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The isoprenoid emission of sacred fir (Abies religiosa (Kunth) Schltdl. & Cham. ), patula pine (Pinus patula Schiede, Schltdl. & Cham. ) and net-leaf oak (Quercus rugosa Née) was investigated in Mexico City during the years 2002 and 2003. Chemical compound specific emission factors were obtained for different months of the year. Net-leaf oak is an isoprene emitter whereas the other tree species emit monoterpenes. -Pinene and linalool are the main compounds emitted from sacred fir and patula pine, respectively. In general, the emission of monoterpenes is temperature dependent, whereas-pinene emission of sacred fir is controlled by light and temperature like the isoprene emission of net-leaf oak. All isoprenoids show a strong seasonality which is plant species specific. Emission factors for the conifers were high in October and low in April (sacred fir: in October and in April; patula pine: in October and in June). Isoprene emission potential of net-leaf oak was very variable in the different seasons with low source strengths in July (rainy season: ) and November (cold/dry season: ) but high in May (warm/dry season: ). The results indicate that present biogenic emission inventories of the Mexico City area have to be revised by using the new emission factors of native tree species including the seasonal impact. [Copyright &y& Elsevier]