HR: 1340h
AN: B43A-0239    [Abstracts]
TI: Soil respiration model with a plant canopy: Hydrological and thermal effects of canopy characteristics on soil respiration
AU: * Tanaka, K
EM: Ktanaka@jamstec.go.jp
AF: Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showamachi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Hashimoto, S
EM: shojih@ffpri.affrc.go.jp
AF: Department of Forest Site Environment, Forestry and Forest Products Research Institute Incorporated Administrative Agency, 1 Matsunosato, Tsukuba, 305-8687 Japan
AB: A soil-plant-air continuum multilayer model was developed to simulate soil respiration. The model included the processes of CO2 gas transfer and production in the soil. The model can be used to investigate the effects of three canopy characteristics on soil respiration: leaf area index, the maximum rate of carboxylation, and the vertical profile of leaf area density. Numerical experiments were performed using above-canopy hydrometeorological variables including seasonal changes related to a dry season with strong evaporative demand (high solar radiation and high temperature) and a rainy season with weaker evaporative demand. The results suggest that canopy characteristics can limit soil respiration because of thermal and hydrological effects. An increase in leaf area decreased soil respiration by decreasing soil temperature through a reduction in net radiation to the soil surface, and by decreasing soil moisture with an increase in canopy transpiration. An increase in the maximum rate of carboxylation decreased soil respiration because it decreased soil moisture by increasing canopy transpiration; there was little thermal effect on soil respiration. A canopy with a denser leaf area in the upper layers created a faster wind velocity in the lower portion and on the ground than did a canopy with the same leaf area index, but with a denser leaf area in the lower layers. The faster wind velocity significantly decreased soil moisture at the soil surface and decreased soil temperature through an increase in soil evaporation; these effects decreased soil respiration. The hydrological effects of the three parameters were most evident in the dry season, while the thermal effects were evident year-round.
DE: 0428 Carbon cycling (4806)
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0466 Modeling
DE: 0476 Plant ecology (1851)
DE: 0560 Numerical solutions (4255)
SC: Biogeosciences [B]
MN: Fall Meeting 2005