Biogenic hydrocarbon emissions from deciduous and coniferous trees in the United States

Abstract

Measurements of natural hydrocarbon emission fluxes are reported for a northeastern U.S. deciduous forest, for a northwestern U.S. coniferous forest, and for dominant tree species in the Atlanta, Georgia, region. The emission data were obtained by using a vegetation enclosure procedure and a micrometeorological gradient technique. Isoprene fluxes determined by the gradient method in the deciduous forest varied from 2500 #g/m2/h at 20øC to 8000 #g/m2/h at 30øC. Corresponding fluxes obtained with the vegetation enclosure method ranged from 890 to 7300 #g/m2/h. Isoprene fluxes determined by both methods increased exponentially with increasing temperature. Emission rates from isoprene-emitting trees in the Atlanta area were similar to those observed in Pennsylvania. Alpha-pinene fluxes measured in a Douglas fir (Pseudotsuga menziesii) forest ranged from 9 to 1320 #g/me/h. Relative humidity appeared to directly influence the alpha-pinene emission rate. The reasonable agreement between hydrocarbon fluxes obtained with two independent techniques is significant evidence of the general validity of current biogenic hydrocarbon emission rates. levels of approximately 130 ttg/m2/h. In a companion paper, Dement et al. [1975] studied these emissions under varying light, humidity, and temperature conditions. They found that the volatilization rate of monoterpenes is dependent on the vapor pressures of the terpenes, humidity, and the amount of oil present on the surface of the leaf. These investigators also reported that the emission rate is not directly dependent on the photosynthetic activity or on the stomatal opening of the plant. This suggested that the mechanism was physical and that the terpenes were volatilized from the surface of the leaf rather than from the inside. Tingey et al. [1979] used a laboratory gas exchange chamber to study the volatile emissions from live oak (Quercus virginiana) and reported an average emission rate of approximately 30 ttg/g leaf biomass/h. Arnts et al. [1978], in a studysimilar to the gradient profile approach reported in this manuscript, used an energy balance/Bowen ratio technique to estimate the alpha-pinene flux from a plantation of loblolly pine (Pinus taeda). An average flux of 3170 ttg/m2/h was reported, and the authors noted an increase in the emission flux with increasing temperature and water stress and a decrease in flux with increasing wind speed. They also observed substantially lower terpene concentrations in the winter months in ambient samples collected 5 m above the canopy. Using this data base, Knoerr [1980] compared fluxes of alpha-pinene determined from the micrometeorological technique to the results obtained via a branch enclosure method and observed good overall agreement. The most extensive study performed to date on the terpene 2380 570, 1981. Turner, J., Nutrient cycling in a Douglas fir ecosystem with respect to age and nutrient status, Ph.D. thesis, Univ. Wash., Seattle, Wash., 1976. , Assembling a vegetative hydrocarbon emission inventory for the California Sou...

The contribution of reactive carbon emissions from vegetation to the carbon balance of terrestrial ecosystems

“…The recent development of fast response analyzers for a larger range of RCCs has greatly increased capabilities for eddy covariance measurements (e.g., Karl et al, 2001). Peak hourly isoprene fluxes measured in ten North American landscapes, primarily forests, ranged from 7 to 15 mg C m À2 h À1 with peak daily totals of about 0.03-0.1 g C m À2 (Lamb et al, 1985;Guenther et al, 1996a,b;Goldstein et al, 1998;Guenther and Hills, 1998;Westberg et al, 2000). Although none of these studies extended over an entire year, extrapolation of these fluxes using the model of Guenther et al (1995) indicates that annual isoprene emissions at these sites are between 2 and 10 g C m À2 .…”

Isoprene and monoterpene emission rate variability: Model evaluations and sensitivity analyses

“…0148-0227/93/93 JD-00527505.00 temperature also strongly influence seasonal and spatial variations [see Lamb et al, 1987].…”

“…Emissions of biogenic hydrocarbons are estimated to equ•aal or exceed anthropogenic emissions even in industrialized nations such as the United States [Lamb et al, 1987]. Biogenic and anthropogenic hydrocarbons can influence the chemical composition of the atmosphere by controlling the oxidation capacity of the troposphere [Chameides et al, 1988].…”

Are monoterpene emissions influenced by humidity?

“…Monoterpene emissions from coniferous trees can be significant contributors to both photochemical activity and secondary aerosol formation [Chameides et [Janson, 1992;Helmig et al, 1998], fog [Riemer et al, 1994], and dew [Lamb et al 1985; Street et al, 1998]. Some researches have claimed that relative humidity influences monoterpene emissions [e.g.…”