1To clarify the utility of spectral vegetation indices (VIs) for estimating light conversion 2 efficiency () in Japanese coniferous forests, we investigated the relationships between six 3 VIs (NDVI, EVI, SAVI, PRI, CI, and CCI) and in two mature monospecific forests of 4 deciduous conifer (Japanese larch) and evergreen conifer (Japanese cypress) and one young 5 mixed stand of deciduous conifer with evergreen undergrowth (hybrid larch and dwarf 6 bamboo). In each forest canopy, we measured seasonal variations in CO 2 flux, radiation 7 environment, and visible-near-infrared spectral reflectance during 1 or 2 growing seasons. 8We calculated as gross primary production (GPP) divided by the difference between 9 incoming and reflected photosynthetically active radiation (PAR). VIs and under clear skies 10 were averaged between 11:00 and 13:00 JST and their relationships were analyzed. 11In the larch forest, all calculated VIs were positively correlated with , and the highest 12 correlation was that with CCI. Because of effects of extreme reduction in PRI in autumn with 13 needle yellowing, the correlation of and PRI was relatively small in this forest. In the 14 cypress forest, on the other hand, no significant correlation was found except with PRI and 15 CCI. The highest correlation in this forest was that with PRI, suggesting that the leaf biomass-16 related VIs based on near-infrared reflectance are not sufficient for estimating of evergreen 17 forest. In the mixed forest, with relatively sparse vegetation cover, all VIs were significantly 18 correlated with , but the best correlation was that with SAVI, possibly owing to the reduction 19 in the effect of the reflectance from background soil. Correlation analysis of the pooled data 20 3 from all forests showed the highest correlation between and PRI. These results indicate that 1 PRI is an effective VI in the remote estimation of in both deciduous and evergreen forests, 2 although there are some sensitivity differences between vegetation types. 3 4