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Title: Partitioning evapotranspiration using long-term carbon dioxide and water vapor fluxes: New Approach to ET Partitioning

Authors:
ORCiD logo [1]; ORCiD logo [1]
  1. Southwest Watershed Research Center, USDA Agricultural Research Service, Tucson Arizona USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1390369
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 44; Journal Issue: 13; Related Information: CHORUS Timestamp: 2017-09-14 10:33:10; Journal ID: ISSN 0094-8276
Publisher:
Wiley Blackwell (John Wiley & Sons)
Country of Publication:
United States
Language:
English

Citation Formats

Scott, Russell L., and Biederman, Joel A. Partitioning evapotranspiration using long-term carbon dioxide and water vapor fluxes: New Approach to ET Partitioning. United States: N. p., 2017. Web. doi:10.1002/2017GL074324.
Scott, Russell L., & Biederman, Joel A. Partitioning evapotranspiration using long-term carbon dioxide and water vapor fluxes: New Approach to ET Partitioning. United States. doi:10.1002/2017GL074324.
Scott, Russell L., and Biederman, Joel A. 2017. "Partitioning evapotranspiration using long-term carbon dioxide and water vapor fluxes: New Approach to ET Partitioning". United States. doi:10.1002/2017GL074324.
@article{osti_1390369,
title = {Partitioning evapotranspiration using long-term carbon dioxide and water vapor fluxes: New Approach to ET Partitioning},
author = {Scott, Russell L. and Biederman, Joel A.},
abstractNote = {},
doi = {10.1002/2017GL074324},
journal = {Geophysical Research Letters},
number = 13,
volume = 44,
place = {United States},
year = 2017,
month = 7
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on July 12, 2018
Publisher's Accepted Manuscript

