Study On Dynamic Process Of The Canopy Interception Of North Sub-tropic

The rainfall redistributions by crown layer in bamboo forests in the urban forest ecological station in Yangtze River delta were monitored, in the same time, the dynamic process of the canopy interception and the rule of the factor which influence the canopy interception were discussed. We built up the model of the canopy interception which was half experience half theories. The results as follows are got:(1) From the dynamic process of the canopy interception in the rainfall, we can find that: at the light rain class, the dynamic state change curve of the canopy interception fitted together with the dynamic state change curve of the rainfall outside the forest; At moderate and heavy rain class, the dynamic state change curve of the canopy interception deviateed the dynamic state change curve of the rainfall outside the forest, the amount of interception was nearly 0, the dynamic state change curve of accumulation with time fitted the minus index best.(2) When the canopy interception attained saturation, the interception appeared to be a negative. The formation and the ending time of the throughfall and stemfall in forests were all late to outside the forests. The wave crest and trough of throughfalls and stemfalls in forests were generally appeared slower than outside, so were the vibration frequency of throughfalls, rates of dynamic change curve of accumulative throughfalls and stemfalls fitted multinomials well.(3) The change of leaf area index effected the canopy interception not obviously; it mainly embraced in the wave crest and the formation time, With leaf area increasing, the wave crest of canopy interception decreased, the formation time generally run behind, and the wave crest value of stemfalls increased.(4) canopy interception,stemfalls and throughfalls separately changed in the range of 0.21～4.55mm,0～105.88mm,0～2.8 mm, the rate of canopy interception,stemfalls and throughfalls separately changed in the range of 1.3%～100%,0～96.3%,0～11.8%; canopy interception,stemfalls and throughfalls all years long separately were 171.7mm,864.78 mm,74.3mm, the rate of canopy interception,stemfalls and throughfalls separately were 15.5%,77.9%,6.7%.(5) Along with the increment of the rainfall, canopy interception increased first then changed to a stability value, throughfalls increased linearly, stemfalls increased from fast to slow, with the increment of rainfall intensity, throughfalls increased while canopy interception and stemfalls decreased. With the increment of leaf area index, canopy interception and stemfalls present well linear relation, but the throughfalls were contrary. With the dry degree increasing, the canopy interception increased while throughfalls decreased. The stemfalls of different chest path level in light rain were very obvious, and they turn obvious in medium and heavy rain.(6) We used half experience half theories formula in the model of canopy interception. By validating, the rate of max error was 32.9%while of mix error was 0.1%, the rate of error of canopy interception in the year was 7.3%, which was less than 10%, it accord with the demand.