Abstract
Abstract. The key role that biogenic volatile organic compounds (BVOC) play in atmospheric chemistry requires a detailed understanding of how BVOC concentrations will be affected by environmental change. Large-scale screening of BVOC emissions from whole forest ecosystems is difficult with enclosure methods. Leaf composition of BVOC, as a surrogate for direct emissions, can more easily reflect the distribution of BVOC compounds in a forest. In this study, BVOC composition in needles of 92 white pine trees (Pinus strobus), which are becoming a large part of Midwest forests, are tracked for three summers at the University of Michigan Biological Station (UMBS). α-Pinene, the dominant terpene in all samples, accounts for 30–50% of all terpenes on a mole basis. The most abundant sesquiterpenoid was a C15 alcohol identified as germacrene D-4-ol. The relationship between limonene and total other monoterpenes shows two distinct trends in the population of these forests. About 14% (n = 13) of the trees showed high levels of limonene (up to 36% of the total BVOC) in the same trees every year. Assuming that needle concentrations scale with emission rate, we estimate that hydroxyl radical reactivity due to reaction with monoterpenes from white pine increases approximately 6% at UMBS when these elevated concentrations are included. We suggest that chemotypic variation within forests has the potential to affect atmospheric chemistry and that large-scale screening of BVOC can be used to study the importance of BVOC variation.
Highlights
Biogenic volatile organic compounds (BVOC) lead to the formation of tropospheric ozone in the presence of nitrogen oxides (NOx) (Atkinson, 2000) as well as to formation and growth of secondary organic aerosol (SOA) (Andreae, 2009; Laothawornkitkul et al, 2009)
The total global estimated emission rate of BVOC is about 1.2 × 1015 g C per year, while the global anthropogenic VOC emission rate is about 1.0 × 1014 g C per year (Muller, 1992; Guenther et al, 1995)
This study showed that the ratio of limonene and other MT (OMT) did not change throughout the summer and reflected one of the same modes seen at University of Michigan Biological Station (UMBS)
Summary
Biogenic volatile organic compounds (BVOC) lead to the formation of tropospheric ozone in the presence of nitrogen oxides (NOx) (Atkinson, 2000) as well as to formation and growth of secondary organic aerosol (SOA) (Andreae, 2009; Laothawornkitkul et al, 2009). Goldstein et al (2004) showed that forest thinning dramatically enhanced monoterpene (MT) emission and ozone uptake in a California ponderosa pine plantation They suggested that ozone uptake was due to reactions with unmeasured BVOC, with ozone reaction rates fast enough to allow oxidation within the forest canopy. Especially of terpenes, are related to vapor pressure within plant tissues and are greatly influenced by temperature (Guenther et al, 1995; Lerdau et al, 1997). Succession from aspen forests to a higher representation of pines will cause “chemical succession” whereby isoprene gives way to terpenes in the atmosphere. This can lead to a number of atmospheric implications and to issues of forest health. This work reports BVOC levels in white pine needles in Northern Michigan measured over three growing seasons and attempts to estimate the atmospheric influence of chemotypic diversity within this population of white pine
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