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).
Using thermal dissipation probe(SF-G), a sample tree’s diurnal sap flow velocity and sap flow density at different trunk heights were monitored in the Quercus acutissima plantation in the Forestry Centre of Taishan Academy of Forestry Science in spring and autumn. 5 days data both in spring and autumn were selected, and spatial variation of trunk water pondage and sap flow was analyzed. In spring, the peak value was higher and fluctuated acutely, and the peak time appeared early and lasted longer than that in autumn. Sap flow velocity at upper trunk section was higher than that at mid and lower trunk section. In autumn, however, sap flow flux at the three trunk sections was very small and similar. Sap flow movement was lagged in order from the lower trunk to upper trunk by 60～120 min in autumn. Spring trunk poundage fluctuated sharply and extended greatly than that in autumn. The relative trunk water restoring time in spring was about 20 h, and 10～12 h longer than that in autumn.
