Chemodiversity of a Scots pine stand and implications for terpene air concentrations

[摘要] Atmospheric chemistry in background areas is strongly influenced by naturalvegetation. Coniferous forests are known to produce large quantities ofvolatile vapors, especially terpenes. These compounds are reactive in theatmosphere, and contribute to the formation and growth of atmospheric newparticles.Our aim was to analyze the variability of mono- and sesquiterpene emissionsbetween Scots pine trees, in order to clarify the potential errors caused byusing emission data obtained from only a few trees in atmospheric chemistrymodels. We also aimed at testing if stand history and seed origin has aninfluence on the chemotypic diversity. The inherited, chemotypic variabilityin mono- and sesquiterpene emission was studied in a seemingly homogeneous48 yr-old stand in Southern Finland, where two areas differing in theirstand regeneration history could be distinguished. Sampling was conducted inAugust 2009. Terpene concentrations in the air had been measured at the samesite for seven years prior to branch sampling for chemotypes.Two main compounds, α-pinene and Δ³-carene formedtogether 40–97% of the monoterpene proportions in both the branchemissions and in the air concentrations. The data showed a bimodaldistribution in emission composition, in particular in Δ³-carene emission within the studied population. 10% of the treesemitted mainly α-pinene and no Δ³-carene at all,whereas 20% of the trees where characterized as high Δ³-carene emitters (Δ³-carene forming >80% of totalemitted monoterpene spectrum). An intermediate group of trees emitted equalamounts of both α-pinene and Δ³-carene. The emissionpattern of trees at the area established using seeding as the artificialregeneration method differed from the naturally regenerated or plantedtrees, being mainly high Δ³-carene emitters. Some differenceswere also seen in e.g. camphene and limonene emissions between chemotypes,but sesquiterpene emissions did not differ significantly between trees. Theatmospheric concentrations at the site were found to reflect the speciesand/or chemodiversity rather than the emissions measured from any singletree, and were strongly dominated by α-pinene. We also tested theeffect of chemodiversity on modeled monoterpene concentrations at the siteand found out that since it significantly influences the distributions andhence the chemical reactions in the atmosphere, it should be taken intoaccount in atmospheric modeling.

[学科分类] 地球化学与岩石