The rationality of constructing diamster distribution model with Weibull function. in term of the weibull function characters, especially the surface of Weibull, were researched. The method to establish diamster distribution model ac cording to PRM also was provided.
Single trees sapwood scattering style and diameter classes diurnal water consumption rhythm were studied in a 48 years old Quercus variabilis stand at the east hill slope, located in the Forest Research Station of Beijing Forestry University in the water conservation area in Beijing (39°54′N, 116°28′E). Results showed that relation between trees sapwood area and diameter at breast height (DBH) was significant. Single trees daily water consumption ascended as DBH and sapwood area increased, and related significantly. Daily water consumption of different diameter class in September ascended steeply from the early morning and got the peak around 11:00 pm, and then descended till 18:00 when it got the valley slowly. Three-dimension model of daily-accumulated water consumption was acquired by scaling-up method from the typical Richards model and characteristic parameters of daily stand water consumption course were calculated from modulated Richards equation derivative: W d-it-j=(-7.147+1.174 d-i)[1-(-3 025.937+d 2.175 i)e (-0.011t-j)] 1/(1-d 0.242 i)(R=0.985 8).
