OKUMURA Motonori, TANI Akira, KOMINAMI Yuji, TAKANASHI Satoru, KOSUGI Yoshiko, MIYAMA Takafumi, TOHNO Shoji
Isoprene emission characteristics of Quercus serrata in a deciduous broad-leaved forest
Journal of Agricultural Meteorology
We conducted field measurements of isoprene emissions from sunlit and shaded leaves of Quercus serrata, which is one of the major tree species in Japan. The measurements were conducted at the Yamashiro Flux Tower site in a deciduous broad-leaved forest. In June 2006, the isoprene emission rate (I), together with the net assimilation rate (A) and photosynthetic photon flux density (PPFD), was measured using a leaf cuvette. The experimental results demonstrated that I peaked at around noon for both the sunlit and shaded leaves, while A of the sunlit leaves peaked in the morning with a subsequent gradual decline. Consequently, the ratio of carbon emitted as isoprene to carbon fixed by photosynthesis (carbon ratio) increased during the afternoon. Data sets obtained at PPFD values higher than 1000 Êmol m-2 s-1 revealed that highly correlated with the leaf temperature. The averages of the basal emission rate IS, calculated using the Guenther algorithm (G93), were 42.9 and 20.5 nmol m-2 s-1, respectively, for the sunlit and shaded leaves of Q. serrata. Our result indicates that Q. serrata should be categorized as a strong isoprene emitter. The measured I value estimated by the G93 model was consistent with the I value within a root-mean-square (RMS) error of 4 nmol m-2 s-1, suggesting that the G93 model can be used to determine the isoprene emission response of Q. serrata to PPFD and the leaf temperature.