HR: 1340h
AN: B43B-0285    [Abstracts]
TI: Estimation of Light Use Efficiency of Japanese Larch Forest Using Remote Sensed Vegetation Indices
AU: * Nakaji, T
EM: nakaji.tatsuro@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Saigusa, N
EM: n.saigusa@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology, 16-1 Onogawa, Tsukuba, 305-8569 Japan
AU: Fujinuma, Y
EM: fujinuma@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Oguma, H
EM: oguma@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AB: We investigated seasonal variations in the photochemical reflectance index (PRI) and its relation to the photosynthetic light use efficiency (LUE) in mature Japanese larch ( Larix kaempferi) forest throughout the growing season from June to October 2003. The observations were carried out for both scales of needles and canopy. In the needle-scale observation, daily mean value of PRI showed seasonal variation, strongly correlated with the chlorophyll concentration and carotenoid/chlorophyll ratio of the needles. During the green period from early June to late September, the hourly values of both PRI and LUE in canopy-top needles showed significant midday depression, and were positively correlated. In late October, however, since the PRI of senescent needles tended to increase slightly at midday in contrast to the LUE, this correlation became negative. Even before autumn senescence, the sensitivity of needle PRI to LUE changed with the season. Correlation analysis indicated that the slope and intercept of the regression line between hourly PRI and LUE (LUE = slope * [PRI - intercept]) increased during summer, with peaks in July and August, respectively. The seasonal change in slope was strongly correlated with the foliar photosynthetic pigment concentration, nitrogen concentration, air temperature, and the daily mean value of the normalized difference vegetation index (NDVI). The value of the intercept was positively correlated with the daily mean PRI. These results suggest that although diurnal change in LUE cannot be estimated quantitatively from PRI on its own throughout the growing season, the combined use of PRI and other variables such as foliar N, pigments or NDVI could improve the remote evaluation of seasonal changes in LUE of deciduous tree leaves. Also in the canopy scale monitoring, similar seasonal drift was observed in the regression lines between hourly PRI and LUE of gross CO₂ flux in clear days. We try to develop the empirical regression model to estimate LUE from remote sensed vegetation indices.
DE: 0428 Carbon cycling (4806)
DE: 0466 Modeling
DE: 0476 Plant ecology (1851)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: Fall Meeting 2005