Abstract
Non-urban concentrations of nitrogen oxide gases are insufficient to directly impede plant growth processes, but foliar uptake of these gases may represent a significant N source. Measurements of NO{sub 2} and HNO{sub 3} vapor uptake by elements representative of a forest landscape (e.g. foliage, bark, forest floor) were conducted in an open gas exchange system. Under daylight conditions using a mean NO{sub 2} level of 33 ml l{sup {minus}1}, NO{sub 2} uptake by foliage of forest tree species ranged from 0.35 to 5.75 nmol m{sup {minus}2} s{sup {minus}1}. Uptake of NO{sub 2} by broadleaf species was greater than by conifers. Dry bark surfaces showed about half the conductance to NO{sub 2} than did plant shoots. Forest floor samples had a disproportionately high conductance to NO{sub 2} when compared to bark or foliage surfaces. At similar concentrations, uptake of HNO{sub 3} vapor exceeded that for NO{sub 2}. Foliar NO{sub 2} uptake, under stomatal control, was principally to leaf interiors, but HNO{sub 3} uptake occurred to leaf interiors and surfaces. Based on ambient NO{sub 2} concentrations and conductance data scaled to the forest canopy, NO{sub 2} deposition provides from 0.1 to 2.0 kg ha{sup {minus}1} y{sup {minus}1} of nitrogen to natural forestsmore » (0.1 to 3% of annual needs). Conversely, deposition to urban forests may supply >10% of a forest's annual need.« less
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Claims 8
Claim · model-written summary
Forest tree foliage took up nitrogen dioxide at 0.35 to 5.75 nmol m{sup {minus}2} s{sup {minus}1}.
Verbatim
e0“NO{sub 2} uptake by foliage of forest tree species ranged from 0.35 to 5.75 nmol m{sup {minus}2} s{sup {minus}1}”
Claim · model-written summary
Broadleaf species took up more nitrogen dioxide than conifers.
Verbatim
e0“Uptake of NO{sub 2} by broadleaf species was greater than by conifers”
Claim · model-written summary
Bark conductance to nitrogen dioxide was about half that of shoots.
Verbatim
e0“Dry bark surfaces showed about half the conductance to NO{sub 2} than did plant shoots”
Claim · model-written summary
Forest floor conductance to nitrogen dioxide exceeded that of bark or foliage.
- Outcome
- conductance to NO{sub 2}e0
- Direction
- disproportionately highe0
- Comparator
- bark or foliage surfacese0
Not reportedTaxon
Verbatim
e0“Forest floor samples had a disproportionately high conductance to NO{sub 2} when compared to bark or foliage surfaces”
Claim · model-written summary
Nitric acid vapor uptake exceeded nitrogen dioxide uptake at similar concentrations.
Verbatim
e0“At similar concentrations, uptake of HNO{sub 3} vapor exceeded that for NO{sub 2}”
t0“forests”
Claim · model-written summary
Nitrogen dioxide entered leaf interiors, whereas nitric acid entered interiors and surfaces.
Verbatim
e0“Foliar NO{sub 2} uptake, under stomatal control, was principally to leaf interiors, but HNO{sub 3} uptake occurred to leaf interiors and surfaces”
t0“forests”
Claim · model-written summary
Scaled nitrogen dioxide deposition supplied 0.1 to 2.0 kg ha{sup {minus}1} y{sup {minus}1} of nitrogen to natural forests.
Verbatim
e0“NO{sub 2} deposition provides from 0.1 to 2.0 kg ha{sup {minus}1} y{sup {minus}1} of nitrogen to natural forestsmore » (0.1 to 3% of annual needs)”
t0“forests”
Claim · model-written summary
Deposition to urban forests may supply more than 10% of annual nitrogen need.
Verbatim
e0“deposition to urban forests may supply >10% of a forest's annual need”