Preliminary estimates of foliar absorption of 15N-labeled nitric acid vapor (HNO3) by mature eastern white pine (Pinusstrobus)
1990 ◽
Vol 20
(6)
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pp. 857-860
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Keyword(s):
Foliar N
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We used a direct approach to quantify foliar N absorption by exposing foliage of mature eastern white pine (Pinusstrobus L.) to 15N-labeled nitric acid vapor (HNO3). Foliage on terminal portions of branches in a 31-year-old white pine plantation was enclosed in 9.0-L teflon film branch cuvettes and exposed to 10, 50, and 100 ppb H15NO3 for 12–30 h. Foliar absorption rates ranged from 0.026 μg 15N•g−1•h−1 at 10 ppb to 0.267 μg 15N•g−1•h−1 at 100 ppb. Extrapolation to the entire canopy resulted in an estimated absorption of 0.30–0.50 kg N•ha−1•year−1 at ambient HNO3 concentrations. In contrast, canopy input–output estimates for the same forest stand indicated a depletion of 2.3 kg•N•ha−1•year−1 by the forest canopy.