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  • Increasing atmospheric carbon dioxide (CO{sub 2}) and nitrous oxide (N{sub 2}O) levels have prompted research on management of the soil C and N pools. The impact of C and N fertilizer addition on N{sub 2}O and CO{sub 2} field emissions in not clear. We determined N{sub 2}O and CO{sub 2} fluxes from a 1-ha bare soil plot using micrometeorological methods with the objective of evaluating the effect of management practices (cultivation, irrigation, fertilizer, and sucrose applications) on the relative importance of both trace gases. Research was conducted at the Elora Research Station (Typic Hapludalf) in Ontario, Canada, over 7 mo.more » The N{sub 2}O concentration gradients were measured using a Tunable Diode Laser Trace Gas Analyzer and the CO{sub 2} gradients using an Infra-Red Gas Analyzer. The transport coefficients were calculated using a Bowen Ratio Energy Balance and two wind profile approaches. These three approaches resulted in similar hourly fluxes. Peak emissions of 250 ng N{sub 2}O m{sup {minus}1} s{sup {minus}1} were measured after wetting of dry soil (WFP < 0.4) through irrigation in 1991, and rain in 1992. Application of ammonium sulfate (100 kg N ha{sup {minus}1}) and irrigation increased N{sub 2}O emissions to 75 ng m{sup {minus}2} s{sup {minus}1}, with a smaller effect caused by two subsequent irrigations on wet soil (WFP >0.6). Carbon dioxide fluxes varied between 0.01 and 0.5 mg m{sup {minus}1} s{sup {minus}1} being the predominant gas contributing to an equivalent CO{sub 2} global-warming potential, but addition of sucrose increased the contribution of N{sub 2} O to twice the contribution of CO{sub 2}. The combined effect of C and N additions (e.g. manure and legume) on the N{sub 2}O emissions in irrigated or high rainfall areas should be considered in the efforts of atmospheric C sequestering. 40 refs., 7 figs., 1 tab.« less
  • Here, recent studies have shown that global Penman-Monteith equation based (PM-based) models poorly simulate water stress when estimating evapotranspiration (ET) in areas having a Mediterranean climate (AMC). In this study, we propose a novel approach using precipitation, vertical root distribution (VRD), and satellite-retrieved vegetation information to simulate water stress in a PM-based model (RS-WBPM) to address this issue. A multilayer water balance module is employed to simulate the soil water stress factor (SWSF) of multiple soil layers at different depths. The water stress factor (WSF) for surface evapotranspiration is determined by VRD information and SWSF in each layer. Additionally, fourmore » older PM-based models (PMOV) are evaluated at 27 flux sites in AMC. Results show that PMOV fails to estimate the magnitude or capture the variation of ET in summer at most sites, whereas RS-WBPM is successful. The daily ET resulting from RS-WBPM incorporating recommended VI (NDVI for shrub and EVI for other biomes) agrees well with observations, with R2 = 0.60 ( RMSE = 18.72 W m-2) for all 27 sites and R2=0.62 ( RMSE 5 18.21 W m-2) for 25 nonagricultural sites. However, combined results from the optimum older PM-based models at specific sites show R2 values of only 0.50 ( RMSE 5 20.74 W m-2) for all 27 sites. RS-WBPM is also found to outperform other ET models that also incorporate a soil water balance module. As all inputs of RS-WBPM are globally available, the results from RS-WBPM are encouraging and imply the potential of its implementation on a regional and global scale.« less
  • Hydrological changes, particularly alterations in water table level, may largely overshadow the more direct effects of global temperature increase upon carbon cycling in arctic and subarctic wetlands. Frozen cores (n=40) of intact soils and vegetation were collected from a bog near Fairbanks, Alaska, and fluxes of CO{sub 2}, CH{sub 4}, and Co in response to water table variation were studied under controlled conditions in the Duke University phytotron. Core microcosms thawed to a 20-cm depth over 30 days under a 20 hour photoperiod with a day/night temperature regime of 20/10{degrees}C. After 30 days the water table in 20 microcosms wasmore » decreased from the soil surface to -15 cm and maintained at the soil surface in 20 control cores. Outward fluxes of CO{sub 2} (9-16 g m{sup -2}d{sup -1}) and CO (3-4 mg m{sup -2}d{sup -1}) were greatest during early thaw and decreased to near zero for both gases before the water table treatment started. Lower water table tripled CO{sub 2} flux to the atmosphere when compared with control cores. Carbon monoxide was emitted at low rates from high water table cores and consumed by low water table cores. Methane fluxes were low (<1 mg m{sup -2}d{sup -1}) in all cores during thaw. High water table cores increased CH{sub 4} flux to 8-9 mg m{sup -2}d{sup -1} over 70 days and remained high relative to the low water table cores (<0.74 mg m{sup -2}d{sup -1}). Although drying of wetland taiga soils may decrease CH{sub 4} emissions to the atmosphere, the associated increase in CO{sub 2} due to aerobic respiration will likely increase the global warming potential of gas emissions from these soils. 43 refs., 4 figs.« less
  • Diffusion of CO{sub 2} across the air-water interface was analyzed with a model that simulates both transport and reaction of CO{sub 2} in a stagnant boundary layer. The atmospheric C influx was determined in relation to several environmental variables: pH, total dissolved inorganic C, temperature, and the thickness of the stagnant boundary layer in relation to ambient windspeed. We used the model to calculate the atmospheric CO{sub 2} influx into experimental ditches for a period of 6 to 8 months, starting in early spring. Three of the six ditches were dominated by aquatic macrophytes and three by benthic algae. Eachmore » series received three levels of external N and P input. A comparison with net C assimilation during the same period, as estimated from continuous oxygen measurements, showed that, especially in the ditches dominated by submersed macrophytes, a sizable fraction of the C requirements during this period could have been obtained from atmospheric CO{sub 2}. In the ditches dominated by benthic algae, this fraction was considerably less, but nonetheless substantial, and was related to the level of N and P loading. Increased primary production due to enhanced external N and P loading increased the atmospheric C input due to the resultant higher pH values. The trophic state with respect to N and P and the availability of C are therefore interrelated. 25 refs., 8 figs., 5 tabs.« less