Water transfer from soil through plants to the atmosphere in willow energy forest
1984
Kowalik, P.J. | Eckersten, H.
A new continuous simulation model for transpiration from energy forest is formulated and solved numerically: the model describes interrelations of water state and transpiration in the soil-plant-atmosphere system under realistic field conditions and specifically includes the water stored in the plant. In the well-known Penman-Monteith method for transpiration determination, the surface temperature and humidity are eliminated by combining the bulk aerodynamic and heat budget relationships. In the method proposed here, the surface values are not eliminated but are computed by an iterative method, using empirically established stomatal resistance for the considered type of vegetation. Driving input variables (continuously recorded) are air temperature and relative humidity, solar radiation and soil water potential. Input also includes the values of aerodynamic resistance and plant liquid water resistance as well as time-invariant relations between leaf water potential and plant water content, stomatal resistance and leaf water potential, stomatal resistance and solar radiation, and soil-root hydraulic resistance and soil water potential, respectively. The simulation runs with a fixed time interval of 1 min. The model describes the changes in the diurnal course of transpiration, stomatal behaviour, leaf water potential and leaf canopy temperature of willow plantations. The calculated daily cumulative values of transpiration (including evaporation of intercepted water) compared well with measured values observed in lysimeters in Salix stands at Studsvik (Sweden). The model has wider application than simply for willow; a change in the computer simulation from one plant species to another may be achieved by altering the root, xylem and leaf parameteres of the model.
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