 ng N m -2 s -1 ) and suggesting N-saturation. Stream NO 3 -d 15N and d 18O and soil N measurements indicate that nitrification controlled NO 3 -losses and that less than 1% of the loss was of atmospheric origin. During the late wet season, stream NO 3 -concentrations decreased (to <2 lmol l -1 ) as did gaseous N emissions, together suggesting conditions no longer indicative of N-saturation. We propose that chaparral catchments are temporarily N-saturated at £ 8.5 kg N ha -1 y -1 , but that N-saturation may be difficult to reach in ecosystems that inherently leak N, thereby confounding the application of N-saturation indicators and annual N-budgets. We propose that activation of N sinks during the typically rainy winter growing season should be incorporated into the assessment of ecosystem response to N deposition. Specifically, the N-saturation status of chaparral may be better assessed by how rapidly catchments transition from N-loss to N-retention.

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Section: Watershed N-budgetmentioning

confidence: 97%

Section: Watershed N-budget: Pools and Transformationsmentioning

confidence: 99%

Section: Watershed N-budgetmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Assessing Nitrogen-Saturation in a Seasonally Dry Chaparral Watershed: Limitations of Traditional Indicators of N-Saturation

et al. 2014

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Nitrogen trace gas fluxes from a semiarid subtropical savanna under woody legume encroachment

Soper

Boutton

Groffman

et al. 2016

Global Biogeochemical Cycles

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Savanna ecosystems are a major source of nitrogen (N) trace gases that influence air quality and climate. These systems are experiencing widespread encroachment by woody plants, frequently associated with large increases in soil N, with no consensus on implications for trace gas emissions. We investigated the impact of encroachment by N‐fixing tree Prosopis glandulosa on total reactive N gas flux (Nt = NO + N2O + NOy + NH3) from south Texas savanna soils over 2 years. Contrary to expectations, upland Prosopis groves did not have greater Nt fluxes than adjacent unencroached grasslands. However, abiotic conditions (temperature, rainfall, and topography) were strong drivers. Emissions from moist, low‐lying Prosopis playas were up to 3 times higher than from Prosopis uplands. Though NO dominated emissions, NH3 and NOy (non‐NO oxidized N) comprised 12–16% of the total summer N flux (up to 7.9 µg N m−2 h−1). Flux responses to soil wetting were temperature dependent for NO, NH3, and NOy: a 15 mm rainfall event increased flux 3‐fold to 22‐fold after 24 h in summer but had no effect in winter. Repeated soil wetting reduced N flux responses, indicating substrate depletion as a likely control. Rapid (<1 min) increases in NO emissions following wetting of dry soils suggested that abiotic chemodenitrification contributes to pulse emissions. We conclude that temperature and wetting dynamics, rather than encroachment, are primary drivers of N flux from these upland savannas, with implications for future emission patterns under altered precipitation regimes.

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Impacts of chronic N input on the carbon and nitrogen storage of a postfire Mediterranean‐type shrubland

Vourlitis

Hentz

2016

JGR Biogeosciences

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Mediterranean‐type shrublands are subject to periodic fire and high levels of nitrogen (N) deposition, but little is known how chronic N deposition affects carbon (C) and N storage during succession. We conducted a long‐term experiment in Californian chaparral to test the hypothesis that chronic N enrichment would increase postfire C and N accumulation. The experimental layout consisted of a randomized design where four 10 × 10 m plots received 5 g N m−2 annually since 2003 and four 10 × 10 m plots served as controls. Aboveground and belowground C and N pools and fluxes were measured seasonally (every 3 months) for a period of 10 years. Added N rapidly increased soil extractable N pools and decreased soil pH; however, total soil C and N storage were not affected. Added N plots initially had significantly lower C and N storage than control plots, presumably because of nutrient losses from leaching and/or higher belowground C allocation. However, rates of aboveground N and C storage became significantly higher in added N plots after 4–5 years of exposure, thus increasing fuel buildup, which has implications for future fire intensity. This recovering chaparral stand is not yet “N saturated” after 10 years of chronic N input. However, N leaching continues to be higher in added N plots, indicating that postfire chaparral stands in high‐N deposition areas can be important sources of N to groundwater/aquatic systems even if productivity is stimulated by N input.

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Influence of soil moisture on the seasonality of nitric oxide emissions from chaparral soils, Sierra Nevada, California, USA

Cited by 29 publications

References 46 publications

Assessing Nitrogen-Saturation in a Seasonally Dry Chaparral Watershed: Limitations of Traditional Indicators of N-Saturation

Assessing Nitrogen-Saturation in a Seasonally Dry Chaparral Watershed: Limitations of Traditional Indicators of N-Saturation

Nitrogen trace gas fluxes from a semiarid subtropical savanna under woody legume encroachment

Impacts of chronic N input on the carbon and nitrogen storage of a postfire Mediterranean‐type shrubland

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