Ozone fluxes in a Pinus ponderosa ecosystem are dominated by non-stomatal processes: Evidence from long-term continuous measurements

Fares, Silvano; McKay, M.; Holzinger, Rupert; Goldstein, Allen H.

doi:10.1016/j.agrformet.2010.01.007

Cited by 107 publications

(122 citation statements)

References 70 publications

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“…The authors further showed that the remaining non-depositional flux exhibits strong temperature dependence similar to that of monoterpene emissions, leading to the conclusion that incanopy reactions of ozone with unidentified BVOC drive this additional downward flux. Similar behavior has been observed in the longer-term dataset (2001)(2002)(2003)(2004)(2005)(2006) as well (Fares et al, 2010a). Moreover, enhancements in O 3 fluxes coincided with observed increases in BVOC emissions during and after forest thinning in the summer of 2000, while stomatal deposition actually decreased (Goldstein et al, 2004).…”

Section: Introductionsupporting

confidence: 66%

“…Stomatal fluxes, usually calculated independently from observed water vapor fluxes (Monteith and Unsworth, 1990;Thom, 1975), generally account for only 30-70 % of the observed above-canopy ozone flux (Coe et al, 1995;Kurpius and Goldstein, 2003;Goldstein et al, 2004;Hogg et al, 2007;Fares et al, 2010a,b;Altimir et al, 2004Altimir et al, , 2006Rondon et al, 1993). The remaining "non-stomatal" portion of the ozone flux budget has been ascribed to a range of physical and chemical processes, including light-stimulated surface loss (Coe et al, 1995;Rondon et al, 1993), surfacemediated thermal decomposition , aqueous reactions in surface-accumulated liquid water (Altimir et al, 2006), and gas-phase reactions with biogenic volatile organic compounds (BVOC) (Fares et al, 2010a;Goldstein et al, 2004;Hogg et al, 2007;Kurpius and Goldstein, 2003) or nitric oxide (NO) Duyzer et al, 2004) emitted from the ecosystem.…”

Section: Introductionmentioning

confidence: 99%

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Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

et al. 2011

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Abstract. Understanding the fate of ozone within and above forested environments is vital to assessing the anthropogenic impact on ecosystems and air quality at the urbanrural interface. Observed forest-atmosphere exchange of ozone is often much faster than explicable by stomatal uptake alone, suggesting the presence of additional ozone sinks within the canopy. Using the Chemistry of AtmosphereForest Exchange (CAFE) model in conjunction with summer noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007), we explore the viability and implications of the hypothesis that ozonolysis of very reactive but yet unidentified biogenic volatile organic compounds (BVOC) can influence the forest-atmosphere exchange of ozone. Nonstomatal processes typically generate 67 % of the observed ozone flux, but reactions of ozone with measured BVOC, including monoterpenes and sesquiterpenes, can account for only 2 % of this flux during the selected timeframe. By incorporating additional emissions and chemistry of a proxy for very reactive VOC (VRVOC) that undergo rapid ozonolysis, we demonstrate that an in-canopy chemical ozone sink of ∼2 × 10 8 molec cm −3 s −1 can close the ozone flux budget. Even in such a case, the 65 min chemical lifetime of ozone is much longer than the canopy residence time of ∼2 min, highlighting that chemistry can influence reactive trace gas exchange even when it is "slow" relative to vertical mixing. This level of VRVOC ozonolysis could enhance OH and RO 2 production by as much as 1 pptv s −1 and substantially alter their respective vertical profiles depending on the acCorrespondence to: J. A. Thornton (thornton@atmos.washington.edu) tual product yields. Reaction products would also contribute significantly to the oxidized VOC budget and, by extension, secondary organic aerosol mass. Given the potentially significant ramifications of a chemical ozone flux for both incanopy chemistry and estimates of ozone deposition, future efforts should focus on quantifying both ozone reactivity and non-stomatal (e.g. cuticular) deposition within the forest.

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Section: Introductionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

et al. 2011

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“…Similar results/reports on long-term measurement of ozone fluxes at the ecosystem level are rather limited (Zhang et al, 2002;Turnispeed et al, 2009;Fares et al, 2010). Nevertheless, extensive ozone deposition studies over different ecosystems have been performed in order to understand deposition mechanisms and possible harmful effect on ecosystems (e.g., Fowler et al, 2001;Lamaud et al, 2002;Goldstein et al, 2004;Holzinger et al, 2005Holzinger et al, , 2006Altimir et al, 2006;Mészáros et al, 2009;Lamaud et al, 2009;Coyle et al, 2009).…”

Section: Introductionsupporting

confidence: 60%

“…For example, Stella et al (2011) have modelled ozone deposition into crop throughout the growing season by considering soil resistance and humidity dependent cuticular and stomatal resistances with high degree of explanatory power for three measurement sites. In turn Fares et al (2010) observe that non-stomatal deposition into ponderosa pine forest is the dominant process of ozone removal, likely due to the ecosystem's release of VOCs that rapidly react with ozone. Therefore, the control of ozone deposition likely differs between sites and between years and seasons within one site.…”

