HR: 0800h
AN: H31E-0699    [Abstracts]
TI: Modeling of Radiation Transport in the Plant Canopy Reflects the Change in Phenology
AU: * Maruyama, A
EM: maruyama@affrc.go.jp
AF: National Agricultural Research Center for Kyushu Okinawa Region, 2421, Suya, Koshi, Kumamoto, 8611192, Japan
AU: Kuwagata, T
EM: kuwa@affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 3058604, Japan
AB: Solar radiation in a plant canopy plays an important role in the energy balance on both the plant leaves and soil surface, which controls the water and heat transfer in the soil-plant-atmosphere continuum. A simple model was derived from the two-stream model to estimate two important factors characterizing radiation in a plant canopy, namely, transmissivity of the canopy (τ) and the albedo of the canopy (ref), from the absorption coefficient of leaves (α) and leaf inclination factor (F). To clarify the seasonal variation in α and F with plant growth, season-long observations were conducted in rice fields during three different cropping seasons. Values of α were almost constant throughout the growing period; however, values of F tended to increase with change in phenology. Values of F were larger than 0.5 (the theoretical value for random leaf distribution) in the late growth stage due to the alterations in leaf geometry with the change in leaf inclination angle along a more horizontal axis after flowering, while in contrast, values of F were less than 0.5 in the early growth stage due to the distribution bias of leaves. Seasonal variation in F during different cropping seasons could commonly be expressed as a function of developmental stage (DVS). Using this function, τ and ref could be estimated with more accuracy. The proposed radiation model and function is expected to be applicable in more accurate evaluation of the water vapor and heat transfer in the soil-plant-atmosphere continuum that reflects the change in plant phenology.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 1814 Energy budgets
DE: 1818 Evapotranspiration
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting