Fluxes of biogenic volatile compounds between plants and the atmosphere

The nose can reveal much qualitative information about the release of organic volatiles by plants, but since it is preferentially sensitive to certain terpenes. . . and rather insensitive to others. . . analyses with a gas chromatograph are needed to obtain a quantitative picture of the volatile organics present in the air at all times. Thus we easily detect the aromaticity of a deciduous forest in autumn, and especially the sweet odor of the leaf litter on the forest floor, and we can tell a coniferous forest at a distance. But we are unprepared for the fact that an oak forest produces virtually as many aromatics as a pine forest, only of a lower odor level.Rasmussen and Went (1965)