Section: Introductionmentioning

confidence: 99%

Ozone deposition into a boreal forest over a decade of observations: evaluating deposition partitioning and driving variables

et al. 2012

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Abstract. This study scrutinizes a decade-long series of ozone deposition measurements in a boreal forest in search for the signature and relevance of the different deposition processes. The canopy-level ozone flux measurements were analysed for deposition characteristics and partitioning into stomatal and non-stomatal fractions, with the main focus on growing season day-time data. Ten years of measurements enabled the analysis of ozone deposition variation at different time-scales, including daily to inter-annual variation as well as the dependence on environmental variables and concentration of biogenic volatile organic compounds (BVOCs). Stomatal deposition was estimated by using multi-layer canopy dispersion and optimal stomatal control modelling from simultaneous carbon dioxide and water vapour flux measurements, non-stomatal was inferred as residual. Also, utilising the big-leaf assumption stomatal conductance was inferred from water vapour fluxes for dry canopy conditions. The total ozone deposition was highest during the peak growing season (4 mm s −1 ) and lowest during winter dormancy (1 mm s −1 ). During the course of the growing season the fraction of the non-stomatal deposition of ozone was determined to vary from 26 to 44 % during day time, increasing from the start of the season until the end of the growing season. By using multi-variate analysis it was determined that day-time total ozone deposition was mainly driven by photosynthetic capacity of the canopy, vapour pressure deficit (VPD), photosynthetically active radiation and monoterpene concentration. The multi-variate linear model explained the high portion of ozone deposition variance on daily average level (R 2 = 0.79). The explanatory power of the multivariate model for ozone non-stomatal deposition was much lower (R 2 = 0.38). The set of common environmental variables and terpene concentrations used in multivariate analysis were able to predict the observed average seasonal variation in total and non-stomatal deposition but failed to explain the inter-annual differences, suggesting that some still unknown mechanisms might be involved in determining the inter-annual variability. Model calculation was performed to evaluate the potential sink strength of the chemical reactions of ozone with sesquiterpenes in the canopy air space, which revealed that sesquiterpenes in typical amounts at the site were unlikely to cause significant ozone loss in canopy air space. The results clearly showed the importance of several non-stomatal removal mechanisms. Unknown chemical compounds or processes correlating with monoterpene concentrations, including potentially reactions at the surfaces, contribute to non-stomatal sink term.

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“…As both stomatal movements and surface chemical reactions are affected by environmental factors (e.g., light intensity, temperature) and plant phenology, plant O 3 flux often varies with weather conditions and growth periods (Grulke et al 2007;Fares et al 2010). A single-peak pattern was often observed for both daytime and phenological variations of plant O 3 fluxes, with the maximum values appearing at noon and in the middle of the growing season, respectively (Fares et al 2010;Zhu et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Daytime and Phenological Characteristics of O3 and CO2 Fluxes of Winter Wheat Canopy Under Short-Term O3 Exposure

Tong

Xiao

Qian

et al. 2015

Water Air Soil Pollut

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To analyze the daytime and phenological variations of canopy O 3 and CO 2 uptake of winter wheat, the canopy fluxes of wheat plants were measured using a chamber system with four different O 3 levels (0, 40, 80, and 120 nmol mol −1 ) being applied. During the daytime (7:30-18:00 hours), canopy fluxes usually peaked around noon in early growing stages, while a generally decreasing trend from morning to afternoon was observed in the later stages. O 3 and CO 2 fluxes were positively and negatively correlated with O 3 concentration, respectively. Significant differences were observed in O 3 fluxes but CO 2 fluxes among O 3 treatments. Photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) could affect canopy gas uptake in opposite ways. On the phenological timescale, both O 3 and CO 2 fluxes followed the variation of leaf area index (LAI) with the maximum occurring simultaneously at the booting stage. The daytime mean fluxes varied from −10.6 to −17.2 nmol m −2 s −1 for O 3 and from −5.9 to −19.6 μmol m − 2 s − 1 for CO 2 .Q u a n t i t a t i v e l y i m p o r t a n t O 3 d e p o s i t i o n (−3.1∼−11.6 nmol m −2 s −1) was also observed at night with the ratios being about 40∼70 % relative to the daytime O 3 fluxes for most measuring days, which indicates a significant contribution from non-stomatal components to canopy O 3 removal. This study confirms that environmental variables and plant phenology are important factors in regulating canopy O 3 and CO 2 uptake. O 3 exposure (≤120 nmol mol −1 ) could not significantly affect the CO 2 uptake of wheat canopy in a short time (ca. 10 min).

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Ozone fluxes in a Pinus ponderosa ecosystem are dominated by non-stomatal processes: Evidence from long-term continuous measurements

Cited by 107 publications

References 70 publications

Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

Ozone deposition into a boreal forest over a decade of observations: evaluating deposition partitioning and driving variables

Daytime and Phenological Characteristics of O3 and CO2 Fluxes of Winter Wheat Canopy Under Short-Term O3 Exposure

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