Scaling-up method for stand water consumption of Quercus variabilis water conservation forest

Abstract

Single tree s sapwood scattering style and diurnal water consumption rhythm for different diameter classes were studied in a 48-year-old Quercus variabilis stand, water protection forest in Beijing. Results showed that the tree s sapwood area was closely related to diameter at breast height (DBH). Single tree s daily water consumption ascended as DBH and sapwood area increased. Daily water consumption of different diameter classes in September ascended steeply in the early morning and reached the peak around 11:00, and then descended slowly to the valley at 18:00. The course of daily accumulated water consumption was in accordance with a typical Richards model (R=0.985,8). Parameters of diameter-time equation for scaling-up can be achieved by parameter-recovering method in the gradient of all diameter classes and at any time of a day, characteristic parameters of the course of daily stand water consumption were calculated from a modulated Richards equation derivative: W_diti=(-7.147+1.174^d_i)[1-(-3,025.937+d^_i2.175).e^(-0.011t_j)]^{1/(1-d_i0.242)}