| Canopy interception plays an important role in water-cycle and water-balance of the forest ecological system, thus attracts much attention from eco-hydrologist and forest ecologist. The researches about canopy interception not only related to parameters definition in eco-hydrology models, but also are main contents of the forest eco-hydrology. In this study, in order to analyze canopy rainfall interception, we set four sample plots in eastern (Wangyaogou catchment) and the centre (Pailugou catchment) of the Qilian Mountains; two years of data were obtained since 2008. This study included four parts. First, determine maximum rainfall storage capacity of leaf, stick and trunk. Second, analyze the rule of canopy interception in Wangyaogou catchment. Third, use Gash model to modelling the canopy rainfall interception in Wangyaogou catchment. Fourth, use an improved model to simulate the spatial distribution of the canopy interception in Pailugou catchment. Some main conclusions can be concluded:(1) The laboratory data showed that the storage capacity of leaf, stick and trunk is different. The maximum storage capacity of leaf is between 0.023mm and 0.133mm, and the average is 0.079mm. Maximum storage capacity of stick, trunk is 0.104-0.691mm and 0.128-0.426mm, respectively. The average storage capacity of stick is 0.250mm, and the value of trunk is 0.251 mm. The storage capacity of stick is similar to trunk which is much higher than leaf. With scaling-up method, canopy rainfall storage capacity of plots was studied. In our plots, the maximum canopy rainfall storage capacity ranges from 0.553mm to 0.803mm. Compared with tree height and stand density, the leaf area index had a greatest effect to canopy rainfall storage capacity.(2) The field data in Wangyaogou catchment indicated that the percentage of canopy interception is 26.15% and the stem flow rate is 0.045% during the observation. Percentage of canopy interception decreases along with the increase of precipitation. There is an obvious power function relationship between percentage of canopy interception and precipitation. Beside, the variation of precipitation can lead to the change of the throughfall. The coefficient variation (CV) of throughfall varies from 6.6% to 156.8% as the precipitation varied; moreover, it decreases along with the increase of precipitation and the rainfall intensity.(3) Gash model was used to modelling the canopy rainfall interception in Wangyaogou catchment. The results showed that Gash model can be effectively modelling the canopy interception in our study area. During 28 rainfall events, the total canopy interception was 78.52mm while Gash model estimated value was 71.69mm.Evaporation from saturation until rainfall ceasing was the greatest within six components in Gash model and it accounted for 57.58% of total interception. There were lager errors in several results when using Gash model to estimate the single rainfall event. The error between actual observation and estimation increases when the precipitation increases. In our study area, the ratio of saturation canopy evaporation to average rainfall intensity greatestly impact Gash model.(4) Using the Quickbird image and the field observation data, an improved model was build to modelling the canopy interception in Pailugou catchment. The results showed that the amount of canopy interception in Pailugou catchment was between 97.9 and 236.6 mm and the mean interception amount was 161.8 mm in 2008. The interception percentage of Picea crassifolia forest in Pailugou catchment was between 27.92% and 58.00% and increased then decreased along with the raise of altitude. The total interception was 1.6×105m3 in 2008 while only account for 13.25% of that year's precipitation. |
PDF Full Text Request